bluuebunny/crossref_metadata_2025_split huggingface dataset:
Basic fibroblast growth factor and nerve growth factor administered in gel foam rescue medial septal neurons after fimbria fornix transection
Authors: Otto D. , Frotscher M. , Unsicker K. 
Published: January 2005

AbstractBasic fibroblast growth factor (bFGF) recently has been established as a survival‐ and transmitter‐promoting neurotrophic agent for embryonic neurons in vitro. Its local application to lesioned adult optic and sciatic nerves has been shown to rescue axotomized retinal and sensory neurons that otherwise die. Following transection of the fimbria fornix pathway connecting the medial septum (MS) to the hippocampus, MS neurons undergo severe cell death, which can be prevented partially by infusion of nerve growth factor (NGF). In the same lesion paradigm, we find that 87% of these neurons visualized by cresyl‐violet staining have disappeared by 4 weeks after unilateral fimbria fornix transection in adult rats. Implantation of gel foam soaked with 8 μg bFGF reduced neuron death to 68%. A similar rescue effect was seen with 0.3 μg NGF. NGF administered at 20 μg reduced cell losses to 54%. Thus, bFGF rescued 22% and NGF at 20 μg 38% of the neurons that otherwise would have died. Choline acetyltransferase immunocytochemistry revealed dramatic losses of cholinergic neurons on the lesioned, compared with the unlesioned, side. Cholinergic neuron death was clearly reduced by the bFGF and NGF treatments. Basic FGF, in contrast to NGF, did not prevent a reduction in size of surviving neuronal cell bodies. Considered in the context of FGF being present in brain and hippocampal neurons, our results suggest a possible role for FGF as a neurotrophic factor for CNS neurons in vivo.
Interaction of nerve growth factor with murine α‐macroglobulin
Authors: Koo P. H. , Stach R. W. 
Published: January 2005

AbstractThe murine nerve growth factor, when injected i.v. or, combined in vitro with plasma, was found largely associated with the mouse α‐macroglobulin (a homologue of human α2‐macroglobulin). The nerve growth factor α‐macroglobulin complex produced is sufficiently stable to resist separation by gel filtration in 1.0 M sodium chloride, polyacrylamide gel electrophoresis, and immunoprecipitation by antibodies against α‐macroglobulin. As determined by equilibrium binding studies and computer generated Scatchard analysis, α‐macroglobulin apparently possesses two types of binding sites with the apparent dissociation constants of 1.2 × 10−6 and 2.9 × 10−9 M, respectively, saturable by 3.7 and 0.03 moles of nerve growth factor. Hence, about one mole of nerve growth factor is bound to each of the four subunits of α‐macroglobulin. Nerve growth factor can be readily dissociated from α‐macroglobulin in sodium dodecyl sulfate gel electrophoresis in the absence of a reductant. Procedures that affect the proteinase‐binding or methylamine‐activities of α‐macroglobulin do not affect the binding of nerve growth factor, and the binding is unaffected by the presence of zinc ions or EDTA. Hence, nerve growth factor is noncovalently associated with α‐macroglobulin at a site separate from that of the proteinase‐, methylamine‐, and zinc‐binding sites of α‐macroglobulin. Mouse α‐macroglobulin can protect the nerve growth factor from inactivation by trypsin. Even in the presence of trypsin, α‐macroglobulin‐nerve growth factor complexes still can stimulate the neurite outgrowth by dorsal root ganglia of 9‐day‐old chicken embryos. Since α‐macroglobulin can specifically and noncovalently carry nerve growth factor, one important role of this α‐macroglobulin in the circulation and extracellular spaces may be to protect the nerve growth factor from proteinase inactivation.
Aged adrenal medullary tissue survives intraocular grafting, forms nerve fibers and responds to nerve growth factor
Authors: Strömberg I. , Ebendal T. 
Published: January 2005

AbstractAdrenal medullary tissue from aged (24 months old) and young adult (2 months old) rats was grafted to the anterior chamber of the eye of previously sympathectomized animals. Nerve growth factor (NGF) was administered by weekly bilateral intraocular injections. Five weeks postgrafting, irides were prepared as whole mounts and processed for Falck‐Hillarp histochemistry for visualization of catecholamines. NGF appeared to partially prevent the reduction in volume that both old and young grafts underwent. In the presence of NGF, an extensive, dense fiber network, closely resembling the normal adrenergic innervation, was formed in the host irides by grafts from aged donors. The area of outgrowth from aged transplants without NGF treatment was as large as with NGF treatment but less dense. The reinnervation of irides by NGF‐treated young adult grafts occupied a similar area as that seen with aged grafts, but the pattern of innervation was irregular, particularly close to the transplants. Transplants from young adult donors without NGF treatment generated a sparse, limited network of nerves in the irides. All grafts were tyrosine hydroxylase‐, adrenaline‐, and dopamine‐β‐hydroxylase‐immunoreactive in about the same proportion of cells, but the grafts from the young donors were smaller in size. We concluded that the ability of chromaffin cells to transform toward a neuronal phenotype, produce nerve fibers, and respond to exogenous NGF is maintained in aged adrenals.
Spontaneous and beta‐adrenergic receptor‐mediated taurine release from astroglial cells do not require extracellular calcium
Authors: Martin D. L. , Madelian V. , Shain W. 
Published: January 2005

AbstractAstroglial cells release taurine when stimulated by beta‐adrenergic agonists and other neuroactive agents. The Ca2+ ‐dependency of taurine release by an LRM55 astroglial cell line was investigated by removing Ca2+ from the perfusion medium and by using three inorganic and three organic Ca2+ ‐channel blockers (Mn2+, Co2+, Cd2+, verapamil, nifedipine, and diltiazem). Spontaneous release and release stimulated by the beta‐adrenergic agonist isoproterenol were not inhibited when cells were perfused with medium containing no added Ca2+ and 10 μM EGTA. Isoproterenol‐stimulated taurine release was not blocked when extracellular Ca2+ was completely replaced by Mn2+, Co2+, or Cd2+, nor was it blocked by verapamil, nifedipine, or diltiazem. In fact isoproterenol‐stimulated taurine release was increased by 50 μM diltiazem and when Ca2+ was replaced by Co2+. The rate of spontaneous release increased slowly and continually when Co2+ was substituted for Ca2+ or but was almost unaffected by substitution of Mn2+ or Cd2+. Application of diltiazem increased spontaneous release significantly, while verapamil and nifedipine appeared to cause small increases. These results indicate that entry of Ca2+ from the extracellular medium is not required for either receptor‐mediated or spontaneous taurine release from astroglial cells. Some other changes in the medium did strongly affect release. Both spontaneous and isoproterenol‐stimulated release were inhibited by elevated osmotic pressure, and spontaneous release was greatly increased when Ca2+ was completely removed without substituting another divalent cation. Spontaneous release increased when antagonistie metal ions were replaced with Ca2+ and when organic channel blockers were removed.
Sensory ganglia from tadpoles but not adult bullfrogs synthesize heat shock‐like proteins in vitro at non‐heat shock temperature
Authors: Hammerschlag R. , Maines S. , Ando M. 
Published: January 2005

AbstractLumbar dorsal root ganglia (DRG) from premetamorphic bullfrog tadpoles showed a selectively enhanced accumulation of two radiolabeled proteins when incubated in vitro at 22°C for longer than 1 hr. During the first hour in vitro or after in vivo labeling, these polypeptides–of 25 and 68 kD molecular mass and slightly acidic isoelectric point–were detected in the DRG only at relatively low levels. Accumulation of the 25 kD species increased in lumbar DRG from tadpoles of all metamorphic stages but waned at stage XXV (completion of metamorphosis) and was absent from DRG of adult bullfrogs. In contrast, increased levels of the 68 kD species were detected only at premetamorphic stages. Tail DRG from premetamorphic tadpoles did not increase their synthesis of either polypeptide in vitro, which is consistent with the above findings because sensory neurons in tail DRG, but not in lumbar DRG, are mature at this developmental stage. Although the molecular sizes of the two polypeptides led us initially to consider them as heat shock‐like proteins, only the 68 kD species was further increased (by approximately 100‐fold) when premetamorphic lumbar DRG were incubated at 37°C. The 25 kD species, which was the predominant protein induced at 22°C, showed no further increase in response to hyperthermia. The enhanced in vitro synthesis of these polypeptides at control temperature (22°C) is an example of cellular stress responses that may occur not as a consequence of elevated temperature or exogenous chemical agents, but as a result of transplantation‐associated trauma. This phenomenon also represents an example of a cellular stress response that is “outgrown” during development.
Muscarinic receptor subclasses in retinal cultures: Effect of corticosterone
Authors: Torelli S. , Sogos V. , Gremo F. 
Published: January 2005

AbstractWe have previously shown that exogenously administered corticosterone affects muscarinic receptor binding in the chick embryo retina. Analysis with the selective antagonist pirenzepine has shown that both muscarinic receptor subclasses M1 and M2 are present in treated retinas. On the contrary, only M2 is detectable in controls. Moreover, receptor affinity for agonists is modified by hormone treatment. Since these studies did not show whether or not the hormone directly influences retinal cells, a similar study was performed on retinal tissue cultures. Cells were treated at day 5 in vitro for 24 hr with 1.10−8 M corticosterone. Schatchard analysis of results obtained with 3H‐quinuclidinyl benzilate (3H‐QNB) binding showed no difference between treated and control cultures. However, displacement experiments demonstrated that both M1 and M2 were present in treated cultures, whereas controls had only M2. Also, receptor affinity for the agonist carbachol was modified, as already observed with in vivo studies. In addition, a new phenomenon was observed: treated cultures had a significantly higher number of cells. The possibility that the hormone can prevent cell death or stimulate cell mitosis is considered.
Carrier‐mediated Cl− transport in cultured mouse oligodendrocytes
Authors: Hoppe D. , Kettenmann H. 
Published: January 2005

AbstractWe studied the steady state and the regulation of intracellular Cl− activity (aCl−i) and the mechanisms of KCl uptake in cultured oligodendrocytes from mouse spinal cord using Cl−‐selective microelectrodes. The majority of oligodendrocytes actively accumulated Cl− above passive distribution (2–3 mM), few cells showed a passive Cl− distribution. To identify the carriers mediating Cl− uptake, oligodendrocytes were maintained in a solution with low extracellular Cl− concentration ([Cl−]0) which resulted in a rapid decrease in aCl−i. The recovery of aCl−i above its passive distribution in normal [Cl−]0 was blocked in the absence of Na+ or in the presence of furosemide and of bumetanide, which has been reported to inhibit Na+/K+/Cl− cotransport. We therefore conclude that Cl− uptake is primarily due to the activity of a Na+/K+/Cl− transport system. Cl− uptake above passive distribution was not affected in HCO3−‐free solution or in the presence of SITS and DIDS, indicating that Cl−/HCO3− exchange is not involved in Cl− uptake by oligodendrocytes. Elevation of [K+]0 induced an increase in aCl−i and, as shown earlier, intracellular K+ activity. This K+‐induced Cl− uptake was not blocked by bumetanide, furosemide, SITS, or DIDS, suggesting that under conditions of raised [K+]0 the combined uptake of K+ and Cl− is not mediated by a carrier, but can be explained by the entry through channels driven by Donnan forces.
Suppression of MYC by high expression of NMYC in human neuroblastoma cells
Authors: Breit S. , Schwab M. 
Published: January 2005

AbstractMembers of the MYC gene family, including MYC, NMYC, and LYMC, have been found amplified and expressed at high level in various human cancers. We have analysed the expression of two members of the MYC gene family, NMYC and MYC, in human and murine neuroblastoma cells. Whenever NMYC and MYC are co‐expressed, MYC expression predominates. Cells carrying high expression of NMYC as result of amplification lack MYC expression. The same is true for neuroblastoma cells in which expression of a single‐copy NMYC is upregulated or into which a vector forcing high expression of an exogenous NMYC had been introduced by transfection. Our studies indicate a regulatory interaction between MYC and NMYC in neuroblastoma cells.
Glutamate receptor agonists increase the expression of Fos, Fra, and AP‐1 DNA binding activity in the mammalian brain
Authors: Sonnenberg J. L. , Mitchelmore C. , Macgregor‐Leon P. F. , Hempstead J. , Morgan J. I. , Curran T. 
Published: January 2005

AbstractAdministration of convulsant doses of Metrazole (pentylenetetrazol) and picrotoxin, as well as maximal electroshock, results in a rapid but transient increase in c‐fos mRNA in mouse brain. Elevation of c‐fos mRNA is followed by the accumulation and subsequent disappearance of Fos, the protein encoded by c‐fos. In addition, immunoblots reveal the induction of two additional proteins that are antigenically related to Fos (Fra, Fos‐related antigens). Fos and the various Fra appear and disappear in a staggered manner over an 8 hour period, such that at longer times after stimulation the brain contains no Fos but relatively large amounts of Fra (the latter being designated here by their apparent molecular weights, Fra‐46K and Fra‐35K). Previous studies have established that Fos, as well as several Fra, contribute to transcription factor AP‐1 nucleoprotein complexes along with Jun, the product of the jun proto‐oncogene. The appearance in brain of Fos and Fra coincides with a protracted increase in total AP‐1 DNA binding activity, indicating that all the Fos‐like proteins can participate in AP‐1 complexes. Furthermore, the molecular composition of these complexes alters with time after stimulation. The induction of c‐fos by Metrazole is blocked or attenuated by known anticonvulsants such as diazepam and valproate as well as the N‐methyl‐D‐aspartate (NMDA) receptor antagonists, 2‐amino‐5‐phosphonovaleric acid (APV) and MK‐801. This suggests that fos induction might involve stimulation of a glutamate receptor. This conclusion was strengthened by the observations that two glutamate receptor agonists, kainic acid and NMDA, induced c‐fos expression. The induction of c‐fos by NMDA had a similar kinetic and pharmacological profile to that of Metrazole. Kainic acid, in contrast, caused a protracted induction of c‐fos not seen in any of the other paradigms. Therefore, it is likely that both the kainate and NMDA forms of the glutamate receptor may participate independently in the induction of c‐fos in the rodent nervous system.
Evolution of the neuron‐specific alternative splicing product of the c‐src proto‐oncogene
Authors: Raulf F. , Robertson S. M. , Schartl M. 
Published: January 2005

AbstractThe observation of a slower migrating form of pp60c‐src in neural tissue of chicken and mouse has recently been shown to be due to an alternative transcript form of the c‐src gene (Martinez et al.: Science 237:411–415, 1987; Levy et al.: Mol Cell Biol 7:4142–4145, 1987). An insertion of 18 basepairs between exons 3 and 4, presumed to be due to alternative splicing of a mini‐exon, gives rise to six amino acid residues not found in the non‐neuronal (termed fibroblastic) form of pp60c‐src.We have addressed the question of the evolutionary origin of the c‐src neuronal insert and its functional significance regarding neural‐specific expression of the c‐src gene. To this end we have investigated whether the c‐src gene of a lower vertebrate (the teleost fish Xiphophorus) gives rise to a neural‐specific transcript in an analogous manner. We could show that the fish c‐src gene does encode for a “fibroblastic” and a “neuronal” form of transcript and that the neuronal transcript does indeed arise by way of alternative splicing of a mini‐exon. The miniexon is also 18 basepairs long and we could demonstrate directly that this exon lies within the intron separating exons 3 and 4.For comparative purposes we have examined whether the fish c‐yes gene, the member of the src gene family most closely related to c‐src, also encodes a neural tissue‐specific transcript. No evidence for a second transcript form in brain was obtained. This result suggests that the mini‐exon arose within the c‐src gene lineage sometime between the src/yes gene duplication event and the divergence of the evolutionary lineage giving rise to the teleost fish. Published genomic sequence of src‐related genes in Drosophila and our own results with Hydra demonstrate no intron in these species at the analogous location, consistent with first appearance of this mini‐exon sometime between 550 and 400 million years ago.
Induction of c‐fos and TIS genes in cultured rat astrocytes by neurotransmitters
Authors: Arenander A. T. , de Vellis J. , Herschman H. R. 
Published: January 2005

AbstractThe interaction of neurotransmitters with their specific receptors initiates a cascade of intracellular biochemical events which lead to induction of specific genes. Included in this cascade is the rapid and transient induction of a family of primary early response genes we term TIS genes (Lim et al.: Oncogene 1:263–270, 1987). Expression of six TIS genes, including c‐fos, was examined in secondary cultures of rat neocortical astrocytes exposed to muscarinic and adrenergic agonists and antagonists to study the early genomic responses which accompany neurotransmitter‐induced alteration of glial morphology and physiology. Carbachol induced accumulation of mRNA for c‐fos and the other TIS genes. Carbachol‐meditated induction of TIS mRNA expression was sensitive to atropine blockade and was potentiated by lithium. Norepinephrine (NE), isoproterenol, or phenylephrine also induced TIS mRNA accumulation. In order to determine which second‐messenger pathways mediate NE induction of TIS gene expression, the influences of the beta(B) antagonist propranolol (PR), the alpha 1(A1) antagonist prazosin (PZ), and the alpha 2(A2) antagonist yohimbine (YB) were examined. The induction of TIS1 mRNA by NE was partially blocked by PR or PZ alone, and completely abolished by both antagonists in combination. YB had no effect on TIS1 mRNA expression. These results suggest that NE induces TIS1 mRNA through both B‐ and A1‐adrenergic, but not A2, pathways. The lack of effect of inhibitors of phospholipase A2 and cyclooxygenase suggests that the A1 component is mediated through a protein kinase C pathway. The induction of transient gene expression by neurotransmitters may mediate the secondary genomic responses and phenotypic changes occurring in astrocytes in response to alterations in neuronal neurotransmitter release.
Rapid growth of regenerating axons across the segments of sciatic nerve devoid of schwann cells
Authors: Sketelj J. , Bresjanac M. , Popović M. 
Published: January 2005

AbstractThe characteristic response of Schwann cells (SC) accompanies peripheral nerve injury and regeneration. To elucidate their role, the question of whether or not regenerating axons can elongate across the segments of a peripheral nerve devoid of SC was investigated. Rat sciatic nerve was crushed so that the continuity of SC basal laminae was not interrupted. A segment about 15 mm long distal to the crush was either repeatedly frozen/thawed to eliminate SC or scalded by moist heat which, in addition, denatured the proteins in the SC basal laminae, too. Both sensory and motor axons grew rapidly across the frozen/thawed segment of the nerve. Their rate of elongation was reduced by only 30% in comparison to control crushed nerves. SC were not present along the path of growing axons adhering tightly to the bare SC basal laminae. The rate of elongation of regenerating sensory and motor axons in scalded nerve segments was eight times lower than in control crushed nerves. SC were present in that part of the scalded region that had been invaded by the regenerating axons but no further distally.These results suggest that acellular basal laminae of SC provide very good, although not optimal, conditions for elongation of regenerating sensory and motor axons. If biochemical integrity of the basal lamina is destroyed, the regenerating axons must be accompanied or preceded by viable SC, and axon elongation rate is significantly reduced.
Release from live choroid plexus of apical fragments and electrophoretic characterization of their synthetic products
Authors: Gudeman D. M. , Brightman M. W. , Merisko E. M. , Merril C. R. 
Published: January 2005

AbstractProtein synthesis and secretion by the choroid plexus (CP) has been implicated as a major source of certain proteins in cerebrospinal fluid (CSF), such as transthyretin. The suggestion that proteins are elaborated from CP through apocrine secretion has been borne out by the presence of newly labeled proteins in apical protrusions from CP (Agnew et al.: Cell and Tissue Research 208:261–281, 1980a). When the protrusions (aposomes) separate from the cells, they continue to incorporate labeled amino acids (Gudeman et al.: Tissue and Cell 19:101–109, 1987). In the present work the formation of aposomes in live CP explants indicated that these spheroids were not the result of fixation. Aposomes were also identified within rat CSF by immunohistochemistry with monoclonal directed against aposomes as well as with anti‐transthyretin serum. The protein product of aposomes was characterized by 2‐dimensional SDS‐PAGE and compared to the protein products of whole CP tissue. Paradoxically, transthyretin, a heavily labeled protein in the tissue, was virtually undetected in the aposome synthetic profile. However, four other proteins were expressed in relatively equivalent amounts by the aposomes. The presence of mRNA in aposomes was detected with a poly dT probe, and the presence of actin was revealed by phalloidin staining of aposomes. These studies provide a more comprehensive definition of aposomes, but the functions of their secreted proteins remains to be determined.
Brain mitochondrial swelling induced by arachidonic acid and other long chain free fatty acids
Authors: Hillered L. , Chan P. H. 
Published: January 2005

AbstractPolyunsaturated fatty acids (PUFAs), arachidonic acid in particular, are well known, potent inducers of edema in the brain, while monounsaturated and saturated long chain fatty acids do not possess this quality. This investigation has compared the ability of some free fatty acids (FFAs), known to be released during cerebral ischemia, to induce brain mitochondrial swelling in vitro. The PUFAs tested, especially arachidonic acid (20:4), were more potent in causing swelling than saturated or monounsaturated ones, as measured by the decrease in light absorbance of the mitochondrial suspension. This finding is in line with the unique potency of 20:4 to induce brain edema. Incubation of brain mitochondria with 20:4 for 20 min caused a dose‐dependent swelling. ATP‐MgCl2 both prevented and reversed this swelling, while binding of the 20:4 by the addition of bovine serum albumin could only prevent but not reverse the swelling. The contraction of the swollen mitochondria appeared to be mediated by a mechanism dependent upon high‐energy phosphates, potentiated by MgCl2.The concentration of 20:4 required to induce swelling was about 20 times higher than the concentration required to induce inhibition of mitochondrial respiratory function (L Hillered and P H Chan: J Neurosci Res 19:94–100, 1988a). Morover, reversal of the swelling occurred without recovery of respiratory function. These results suggest that swelling is a phenomenon of minor importance as an indicator of brain mitochondrial dysfunction, at least when induced by 20:4 in vitro.