bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decrease in the number of lower affinity (type II) nerve growth factor receptors on embryonic sensory neurons does not affect fiber outgrowth
Authors: Stach Robert W. , Wagner Barbara J. 
Published: January 2005

AbstractNerve growth factor binds to two different specific receptors on responsive cells. The relationship of these two receptors is not fully understood at this time. We have studied the binding of labeled NGF to a different strain of white leghorn chicken embryo dorsal root ganglionic cells. The equilibrium dissociation constants for the two sites (K = 4.1 ± 1.8 × 10−11M, K = 1.0 ± 0.8 × 10−9M) are identical to those obtained previously. Also, the number of type I sites per cell (3.8 ± 1.3 × 103) is the same as that previously determined. However, the number of type II sites per cell (1.9 ± 1.3 × 104) is significantly different than that previously determined. This 2.5‐fold decrease in the number of type II sites does not affect the concentration of NGF needed to obtain maximal fiber outgrowth from explanted sensory ganglia. The rate of association (1.2 ± 0.2 × 107 M−1 sec−1 at 22°C) of labeled NGF with receptors on sensory neurons from this different strain of chickens is identical to that previously obtained.The rate of association of NGF with its receptors on sensory neurons was also determined at 4°C. This rate constant (2.1 ± 1.1 × 106 M−1 sec−1) along with the rate constants obtained at 22° and 37°C were used to determine an activation energy for the binding of NGF to its receptors. The activation energy obtained (16.2 kcal/mole) suggests that binding is not a diffusion‐controlled process.
Immunoselection of oligodendrocytes by magnetic beads. I. Determination of antibody coupling parameters and cell binding conditions
Authors: Meier D. H. , Lagenaur C. , Schachner M. 
Published: January 2005

AbstractOligodendrocytes from early postnatal mouse cerebellum were isolated using polyacrylamide‐coated magnetic beads carrying monoclonal antibody to 04 cell surface antigen. Oligodendrocytes were enriched to a purity of 91 ± 4% starting from a mixed cell population containing approximately 1.5% antigen‐positive oligodendrocytes. Viability of 04 antigen‐positive oligodendrocytes was approximately 90% as judged by exclusion of trypan blue. Oligodendrocytes were recovered after detachment from the beads with a yield of 19 ± 6% and after collection by centrifugation onto glass coverslips with yields of approximately 6% of all 04 antigen‐positive cells. The final cell yield of oligodendrocytes is approximately 8 × 105 cells/gram fresh cerebellar tissue.
Immunoselection of oligodendrocytes by magnetic beads. II. In vitro maintenance of immunoselected oligodendrocytes
Authors: Meier D. , Schachner M. 
Published: January 2005

AbstractOligodendrocytes isolated by immunoaffinity on magnetic beads using a monoclonal antibody to oligodendrocyte cell surfaces were obtained with a purity of 91 ± 4% [see companion paper, Meier et al, 1982]. Contaminating cells consisted mostly of tetanus toxin‐positive neurons with small cell bodies. Very few glial fibrillary acidic protein‐positive astrocytes and fibronectin‐positive fibroblasts or fibroblast‐like cells could be detected by indirect immunofluorescence. Macrophages, as identified by their characteristic morphology, were rarely detectable in the cultures. With increasing time in culture, the degree of homogeneity of the cultured oligodendrocytes increased slightly, while the cell density of oligodendrocytes decreased drastically within the first week of culture. Cultures of immunoselected oligodendrocytes with a lower degree of purity showed a better survival of oligodendrocytes, but a considerable reduction in purity after three weeks in culture, probably due to overgrowth of nonoligodendroglial elements.
Sequestration of tetanus toxin in developing neuronal cell cultures
Authors: Yavin Ziva , Yavin Ephraim , Kohn Leonard D. 
Published: January 2005

AbstractCultivation of pure populations of cerebral cells and the unambiguous identification of the neuronal and glial elements is a prerequisite for studying biochemical parameters associated with the developing nervous system under in vitro controlled conditions. We now report on sequestration of tetanus toxin, an exclusive marker for the neuronal cell surface, into a cellular compartment which prevents its release by neuraminidase. This compartment is associated with cellular elements remaining after detergent extraction of neuronal cells grown in monolayer cultures. Toxin sequestration into this compartment is preceded by a neuraminidase‐sensitive receptor mediated binding process which can be correlated with the appearance of lipid‐bound sialic acid in developing neuronal cultures.
Growth zone of the juvenile goldfish retina revealed by fluorescent flat mounts
Authors: Negishi K. , Teranishi T. , Kato S. 
Published: January 2005

AbstractThe retinas of juvenile goldfish (Carassius auratus) were processed for fluorescence microscope studies with flat mounts. The fish were reared in a laboratory aquarium for 1–3 months after either one class of retinal dopaminergic (DA) cells or indoleamine‐accumulating (IA) cells had been destroyed by intravitreal injection of 6‐hydroxydopamine (6‐OHDA; 2.5 m̈g) or 5,7‐dihydroxytryptamine (5,7‐DHT; 2.5 μg). The fish grew 10–12 cm in body length on the average for 3 months. The retinas were isolated at various survival times after pretreatment with 6‐OHDA or 5,7‐DHT. To improve detection of the cells, a mixture of noradrenaline (NA; 0.5 μg) and 5,6‐DHT (0.5 μg) was intravitreally injected into the eyes 2 hr before enucleation. Retinal growth occurred by cell proliferation at the circumferential margin distal to the retinal center. In this process, DA and IA cells were added in concentric rings, with a rate of cell accretion of approximately 12 cells per day, estimated from the mean cell density in the growth zone (about 252 μg width) over a 3‐month period. In order to compensate for loss of dopaminergic innervation induced by intravitreal 6‐OHDA, the proliferation rate appeared to be facilitated significantly compared to that in normal retinas, and long and centrally extending processes were found to emerge from the DA cells formed earliest after intravitreal injection of 6‐OHDA.
Regulation of neurite growth in purified retina neuronal cultures: Effects of PNPF, a substratum‐bound, neurite‐promoting factor
Authors: Adler Ruben 
Published: January 2005

AbstractThe responses of chick embryo retina neurons to the substratum‐bound, neurite‐promoting factor “PNPF” were studied using glia‐free, purified neuronal monolayers. Polyornithine‐coated dishes were exposed before cell seeding to either serum‐containing culture medium (PNPF(−) substratum) or to the same medium supplemented with 25% rat schwannoma conditioned medium, a source of PNPF (PNPF(+) substratum). The dishes were thoroughly rinsed before receiving a suspension of 8 day chick embryo neural retina cells in serum‐free medium.The presence of PNPF on the substratum determined a dramatic increase in the relative frequency of neurite‐bearing cells in the cultures. After 6 hours in vitro PNPF(+) cultures contained 45% neurite‐bearing cells, as compared with 5–7% on PNPN(−) substrata. At 72 hours those values increased to 60% on PNPF(+) and to 40% on PNPF(−) substrata. PNPF(+) cultures also showed longer and/or more highly branched neurites, resulting in the formation of complex neurite networks. Moreover, a cell type characterized by the presence of a very long neurite could be seen on PNPF(+) but not on PNPF(−) substrata.Six hour cultures were used to analyze in more detail the response of retinal neurons to PNPF. Addition of fetal calf serum to the medium determined a concentration‐dependent inhibition of neurite formation on PNPF(+) substrata. On the other hand, pretreatment of PNPF(+) substrata with concanavalin A also blocked the neurite‐promoting effect of the factor. This concentration‐dependent inhibitory effect of concanavalin A could be eliminated by the specific sugar α‐methyl‐D‐mannoside. Wheat germ agglutinin, another lectin known to react with PNPF, did not cause any reduction in the neurite‐promoting activity of this factor. Wheat germ agglutinin showed neurite‐promoting properties of its own in control experiments using PNPF(−) substrata.The results indicate that the target spectrum of PNPF is broader than it was originally thought. Together with other reports from the literature, they also support the perception of neurite development as a cellular activity subject to complex regulatory mechanisms.
Two components of conditioned medium increase neuritic outgrowth from rat spinal cord explants
Authors: Dribin Lori B. , Barrett John N. 
Published: January 2005

AbstractConditioned medium (CM) from muscle or fibroblast cultures dramatically increases the outgrowth of neurites from fetal rat spinal cord slices in vitro. We report here that there are two separable fractions in conditioned medium that cause this increase in neuritic outgrowth. One fraction, with a molecular weight of approximately 50,000 daltons, enhances neuritic outgrowth only when it is present in the culture medium so that the slices are directly exposed to it. The second component has a much larger molecular weight (above 300,000 daltons), and can enhance neuritic outgrowth by directly binding to the culture substrate on pretreatment. Only when these two fractions are combined by pretreating the substrate with the higher molecular weight fraction and then growing the slices in the lower molecular weight fraction is the full outgrowth promoting activity of whole conditioned medium reconstituted. These two components act synergistically to reproduce nearly the full outgrowth promoting activity of non‐fractionated, whole conditioned medium.
Antiserum to a new neuronal growth factor: Effects on neurite outgrowth
Authors: Coughlin Michael D. , Kessler John A. 
Published: January 2005

AbstractA new neuronal growth factor (CMF) isolated from mouse heart‐cell‐conditioned medium stimulates morphologic and biochemical development of mouse embryo sympathetic neurons [Coughlin et al, 1981]. Further analysis of CMF by chromatographic and electrophoretic procedures has shown that under nondissociating conditions, CMF activity is associated with very high molecular weight material. All biological activity eluted within the included volume of a Sepharose CL‐2B column in a molecular weight range corresponding to approximately 5 × 106 daltons. Similarly, electrophoresis showed no activity and very little protein entering 3% polyacrylamide gels, whereas both protein and activity migrated through 0.6% agarose‐1.2% acrylamide composite gels. To further characterize the biological effects of CMF on normal neuronal development, antibodies to CMF were employed. Rabbits immunized against CMF developed high titres of antibodies with activity specifically directed against CMF (anti‐CMF). Although anti‐CMF inhibited nerve growth factor (NGF)‐stimulated neurite outgrowth from the neonatal superior cervical ganglion, it did not inhibit the NGF‐stimulated increase in tyrosine hydroxylase activity. Moreover, ganglia incubated for 3 days in the presence of anti‐CMF were subsequently capable of producing neurites when washed and cultured in medium free of antiserum. Thus, anti‐CMF specifically blocked neurite extension without causing cell death or irreversible damage in ganglionic explants. Our observations suggest, therefore, that CMF or antigenically similar material is a requirement for neurite extension.
Developmental expression of rat brain mitogens for cultured astrocytes
Authors: Morrison Richard S. , Saneto Russell P. , de Vellis Jean 
Published: January 2005

AbstractExtracts prepared from prenatal, neonatal, and adult rat brain were examined for the presence of astrocyte mitogens. Extracts were characterized by molecular weight separation on Sephadex G‐100. Two major peaks of mitogenic activity, at 80K and 23K daltons, were identified in the adult brain extract. Extract prepared from adult tissue also possessed the lowest specific activity. Extract prepared from neonatal rat brain exhibited four general peaks of activity at approximately 80K, 45K, 23K, and 17K daltons. This extract possessed the highest specific activity. Extract prepared from prenatal rat brain contained six general peaks of activity with unique peaks at 67K, 14K, and less than 10K daltons. In addition, this extract possessed a specific activity intermediate between the adult and postnatal extracts. Differences were also noted among the extracts in their requirement for “permissive” factors found in serum necessary for mitogenic activity. The data have implications for the normal development of astrocytes, as well as for the pathological process of gliosis.
Effect of epidermal growth factor on membrane motility and cell locomotion in cultures of human clonal glioma cells
Authors: Westermark Bengt , Magnusson Annika , Heldin Carl‐Henrik 
Published: January 2005

AbstractTwo clones, designated Cl 2 and Cl 3, were established from the human malignant glioma line U‐343 MGa. The astrocytic origin of the cells was proven by the presence in virtually 100% of the cells of the astrocyte marker glial fibrillary acidic protein. The addition of 10 ng epidermal growth factor (EGF) per milliliter to Cl 2 and Cl 3 cells resulted in the rapid appearance of large cell surface ruffles, visualized by scanning electron microscopy. A time course study by phase contract microscopy showed that the maximal ruffling activity occurred 5 minutes after addition of EGF. Under basic culture conditions (Eagle's MEM, 10% fetal calf serum), Cl 2 and Cl 3 cells were essentially immobile and formed tightly packed, wel demarcated colonies. In the presence of 10 ng EGF per milliliter, no defined colonies were formed and the cells seemed to move around freely. The stimulatory effect of EGF on cell migration was confirmed by growing the cells on a deposit of colloidal gold; in the absence of EGF, the cells remained immobile whereas cells grown at 10 ng EGF per ml formed long phagokinetic tracks. The effect of EGF on membrane motility and cell locomotion occurred in the absence of any effect of EGF on growth rate; both clones multiplied at the same rate in the absence as in the presence of EGF. Binding experiments using 125I‐labeled EGF demonstrated a single class of high affinity receptors. The number of 180,000 receptors per cell was estimated in both clones. The finding that human glioma cells in culture require EGF for their migration raises the interesting possibility that tumor cells in vivo may respond in a similar fashion, and in that case require a growth factor for migration and for the expression of their infiltrative growth potential. Furthermore, the present findings strengthen the notion that glial cells should be recognized as targets for EGF.
Effects of kainic acid injection and cortical lesion on ornithine and aspartate aminotransferases in rat striatum
Authors: Wong P. T.‐H. , McGeer E. G. , McGeer P. L. 
Published: January 2005

AbstractThe effects of cortical lesions and intrastriatal kainic acid injections on various striatal enzyme activities were investigated. Ornithine aminotransferase decreased concomitantly with glutamate uptake in decorticated and chronic kainic acid‐treated rats. It was also decreased in acute kainic acid‐lesioned striatum where glutamate uptake was unaffected. Aspartate aminotransferase, however, decreased only after acute kainic acid treatment. Results for glutamate uptake, glutamate decarboxylase, and choline acetyltransferase were in agreement with previous findings. These results suggest that ornithine may act as a precursor for glutamate in nerve terminals, although the nonspecific localization does not allow ornithine aminotransferase to be a convenient biochemical marker. The decrease in aspartate aminotransferase is thought to be due to be widespread cell degeneration after acute kainic acid. Aspartate aminotransferase activities were also found to be reduced in the frontal cortex, caudate nucleus and putamen of Huntington's disease brains.
Effects of the taurine transport antagonist, guanidinoethane sulfonate, and β‐alanine on the morphology of rat retina
Authors: Pasantes‐Morales H. , Quesada O. , Cárabez A. , Huxtable R. J. 
Published: January 2005

AbstractNewborn rats treated for the first weeks of life with guanidinoethane sulfonate (GES), a blocker of taurine transport producing taurine depletion, showed a severe disruption of photoreceptor structure. Photoreceptor damage consisted of a marked reduction of the size of the photoreceptor layer, deformation of the outer segments, and a profound disorganization of the disc membranes. The GES‐induced degeneration pattern was very similar to that observed in cats fed a taurine‐deficient diet. Injection of β‐alanine, another antagonist of taurine transport, also produced a disruption of photoreceptor structure. These results confirm the requirement of taurine for maintaining photoreceptor structure in different species.
Dissociation of rapid eye movement (REM) sleep features: Possible implications for REM triggering mechanisms
Authors: Drucker‐Colín René , Dreyfus‐Cortés G. , Chávez L. , Aguilar R. , McGinty D. , Bowersox S. 
Published: January 2005

AbstractNeurophysiological and biochemical mechanisms regulating REM sleep episodes were studied in behaving cats with chronic electrodes. Push‐pull perfusion of the midbrain or pontine reticular formation (RF) by a protein synthesis inhibitor, chloramphenicol (CAP), reduced neuronal unit discharge, particularly discharge bursts, within the perfused area, and reduced the incidence of sustained REM periods. During transitions to “aborted” as compared to sustained REM episodes. RF unit discharge was reduced, under all conditions. In 72‐hour sleep deprived cats, systemic injections of both atropine (ATR) and CAP attenuated REM rebound, but with different patterns. CAP reduced REM episode frequency. ATR reduced REM duration. ATR also reduced PGO wave frequency. Combined CAP and ATR treatment produced additive REM depressant effects. These data suggest that cholinergic mechanisms regulate PGO activity and maintenance of REM episodes and that protein synthesis‐dependent mechanisms regulate RF unit discharge bursts, and REM triggering.
Evidence for a cyclic GMP mechanism in the mediation of hippocampal post‐tetanic potentiation
Authors: DeFrance J. F. , Stanley J. C. , Marchand J. E. , Divakaran P. , Clement‐Cormier Y. 
Published: January 2005

AbstractCorrelative electrophysiological and biochemical techniques were used to study hippocampal post‐tetanic potentiation in acutely prepared rabbits following stimulation of the medial septal region and contralateral hippocampal field CA3. The results indicate that calcium ions, guanosine‐3′:5′‐monophosphate, and phospho‐diesterase inhibitors selectively enhanced the duration of post‐tetanic potentiation. Potassium ions selectively enhanced tetanic potentiation. Adenosine‐3′:5′‐cyclic monophosphate suppressed both tetanic and post‐tetanic potentiation. The electrophysiological findings were supported by biochemical observations that guanosine‐3′:5′‐monophosphate levels show marked increases following tetanic stimulation of either the medial septal region or contralateral hippocampal field CA3 pathways.The data suggest that a calcium‐dependent process in the presence of a guanosine‐3′:5′‐monophosphate mechanism promotes periods of hippocampal pyramidal cell hyperexcitability. The mechanism by which the cyclic nucleotide alters potentiation does not appear to be coupled to a single receptor variety.
Influence of Venezuelan equine encephalomyelitis virus on catecholamine metabolism in mouse CNS: Early changes in turnover rates and content
Authors: Lima L. , Borges J. M. Díaz , Walder R. 
Published: January 2005

AbstractThe influence of two strains of Venezuelan equine encephalomyelitis virus on catecholamine metabolism in the central nervous system (CNS) of the mouse was studied by the intracranial inoculation of NMRT‐IVTC mice, 24 days old. Doses of 300 LD50 of the moderately virulent Pixuna strain and 104 LD50 of the non‐virulent TC‐83 strain were used. The animals were sacrificed 4, 7, 12, and 18 days after the inoculation, and the CNS contents of dopamine, norepinephrine, and adrenaline were determined by a radioenzymatic method. The turnover of these compounds was studied with the aid of the enzymatic inhibitors pargyline and alpha‐methyl tyrosine. With the Pixuna strain a decrease in the level and turnover of catecholamines was observed in all eight brain areas studied: cerebellum, pons‐medulla, hypothalamus, mesencephalon, striatum, olfactory bulb‐tuberculum, hippocampus, and cerebral cortex. In some regions the levels returned to normal in 12–18 days, but in the striaturn, mesencephalon, hypothalamus, and olfactory bulb‐tuberculum, recovery was slower and required at least 18 days after inoculation. The levels of catecholamines in the brain of mice inoculated with the nonvirulent TC‐83 strain were not modified, but there was a decrease in the turnover.
Commentary: Na+‐dependent and Na+‐independent binding of GABA in CNS subcellular particles – a search for GABA receptors
Authors: DeFeudis F. V. 
Published: January 2005

AbstractStudies of the Na+‐dependent and Na+‐independent binding of [3H] γ‐aminobutyric acid ([3H]GABA) and [3H]muscimol to central nervous system (CNS) subcellular preparations have been briefly reviewed and analyzed. Although some of the binding processes that have been detected in vitro, in the presence or absence of Na+, appear to represent GABA‐receptor interactions, further studies conducted with physiologic media and with highly purified membrane preparations are necessary in order to define the properties of those neuronal membrane receptors that mediate the in vivo actions of GABA.
The biosynthesis of p‐tyramine, m‐tyramine, and β‐phenylethylamine by rat striatal slices
Authors: Dyck L. E. , Yang C. R. , Boulton A. A. 
Published: January 2005

AbstractSlices of striatal tissue obtained from saline‐injected rats were incubated with 3H‐phenylalanine in the presence of pargyline. This resulted in the formation of 3H−m‐tyramine, 3H−p‐tyramine, and 3H‐phenylethylamine. Pretreatment of the rats with α‐methyl‐p‐tyrosine reduced the formation of 3H−m‐tyramine and 3H‐p‐tyramine, but enhanced the formation of 3H‐phenylethylamine.After incubation of striatal tissue obtained from saline‐injected rats with 3H‐ptyrosine, only 3H‐p‐tyramine was produced. In this case, α‐methyl‐p‐tyrosine pretreatment enhanced 3H‐p‐tyramine formation.Striatal slices incubated with 3H‐m‐tyramine or 3H‐p‐tyramine did not yield any significant quantity of 3H‐phenylethylamine; nor was 14C‐phenylethylamine converted to 14C‐m‐tyramine or 14C‐p‐tyramine. Pretreatment of the rats with the monoamine oxidase inhibitor pargyline did not appreciably affect these findings.After incubation with 3H‐dopamine very small quantities of 3H‐m‐tyramine and 3H‐p‐tyramine were formed, the ratio between them being 7:1.It is concluded that the major biosynthetic route for m‐tyramine formation in the rat straitum is by hydroxylation of phenylalanine, probably by tyrosine hydroxylase to m‐tyrosine, followed by decarboxylation, probably by L‐aromatic amino acid decarboxylase, to m‐tyramine. para‐Tyramine is formed by decarboxylation of p‐tyrosine, and phenylethylamine similarly by decarboxylation of phenylalanine.