bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in acetylcholine receptor distribution and binding properties at the neuromuscular junction during aging
Authors: Smith Dean O. , Williams Kevin D. , Emmerling Mark 
Published: April 2003

AbstractJunctional and extrajunctional acetylcholine receptors were characterized in diaphragm muscle obtained from mature adult and aged rats. Rhodamine‐conjugated α‐bungarotoxin was used to visualize receptor localization. At this level of resolution, there were no major changes in receptor distribution, and nerve terminals were consistently associated with receptors and vice versa. Specific binding characteristics were assayed by measuring 125I‐α‐bungarotoxin binding. Maximal binding to intact junctional and extrajunctional tissue samples was greater in the older rats. The association rate constant in minced tissue decreased in the older animals. Retardation of the initial rate of toxin binding by d‐tubocurarine was described by a two‐component nonlinear Hofstee plot; values of Ki were about the same for both age groups, but there was a significant shift towards the low‐affinity values in the aged rats. Miniature end‐plate currents (m.e.p.c.s) were recorded under voltage‐clamp conditions before and after AChE inhibition. When AChE activity was inhibited m.e.p.c. amplitudes and decay time‐constants increased in both age groups. The magnitude of these increases was larger in the older animals. Inhibition of AChE did not affect mean channel open time, which was estimated from spectral analyses of ACh‐induced membrane noise. Lipid composition was assayed in whole muscle and isolated sarcolemma. Muscle cholesterol concentration rose 15–20 percent, but phospholipid concentrations were maintained. However, neither cholesterol, phospholipid levels, nor membrane fluidity changed significantly with age in isolated sarcolemmal membrane fractions.These data indicate that the numbers of junctional and extrajunctional receptors increase with age. In the junctional region, this is quite likely due to an expanded field of receptors and not an increased density. This is associated with an increased fraction of receptors with lower binding affinity during aging. These changes apparently are not caused by major changes in membrane fluidity or lipid composition.
Cell‐type specific effects of N‐methyl‐d‐aspartate on biochemical differentiation of subcortical neurons in culture
Authors: Patel Ambrish J. , Hunt Anthony , Sanfeliu Coral 
Published: April 2003

AbstractThe possible involvement of N‐methyl‐d‐aspartate (NMDA) receptors in the biochemical differentiation of cultured neurons derived from the medial frontal part of the forebrain containing the septum‐diagonal band region was studied in terms of the activities of enzymes important in the synthesis of neurotransmitter compounds. The activity of choline acetyltransferase (ChAT) was used as a marker for cholinergic neurons, glutamate decarboxylase (GAD) for GABAergic neurons and phosphate‐activated glutaminase (GLNase) and aspartate aminotransferase (ASP‐AT) for glutamatergic neruons, while lactate dehydrogenase (LDH) was included as an ubiquitous enzyme. The exposure of cultures to a depolarizing concentration of K+ (40 mM) for the last 3 days (i.e. between 2 and 5 days in vitro) significantly enhanced the expression of ChAT, GAD and GLNase activities, but high K+ caused little alteration in the activities of ASP‐AT and LDH. On the other hand, treatment with NMDA markedly elevated the specific activities of GAD and GLNase only, and the compound had no significant effects on the activities of ChAT, ASP‐AT and LDH enzymes. The enhancements of the specific activities of GAD and GLNase were completely blocked by the NMDA receptor antagonist, 2‐amino‐5‐phosphonovaleric acid, and by the NMDA receptor‐linked Ca2+ ion channel blocker, MK‐801. On the basis of the present findings it is concluded that, (a) contrary to an earlier proposal, ASP‐AT does not appear to be a good marker for the glutamatergic neurons, (b) the failure of the subcortical cholinergic neurons to respond by an increase in ChAT activity to NMDA may indicate that these nerve cells lack NMDA subtype excitatory amino acid receptors, and (c) as the septal GABAergic input in the hippocampus is involved in the modulation of long‐term potentiation, the presence of NMDA receptors on these neurons would now suggest that NMDA receptors are linked to both the initiation and the modulation of hippocampal plasticity in the mammalian brain.
Appearance and localization of dystrophin in normal human fetal muscle
Authors: Prelle A. , Chianese L. , Moggio M. , Gallanti A. , Sciacco M. , Checcarelli N. , Comi G. , Scarpini E. , Bonilla E. , Scarlato G. 
Published: April 2003

AbstractWe studied the localization of dystrophin in normal human fetal muscle by immunohistochemistry. Our results show the appearance of dystrophin at week 11 and a progressive organization of the protein along membrane in the following weeks of gestation. At week 22 almost all fibers show a clear membrane immunostaining. Concomitant analysis of muscle fiber‐type composition reveals no correlation between progressive appearance of dystrophin and muscle fiber‐type differentiation. Our findings suggest that synthesis and localization of dystrophin in developing human skeletal muscle is time‐related and probably independent of neuronal influences.
Expression of c‐myc and c‐fos oncogenes in different rat brain regions during postnatal development
Authors: Parma Diana L. , Benasayag Silvia J. , Szijan Irene 
Published: April 2003

AbstractWe have studied the expression of c‐myc and c‐fos proto‐oncogenes in various areas of the central nervous system during postnatal development, c‐myc mRNA levels increased during the first 5 days and then decreased over the next 15 days in all nervous regions studied, c‐fos mRNA levels changed in a different way in four brain areas. While in cerebral cortex and cerebellum there was a sharp decrease during the first 10 days, in white matter and hypothalamus c‐fos transcript levels remained high during the same period, decreasing at a later stage.Changes in oncogenes mRNA levels are related to various developmental events, such as neurite growth, myelination and cell proliferation. The dissimilar patterns of c‐myc and c‐fos expression suggests that they play different functions in CNS maturation, c‐myc mRNA levels are temporally related to active neurite growth and to cell proliferation. Changes in c‐fos mRNA correlate in time with early developmental processes and also with those occurring at later stages, such as myelination.
Elevated potassium prevents neuronal death but inhibits network formation in neocortical cultures
Authors: Baker R.E. , Ruijter J.M. , Bingmann D. 
Published: April 2003

AbstractChronic depolarization is inimical to neuronal growth and synaptogenesis so that spontaneous action potential generation appears to be required for the normal cytomorphological maturation of neocortical networks. The efficacy of 25 mM K in suppressing spontaneous bioelectric activity was monitored by extra‐ and intracellular recording from the explants. Intracellular recording from individual neurons showed that membrane potentials were reduced to ca −30 mV in potassium cultures but rapidly repolarized to ca −50 mV when returned to normal growth medium. Though action potentials could be readily evoked from these explants, spontaneous discharges and postsynaptic potentials were absent from potassium‐treated cultures. Both spontaneous bioelectric activity and postsynaptic potentials returned to the cultures by 5 days after returning the explants to normal growth medium. Extracellular recordings also showed that the explants were bioelectrically silent in the presence of 25 mM K or 25 mM K plus tetrodotoxin. In contrast to tetrodotoxin alone, bioelectric activity was absent when the cultures (with or without tetrodotoxin) were returned to normal growth medium. The explants gradually began to evince spontaneous bioelectric activity between 3 and 5 days after being returned to normal growth medium. Massive cell death induced by chronic exposure to tetrodotoxin was totally prevented by concomitant addition of 25 mM potassium, though these explants were significantly thinner than controls due to a large decrease in neuropil.We conclude that chronic depolarization of neonatal cortical explants by potassium results in a delayed return of spontaneous bioelectric discharges. Chronic depolarization results in a retardation of network formation in these explants apparently due to a lack of neurite and/or synapse formation. These effects are reversible with function returning to the explants over a period of several days.
Some observations on the localization of hyaluronic acid in adult, newborn and embryonal rat brain
Authors: Bignami A. , Asher R. 
Published: April 2003

AbstractHyaluronic acid was localized in acetone‐fixed cryostat sections of brain and spinal cord obtained from adult, newborn and embryonal rat. The sections were incubated with glial hyaluronatebinding protein (GHAP) of human origin and the protein was visualized by indirect immunofluorescence with monoclonal antibodies raised to human GHAP and not staining rat brain by immunofluorescence. GHAP is a brain extracellular matrix (ECM) glycoprotein, approximately 60,000 molecular weight, which is structurally related to the HA‐binding region of cartilage ECM proteins. The distribution of hyaluronate in adult brain white matter and cerebellar cortex was similar to that previously reported for GHAP. In both cases, the reaction product formed a mesh surrounding myelinated axons and granule cells. Hyaluronate was also found in parts of the brain that did not contain GHAP. A finely reticulated mesh was observed in the neuropil between cell bodies in cerebral cortex and basal ganglia. Scattered cortical neurons were surrounded by a rim of reactive material. Perineural staining was the rule rather than the exception in spinal cord anterior horn motoneurons, inferior olivary nucleus, large bulbar reticular neurons and dentate nucleus of cerebellum. The only part of the brain which appeared relatively free of hyaluronate was the molecular layer of the cerebellum. In newborn and embryonal rat, the densely packed cell bodies in cerebral gray matter, periventricular germinal layer and external granular layer of cerebellum were surrounded by hyaluronate. Small droplets of hyaluronate were observed inbetween the cylindrical epithelial cells lining the neural tube in 11 day embryos. Non‐myelinated fiber tracts and the molecular layer of the developing cerebellum were relatively unstained. No hyaluronate was detected in the ependyma lining the cerebral ventricles and the central canal of the spinal cord.
Effects of pentylenetetrazol‐induced seizures on dopamine and norepinephrine levels and on glucose utilization in various brain regions of the developing rat
Authors: Hamdi Ghéziel El , Boutroy Marie‐Jeanne , Nehlig Astrid 
Published: April 2003

AbstractLevels of dopamine and norepinephrine were measured in seven brain areas after 60 min of sustained seizure activity induced by intraperitoneal repetitive timed administrations of pentylenetetrazol in rats at 10, 14, 17 and 21 days of postnatal life. The tissue levels of norepinephrine were markedly reduced in the majority of brain structures, except for striatum at 10 and 14 days. Conversely, dopamine concentrations increased in many areas and at various ages, except in cerebral cortex at 10 and 14 days and in midbrain between 14 and 21 days. PTZ seizures induced marked increases over control levels in the rates of glucose utilization, measured by the quantitative autoradiographic [14C]2‐deoxyglucose method, in all dopamine‐ and norepinephrine‐innervated areas studied at 10 and 14 days, except in cerebellar cortex at both ages and in frontal cortex and anteroventral thalamus at 14 days. At 17 and 21 days, glucose utilization remained increased over control levels in some areas, mainly in catecholaminergic cell groupings such as substantia nigra, ventral tegmental area and locus coeruleus, but was significantly reduced in cortex, caudate nucleus and thalamus, and similar to control rates in other regions.The present results suggest that pentylenetetrazol‐induced seizures lead to a simultaneous increase in functional activity of norepinephrine neurons and an inhibition of dopaminergic‐mediated neurons. They also confirm the maturation of connections, of metabolic activity and of neurotransmitter interaction within the brain, occurring mainly during the third week of postnatal life, paralleled by an increased selective vulnerability of some regions to this kind of insult.
Neuritogenesis on collagen substrates. Involvement of integrin‐like matrix receptors in retinal fibre outgrowth on collagen
Authors: Carri Néstor G. , Rubin Kristofer , Gullberg Donald , Ebendal Ted 
Published: April 2003

AbstractExtracellular matrix molecules such as laminin, fibronectin and collagen promote neurite out‐growth in vitro. We have investigated the capacity of hydrated gels of collagen types I–III and monomeric collagen types I–VI on plastic surfaces to support neuritogenesis. The attachment and survival of explants from the day 6 chick embryo were studied and neurite outgrowth measured as mean elongation rate and maximal neurite length. Collagen types I and III, both as three‐dimensional gels or as native monomers supported neuritogenesis equal to or better than laminin. Collagen type V also supported neurite out‐growth although less effectively. Collagen types II, IV and VI, as well as denatured collagens of all types tested, did not support outgrowth. The monoclonal anti‐β1 integrin antibody (CSAT), as well as rabbit polyclonal antibodies directed to the integrin β1‐chain, effectively inhibited neurite outgrowth on permissive collagenous substrata, indicating that collagen‐binding integrins were involved in the neuritogenesis. These β1‐integrins were independent of Arg‐Gly‐Asp (RGD) since neurite formation proceeded in the presence of synthetic RGD‐containing peptides. Fluorescence immunohistochemistry revealed the presence of the integrin β1‐chain on the outgrowing neurites. The results suggest a possible function of collagen and collagen‐binding integrins in the development of the visual system.
Development of the cholinergic fibres innervating the cerebral cortex of the rat
Authors: Kiss Jozsef , Patel Ambrish J. 
Published: April 2003

AbstractThe ontogeny of innervation of the cholinergic fibres from the basal forebrain into the cingulate, frontal, parietal and piriform cortices of the rat has been examined using a modified histochemical method of acetylcholinesterase (AChE). The method produced crisp fibre staining with enhanced visibility and a clear back‐ground, and a pattern of the distribution of these fibres was comparable to that achieved by choline acetyltransferase (ChAT) immunocytochemistry. In the rat, the AChE‐stained fibres developed progressively from the deep cortical white matter towards the cortex itself. In general, a few AChE‐positive fibres were seen in the subcortical white matter and the cingulum bundle, entering into the cerebral cortex by about 5 postnatal days. The number of these AChE‐positive processes increased dramatically during the following two weeks. Thereafter, the general appearance of the overall pattern of distribution of the AChE fibres changed little, but the staining density became gradually more intense and by about 28 days after birth it was virtually indistinguishable from that in the adult. The onset and the development of the AChE‐positive fibre network varied considerably between individual cortical regions, and indicated, in general, an anterior to posterior gradient. Within the dispersed AChE fibre network in the cerebral cortex, three bands of relatively enriched cholinergic processes, namely the deep cortical, mid‐cortical and superficial layers, developed in an ‘inside‐out’ fashion. The exact position of some of these AChE‐rich bands varied from one cortical region to another and during development. A striking correlation during ontogeny was observed in the cerebral cortex between the changing patterns of AChE fibre network and the activity of ChAT, the enzyme synthesizing acetylcholine. The present findings can also provide an important anatomical baseline for future studies related to the factors controlling the expression of ChAT activity and the development of cholinergic neurotransmitter system in the rat.
Glial fibrillary acidic protein and its encoding mRNA exhibit mosaic expression in a glioblastoma multiform cell line of clonal origin
Authors: Bocchini V. , Beccari T. , Arcuri C. , Bruyere L. , Fages C. , Tardy M. 
Published: April 2003

AbstractThe expression of two astroglial differentiation markers, vimentin and glial fibrillary acidic protein, was investigated in a previously established human glioma cell line of clonal origin (GL15). Vimentin immunolabelling was homogeneously expressed in all cells. Glial fibrillary acidic protein and its encoding message, investigated by immunocytochemistry and in situ hybridization, showed a mosaic‐like expression. Only 30% of the cell population expressed glial fibrillary acidic protein and its mRNA. Western and Northern blots performed for both markers confirmed the presence of both proteins and messages, and their level was correlated with the observed antigenic and molecular probe labelling. The overall antigenic pattern suggests that GL‐15 cells do not belong to the O‐2 A progenitor cell lineage and may arise from a clonal expansion of astrocyte precursors.
The pH of jimpy glia is increased: Intracellular measurements using fluorescent laser cytometry
Authors: Knapp Pamela E. , Booth Charles S. , Skoff Robert P. 
Published: April 2003

AbstractThe jimpy mutation lies in the gene which codes for myelin proteolipid protein, and the brains and spinal cords of jimpy mice contain little myelin and no measurable proteolipid protein. It has been thought that the mutation affected only the myelin forming oligodendroglial cells, but there is now considerable evidence that astroglia are also a target of the mutation since jimpy astrocytes exhibit a prominent gliosis along with defects in metabolism and proliferation. Because cell proliferation is associated with an increase in intracellular pH, we investigated whether the pH of jimpy glia was abnormal. Using a pH sensitive fluorescent dye and a laser cytometry system we measured the intracellualr pH of individual cells in cultures derived from both jimpy and normal brains. The relative pH of flat astrocytes in jimpy cultures was higher than in normal cultures by an average of 0.24 pH units, and these increased values were evident 2–3 days after plating. At this in vitro age the cultures contain only a few oligodendrocytes, none of which express detectable proteolipid protein. The pH of the process‐bearing cell population, which contains the oligodendrocytes as well as some astrocytes and presumptive glial precursors, was also increased but not until 7 days in culture.The finding that a mutation in the myelin proteolipid protein gene can alter the normal pH of astrocytes is quite unexpected since, as far as is known, astrocytes do not make proteolipid protein. These results and others discussed in this paper support the hypothesis that either proteolipid protein itself, or some other product of the gene, may have an important role in central nervous system development.
Microglia‐derived plasminogen enhances neurite outgrowth from explant cultures of rat brain
Authors: Nagata Koichi , Nakajima Kazuyuki , Takemoto Nagisa , Saito Hiroshi , Kohsaka Shinichi 
Published: April 2003

AbstractRecently, we reported the production and secretion of plasminogen (Pg) in cultured rat brain microglia [Nakajima et al., (1992) Fedn. Eur. Biochem. Socs Lett.308, 179–182]. To investigate the physiological significance of Pg, we determined the effect of Pg on neurite outgrowth of cultured neocortical explants of an embryonic rat brain in serum‐free chemically defined medium. Pg markedly enhanced the neurite outgrowth. Although plasmin, which is derived from Pg by activation by urokinase (UK), had a similar effect in this explant culture system, UK itself did not show any effect. Furthermore, we studied the characteristics of Pg binding to cultured neocortical neurons dissociated from an embryonic 16‐day‐old rat brain by using 125I‐Pg. Specific binding of Pg to neocortical neurons was detected and Scatchard plot analysis revealed high‐ and low‐affinity binding sites on the neurons. The estimated dissociation constants of high‐ and low‐affinity binding sites were approximately 16.1 and 124.2 nM, respectively. These results suggest that microglia‐derived Pg plays certain roles in the regulation of neurite extension through binding to the surface of neocortical neurons.
Relationship between ischemia and ischemic neuronal necrosis to astrocyte expression of glial fibrillary acidic protein
Authors: Petito Carol K. , Halaby Issam A. 
Published: April 2003

AbstractIt is not entirely clear whether the proliferative changes in astrocytes following cerebral ischemia are in response to neuronal injury or are secondary to the direct effects of ischemia on the astrocytes. Therefore, the following study examined the relationship between post‐ischemic astrocytosis with the extent of neuronal necrosis and the severity of the ischemia. Astrocyte reactivity was assessed by alterations in glial fibrillary acidic protein (GFAP), using immunohistochemistry and evaluation by optical density analysis. Cerebral ischemia was produced in rats by temporary occlusion of the carotid and vertebral arteris for 2,10 and 30 min. This results in damage to the CA1 neurons after a characteristic delay of several days, the duration of which is inversely proportional to the severity of the ischemia. CA3 neurons are resistant to the ischemia and do not suffer permanent injury. The results showed that GFAP immunoreactivity significantly increased in the CA1 region after all three ischemic intervals but the rise of GFAP in the CA3 area reached significance only after 30 min of ischemia. The peak and duration of the GFAP increases thus correlated with the extent and the maturation of the neuronal necrosis. This suggests that with mild injury (2 and 10 min ischemia), post‐ischemic astrocytosis is closely related to its neuronal environment rather than to the ischemic insult itself. Furthermore, the results showed an initial decrease in and delay of the subsequent GFAP rise. This initial decline in GFAP and the delay in its rise have both been identified in other models of brain injury and may be related in part to transient astrocyte swelling as well as to a finite interval required for sufficient increases in transcriptional activity to affect a noticeable rise in GFAP immunoreactivity.