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Biomedical subjects

U Otten

Publications and source records attributed to U Otten.

At least 55 records · Page 3Linked to original sources
PubMed1995

Heterogeneity of human neuroblastoma cell lines in their proliferative responses to basic FGF, NGF, and EGF: correlation with expression of growth factors and growth factor receptors.

Growth factors can induce both proliferation or differentiation of neuroblastoma (NB) cells through interaction with specific receptors. Using two automated colorimetric assays for determinations of cell numbers, the present study demonstrates that a) different NB and neuroepithelioma cell lines show distinct responses, both qualitatively and quantitatively, to basic FGF (bFGF), NGF, and EGF; b) even closely related NB cell lines (e.g., SK-N-SH, SH-SY5Y, and SHEP) do not respond uniformly to these factors; c) responses of the two neuroepithelioma cell lines employed (SK-N-MC and CHP-100) differ, but match those of certain NB cell lines; and d) two growth factors, bFGF and EGF, may both stimulate or inhibit proliferation, depending on the cell line studied. Specifically, IMR-32, SK-N-SH, and SH-SY5Y showed a mitogenic response to each growth factor. Maximal proliferative responses ranged from 204-355% as compared to controls (100%). GICAN was stimulated by NGF (199%), and SK-N-MC and NMB by EGF (282 and 140%, respectively), but other factors were ineffective. CHP-100 and GIMEN were inhibited by bFGF. NGF and EGF were not effective on CHP-100 cells, while EGF caused an arrest of mitogenic activity in GIMEN cells, and NGF stimulated their proliferation. Cell lines SHEP and LAN1 did not respond to any factor. To begin to analyze putative relationships of growth factor responsiveness and growth factor/growth factor receptor expressions, IMR-32, GIMEN, and LAN1 cell lines were studied for the presence of bFGF, NGF, FGF receptors (R)-1 (flg) and FGFR-4, trk, and low-affinity NGF receptor (p75) mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗
PubMed1995

NGF: not just for neurons.

Nerve growth factor (NFF) is the prototypic member of a family of related neurotrophins (Nts). Although originally defined by its actions in the peripheral and central nervous systems, recent data indicate the presence of extensive interactions between NGF and the endocrine and immune systems steroid hormones are able to modulate the neurosomal expression NGF, while functional NGF receptors have been detected on cells of the immune system, and increased levels of NGF protein are found during the acute phase of diseases with a significant inflammatory component. These wider functions are likely to be of concern in any attempted therapeutic use of NGF.

Animals↗
PubMed1995

Nerve growth factor from the venom of the Chinese cobra Naja naja atra: purification and description of non-neuronal activities.

Nerve growth factor (NGF) was separated from crude Naja naja atra venom by using weak cation-exchange chromatography, followed by reversed-phase liquid chromatography. The yield of the purification was 0.2-0.5% (w/w). The mol. wt was determined to be 13,600 and the protein still induced the typical fibre outgrowth of cultured PC-12 cells in a concentration range of 5-10 ng/ml. Beside this neuronal effect we demonstrated non-neuronal effects of cobra venom NGF, such as induction of plasma extravasation and histamine release from whole blood cells. With human leucocyte preparations, including enriched basophils, there was an increase in C5a-induced histamine release, whereas NGF alone was inactive. Cobra NGF was one-tenth as potent as human recombinant NGF, with a half-maximal stimulation occurring at 10 ng/ml. Cobra NGF and human recombinant NGF showed a modulatory effect on histamine release comparable to the haematopoietic growth factor IL-3. Thus, the non-neuronal effects of cobra NGF may account for immunomodulatory activities during inflammatory events.

Animals↗
PubMed1995

Neurotrophin expression modulated by glucocorticoids and oestrogen in immortalized hippocampal neurons.

We have used reverse transcription followed by polymerase chain reaction amplification to investigate changes in expression of nerve growth factor (NGF) mRNA in immortalized hippocampal neurons after treatment with the glucocorticoids dexamethasone and corticosterone, the glucocorticoid antagonist RU38486, and the gonadal steroids progesterone and 17-beta oestradiol. We found that NGF mRNA levels rise after application of either dexamethasone or corticosterone, and that this rise is prevented by the antagonist. Thus, neurotrophin expression is modulated by the physiological glucocorticoid and is mediated by type II glucocorticoid receptors. Progesterone has no effect, while 17-beta oestradiol suppresses NGF mRNA in a postnatally-derived cell line but does not change levels in an embryonic line. An increase in neurotrophin expression is therefore not a general response to steroid hormone application, and may be a specific defence against the presence of metabolically endangering glucocorticoids.

Animals↗
PubMed1995

Acidic FGF induces NGF and its mRNA in the injured neocortex of adult animals.

Recently we reported that human recombinant acidic fibroblast growth factor (aFGF) is capable of preventing degeneration of nucleus basalis magnocellularis neurons in vivo and inducing growth of astrocytes in vitro. In the present study, the effects of aFGF on the concentration of nerve growth factor (NGF) and its messenger RNA were investigated in the rat cerebral cortex following unilateral cortical infarction. Lesioned animals exhibited a significant increase of NGF in the remaining cortex ipsilateral to the lesion. After combining cortical lesion with intracerebroventricular application of aFGF (12 micrograms/day for 7 days), we observed an 8-fold increase in the NGF concentration and a marked increase in the level of steady state NGF mRNA relative to controls ipsilaterally, and a less pronounced aFGF effect in the contralateral cerebral cortex. These results support the hypothesis that the neurotrophic effects previously shown for aFGF and basic FGF (bFGF) in neurotrophin-sensitive neurons is mediated by inducing increased production of NGF within the injured central nervous system (CNS) of adult animals.

Animals↗
PubMed1994

Identification of interleukin-6 (IL-6)-expressing neurons in the cerebellum and hippocampus of normal adult rats.

The cellular source of interleukin-6 (IL-6) in brain has not been identified. Using a sensitive, non-radioactive in situ hybridization technique, the cellular localization of IL-6 mRNA in different areas of the rat brain was analysed. Intense staining for IL-6 mRNA was found in Purkinje cells and hippocampal neurons. Our data support an essential role of IL-6 for cerebellar and hippocampal neuron differentiation and function.

Animals↗
PubMed1994

Expression of the cholecystokinin gene in rat hippocampal interneurons is independent of extrinsic input.

In the present study we have used slice cultures of hippocampus and in situ hybridization techniques in order to study the ability of hippocampal neurons to synthesize CCK mRNA in the absence of extrinsic afferents. Our results show that very similar types of hippocampal neurons express CCK mRNA in culture as in situ. We conclude that the expression of the CCK gene in hippocampal neurons is not dependent on extrinsic afferent input.

Animals↗
PubMed1994

Expression of functional trk tyrosine kinase receptors after T cell activation.

Increasing evidence indicates that nerve growth factor (NGF), in addition to its neurotrophic actions, exerts specific effects on cells of the immune system. This report show that the CD4-positive T cell line 9/6 expresses trk protooncogene, the signal transducing receptor unit for NGF, after TCR-mediated activation by Ag and APC. This receptor is of functional importance because interaction of NGF with Ag-stimulated 9/6 T cells induced the transcriptional activation of the c-fos gene, a hallmark of the biochemical response to NGF. Our findings that neither mitogen nor Ag stimulation induced the expression of the low affinity NGF receptor in 9/6 T cells indicate that trk alone is sufficient to mediate biologic activity of NGF in T lymphocytes.

Base Sequence↗
PubMed1994

Increased levels of nerve growth factor (NGF) protein and mRNA and reactive gliosis following kainic acid injection into the rat striatum.

After excitotoxic lesion of the rat striatum, the time courses of local nerve growth factor (NGF) and NGF mRNA contents were investigated using a sensitive immunoassay (ELISA) and reverse transcription coupled to polymerase chain reaction (RT/PCR). To investigate a possible correlation of increased NGF expression and excitotoxin-induced reactive gliosis, striata were also analysed by immunohistochemistry with glial markers. We found elevated striatal NGF protein after lesion over the whole observation period. NGF mRNA showed a biphasic increase 10 h and 10 days after lesion, the latter co-inciding with an increased astrogliosis. These results indicate that NGF accumulation after excitotoxin-induced neurodegeneration is partly due to local reactive astrocytes.

Animals↗
PubMed1994

Expression of interleukin-6 (IL-6) and interleukin-6 receptor (IL-6R) mRNAs in rat brain during postnatal development.

Using RT-PCR, the development profile of interleukin-6 (IL-6) and its receptor (IL-6R) mRNAs in rat brain was investigated. Our results indicate that IL-6 and IL-6R mRNAs are coexpressed and are developmentally regulated in a tissue-specific manner. Highest levels of both transcripts were detected in the adult hippocampus. Most pronounced developmental changes of IL-6 message levels were observed in the rat striatum increasing up to 8-fold. By contrast, in all other regions such as neocortex, hippocampus, cerebellum and pons/medulla oblongata only minor changes (2- to 3-fold) in IL-6 expression were seen. In most tissues IL-6 mRNA levels peaked at day 20. Marked induction of the receptor message levels was detected in the striatum, hippocampus and neocortex (8- to 10-fold) whereas no changes were observed in the cerebellum and the pons/medulla oblongata. The expression pattern of both genes in various brain areas during postnatal development strongly supports the concept of IL-6 as a candidate for a new neurotrophic factor.

Aging↗
PubMed1994

Postnatal ontogeny of the neurotrophin receptors trk and trkB mRNA in rat sensory and sympathetic ganglia.

Using reverse transcription followed by polymerase chain reaction, we examined the expression of mRNA for the tyrosine kinase receptors trk and trkB in rat sensory and sympathetic ganglia during postnatal development. While the levels of both trk and trkB mRNA in the dorsal root ganglia (DRG) decreased two-fold, they increased by seven and two times, respectively, in superior cervical ganglia. The developmentally regulated and tissue-specific expression of trk and trkB genes suggest that peripheral ganglia differ in their responsiveness to neurotrophins in neonatal and adult rats. We found that the temporal pattern of trk expression in DRG neurons correlates with the observed age-dependent ability of nerve growth factor to induce the biosynthesis of the neuropeptide substance P.

Animals↗
PubMed1993

Expression of nerve growth factor and nerve growth factor receptor tyrosine kinase Trk in activated CD4-positive T-cell clones.

Recent evidence suggests that nerve growth factor (NGF), in addition to its neurotrophic functions, acts as an immunomodulator mediating "cross-talk" between neuronal and immune cells, including T lymphocytes. We have analyzed murine CD4+ T-cell clones for their ability to express transcripts encoding NGF, low-affinity NGF receptor, and trk protooncogene, the signal-transducing receptor subunit for NGF. We show that two CD4+ T-helper (Th) clones, Th0-type clone 8/37 and Th2-type clone D10.G4.1, express NGF and Trk mRNA after appropriate activation with mitogen or with antigen and antigen-presenting cells. NGF and trk induction occurred to a similar extent and over a similar time course in activated 8/37 T cells, raising the possibility that NGF and trk genes are under coordinate control. NGF and NGF receptor expression does not seem to be a universal property of all activated CD4+ T cells, since Th1-type clone 9/9 did not express any of the transcripts after either stimulation. The absence of low-affinity NGF receptor mRNA in resting and activated T cells implies that the low-affinity NGF receptor is not involved in NGF signal transduction in CD4+ T cells. Our finding that activated CD4+ T-cell clones not only express Trk but also synthesize and release biologically active NGF implicates NGF as an autocrine and/or paracrine factor in the development and regulation of immune responses.

Animals↗
PubMed1993

Expression of low-affinity NGF receptor and trkB mRNA in human SH-SY5Y neuroblastoma cells.

We have used the human neuroblastoma cell line SH-SY5Y as a model system to investigate the expression and regulation of the receptors for brain-derived neurotrophic factor (BDNF), a member of the nerve growth factor (NGF) family of neurotrophins. We demonstrate that SH-SY5Y cells express transcripts encoding the low-affinity NGF receptor (LNGFR) and trkB, the signal transducing receptor unit for BDNF. Interaction of BDNF with SH-SY5Y cells increased the transcription of the c-fos gene, showing that these molecules encode functional BDNF receptors. Our findings that differentiating agents such as retinoids and cAMP analogs increased the expression of LNGFR, but decreased trkB mRNA levels, suggest that LNGFR and trkB have different roles during neuronal differentiation.

Base Sequence↗
PubMed1993

Influence of phenytoin on cytoskeletal organization and cell viability of immortalized mouse hippocampal neurons.

Phenytoin (PHT) is a commonly used anticonvulsant drug; several side effects have been described, including morphological changes in brain cortex and cerebellar neurons and teratogenic lesions in infants of epileptic mothers. Evidence of other authors indicate that PHT may exert its action through the modification of phosphorylation patterns of cytoskeletal polypeptides. We have studied the influence of the anticonvulsant drug phenytoin on immortalized mouse hippocampal neurons in culture. This was done by means of MTT-assays, immunocytochemical and immunoblot analyses, measurements of cell metabolism, measurements of the length of neuronal processes, and electron microscopy. A distinct and pronounced effect of PHT could be characterized with regard to the formation of neuronal processes, involving malfunction of an assembly-mechanism of cytoskeletal constituents. These accumulated within appendages (blebs) or cytoplasmic condensations, instead of forming normally organized processes. However, PHT did not interfere with bulk synthesis of cell proteins and specific cytoskeletal components.

Animals↗
PubMed1993

Expression of functional trk protooncogene in human monocytes.

There is increasing evidence that neurotrophins, including nerve growth factor (NGF), exert specific effects on cells of the immune system in addition to their neurotrophic actions. This report shows that human monocytes express the trk protooncogene, encoding the signal-transducing receptor unit for NGF. This receptor is functional, since interaction of NGF with monocytes triggered a respiratory burst, the major component of monocyte cytotoxic activity. During in vitro differentiation of human blood monocytes to macrophages trk expression decreased, suggesting a maturation-dependent trk expression decreased, suggesting a maturation-dependent trk regulation. Treatment of monocytes with Staphylococcus aureus Cowan I, a potent activator of monocytes, stimulated trk mRNA synthesis in a time-dependent way, implying a modulatory role for NGF in immune functions. The finding that dibutyryl cAMP elicited a time-dependent trk induction in monocytes as well as in phorbol ester-differentiated promonocytic U937 cells indicates that adenylate cyclase is involved in monocytic trk regulation. These results suggest that NGF, in addition to its neurotrophic function, is an immunoregulatory cytokine acting on monocytes.

Base Sequence↗
PubMed1993

Developmental neurotrophin expression in slice cultures of rat hippocampus.

Using reverse transcription in combination with the polymerase chain reaction, the developmental expression of neurotrophins in organotypic slice cultures of rat hippocampus was investigated. Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA levels after different time periods in vitro were compared with equivalent developmental stages in vivo. Our results show that neurotrophin expression occurs in hippocampal slice cultures with a similar time course as observed in the developing hippocampus in vivo. Thus, the development of neurotrophin expression in the hippocampus does not seem to be dependent on specific extrinsic afferents.

Afferent Pathways↗