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Thoenen H, Korsching S, Heumann R, Acheson A. Nerve growth factor. CIBA FOUNDATION SYMPOSIUM 2008; 116:113-28. [PMID: 3000703 DOI: 10.1002/9780470720974.ch8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In contrast to all other molecules which are labelled 'growth factor', NGF is not a mitogen. It is a neurotrophic molecule essential for the development and maintenance of function of specific populations of peripheral and possibly also central neurons. The availability of NGF in large quantities from exocrine glands (e.g. male mouse submandibular gland), where NGF does not play a neurotrophic role, has allowed the purification of NGF, the production of specific antibodies, the determination of its amino acid sequence and finally the molecular cloning of NGF leading to the elucidation of its precursor structure and its genomic organization. Comparison of the biological activities and the immunological properties of NGF isolated from different sources demonstrated that the active centre of the molecule has been highly conserved during evolution, whereas other parts of the molecule determining immunological properties have undergone considerable changes. After a survey of the essential biological actions of NGF, this paper concentrates on two actual questions of NGF research, namely the regulation of NGF synthesis in the target tissues of NGF-responsive neurons, and the molecular mechanism(s) of action of NGF on these neurons.
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2
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Abstract
The mammalian cerebral cortex requires the proper formation of exquisitely precise circuits to function correctly. These neuronal circuits are assembled during development by the formation of synaptic connections between hundreds of thousands of differentiating neurons. Although the development of the cerebral cortex has been well described anatomically, the cellular and molecular mechanisms that guide neuronal differentiation and formation of connections are just beginning to be understood. Moreover, despite evidence that coordinated patterns of activity underlie reorganization of brain circuits during critical periods of development, the molecular signals that translate activity into structural and functional changes in connections remain unknown. Recently, the neurotrophins have emerged as attractive candidates not only for regulating neuronal differentiation in the developing brain, but also for mediating activity-dependent synaptic plasticity. The neurotrophins meet many of the criteria required for molecular signals involved in neuronal differentiation and plasticity. They are present in the cerebral cortex during development and their expression is regulated by synaptic activity. In turn, the neurotrophins themselves strongly influence both short-term synaptic plasticity and long-term potentiation and depression. In addition to their functional effects, the neurotrophins also profoundly regulate the structural changes that underlie axonal and dendritic differentiation. Finally, the neurotrophins have been implicated in mediating synaptic competition required for activity-dependent plasticity during the critical period. This chapter presents and discusses the rapidly accumulating evidence that the neurotrophins are critical for neuronal differentiation and that they may be involved in activity-dependent synaptic refinement in the developing cerebral cortex.
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Affiliation(s)
- A Kimberley McAllister
- Center for Neuroscience, University of California, Davis, 1544 Newton Court, Davis, California 95616, USA
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Murer MG, Yan Q, Raisman-Vozari R. Brain-derived neurotrophic factor in the control human brain, and in Alzheimer's disease and Parkinson's disease. Prog Neurobiol 2001; 63:71-124. [PMID: 11040419 DOI: 10.1016/s0301-0082(00)00014-9] [Citation(s) in RCA: 624] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) is a small dimeric protein, structurally related to nerve growth factor, which is abundantly and widely expressed in the adult mammalian brain. BDNF has been found to promote survival of all major neuronal types affected in Alzheimer's disease and Parkinson's disease, like hippocampal and neocortical neurons, cholinergic septal and basal forebrain neurons, and nigral dopaminergic neurons. In this article, we summarize recent work on the molecular and cellular biology of BDNF, including current ideas about its intracellular trafficking, regulated synthesis and release, and actions at the synaptic level, which have considerably expanded our conception of BDNF actions in the central nervous system. But our primary aim is to review the literature regarding BDNF distribution in the human brain, and the modifications of BDNF expression which occur in the brain of individuals with Alzheimer's disease and Parkinson's disease. Our knowledge concerning BDNF actions on the neuronal populations affected in these pathological states is also reviewed, with an aim at understanding its pathogenic and pathophysiological relevance.
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Affiliation(s)
- M G Murer
- Departamento de Fisiologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay.
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Abstract
Despite considerable evidence that neuronal activity influences the organization and function of circuits in the developing and adult brain, the molecular signals that translate activity into structural and functional changes in connections remain largely obscure. This review discusses the evidence implicating neurotrophins as molecular mediators of synaptic and morphological plasticity. Neurotrophins are attractive candidates for these roles because they and their receptors are expressed in areas of the brain that undergo plasticity, activity can regulate their levels and secretion, and they regulate both synaptic transmission and neuronal growth. Although numerous experiments show demonstrable effects of neurotrophins on synaptic plasticity, the rules and mechanisms by which they exert their effects remain intriguingly elusive.
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Affiliation(s)
- A K McAllister
- Howard Hughes Medical Institute, Salk Institute, La Jolla, California 92037, USA.
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Synergistic increase in nerve growth factor secretion by cultured vascular smooth muscle cells treated with injury-related growth factors. J Neurosci Res 1997. [DOI: 10.1002/(sici)1097-4547(19970201)47:3<277::aid-jnr6>3.0.co;2-f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Zettler C, Bridges DC, Zhou XF, Rush RA. Detection of increased tissue concentrations of nerve growth factor with an improved extraction procedure. J Neurosci Res 1996; 46:581-94. [PMID: 8951670 DOI: 10.1002/(sici)1097-4547(19961201)46:5<581::aid-jnr7>3.0.co;2-f] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Nerve growth factor (NGF) is a protein essential for the survival and normal function of sympathetic neurons. Two-site immunoassays have been developed over the past decade in several laboratories and used to estimate its endogenous concentrations in a variety of effector tissues. However, levels appear restricted to a narrow range, display only a poor correlation with innervation density, and show obvious inter- and intralaboratory variations, the origins of which are unclear. This led us to examine alternative extraction procedures for NGF before quantification. In particular, we have found treatment of tissue extracts with high and low pH in the presence of detergent results in the detection of higher NGF concentrations in immunoassays using either polyclonal or commercially available monoclonal antibodies. These increases were tissue-specific (sciatic nerve, mesenteric arteries, and thoracic aorta > heart and brain > sympathetic ganglia > abdominal aorta) and as much as 10 times greater than the amounts detected by traditional procedures. The method should also prove useful for the assay of other members of the neurotrophin family when appropriate antibodies become available.
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Affiliation(s)
- C Zettler
- Department of Physiology, Flinders University of South Australia, Adelaide, Australia
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Heymach JV, Krüttgen A, Suter U, Shooter EM. The regulated secretion and vectorial targeting of neurotrophins in neuroendocrine and epithelial cells. J Biol Chem 1996; 271:25430-7. [PMID: 8810312 DOI: 10.1074/jbc.271.41.25430] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The varied roles that neurotrophins play in the development and activity-dependent plasticity of the nervous system presumably require that the sites and quantity of neurotrophin release be precisely regulated. As a step toward understanding how different neurotrophins are sorted and secreted by neurons, we expressed nerve growth factor (NGF), brain-derived neurotrophic factor, and neurotrophin-3 in cell lines used as models for neuronal protein sorting. All three neurotrophins were secreted by a regulated pathway in transfected AtT-20 and PC12 neuroendocrine cells, with a 3-6-fold increase in neurotrophin release in response to 8-bromo-cAMP or depolarization, respectively. To determine if the propeptide directs the intracellular sorting of mature NGF, we examined mutants in which regions spanning the propeptide were deleted. These mutants underwent regulated release in every case in which expression could be detected. Similarly, NGF sorting was not significantly altered by mutations which specifically abolished N-glycosylation or proteolytic processing sites within the NGF precursor. Finally, we found that all three neurotrophins were secreted 65-75% basolaterally by polarized Madin-Darby canine kidney epithelial cells. These findings suggest that the determinants of regulated neurotrophin secretion lie within the mature neurotrophin moiety and that NGF, brain-derived neurotrophic factor, and neurotrophin-3 are likely to be sorted similarly and released in a regulated manner by neurons.
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Affiliation(s)
- J V Heymach
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305-5401, USA
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Abstract
There is increasing evidence that neurotrophins (NTs) are involved in processes of neuronal plasticity besides their well-established actions in regulating the survival, differentiation, and maintenance of functions of specific populations of neurons. Nerve growth factor, brain-derived neurotrophic factor, NT-4/5, and corresponding antibodies dramatically modify the development of the visual cortex. Although the neuronal elements involved have not yet been identified, complementary studies of other systems have demonstrated that NT synthesis is rapidly regulated by neuronal activity and that NTs are released in an activity-dependent manner from neuronal dendrites. These data, together with the observation that NTs enhance transmitter release from neurons that express the corresponding signal-transducing Trk receptors, suggest a role for NTs as selective retrograde messengers that regulate synaptic efficacy.
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Affiliation(s)
- H Thoenen
- Department of Neurochemistry, Max Planck Institute for Psychiatry, Martinsried, Germany
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Matsushima S, Sakai Y, Hira Y. Sprouting of non-sympathetic myelinated and unmyelinated fibres in response to chronic sympathetic denervation in the pineal gland of the Chinese hamster, Cricetulus griseus. JOURNAL OF NEUROCYTOLOGY 1995; 24:519-31. [PMID: 7561960 DOI: 10.1007/bf01179977] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have examined the effects of chronic sympathetic denervation on non-sympathetic myelinated and unmyelinated fibres in the superficial pineal gland of the Chinese hamster (Cricetulus griseus), using LM, EM and immunohistochemistry. The results suggest that non-sympathetic, myelinated and unmyelinated fibres enter the superficial pineal gland at its distal portion by way of the nervi conarii, and that these fibres are immunoreactive for calcitonin gene-related peptide or substance P. Non-sympathetic, myelinated and unmyelinated fibres in the superficial pineal gland increased in number following chronic superior cervical ganglionectomy. The number of unmyelinated fibres in the nervi conarii also increased in ganglionectomized animals. Thus, the numerical increase of calcitonin gene-related peptide or substance P fibres found in the superficial pineal gland after long-term sympathectomy may be due to sprouting of these fibres. It is speculated that the growth of non-sympathetic, myelinated and unmyelinated fibres and myelination of the former fibres occurring after sympathectomy are caused by nerve growth factor-related mechanisms.
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Affiliation(s)
- S Matsushima
- Department of Anatomy, Asahikawa Medical College, Japan
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Blöchl A, Thoenen H. Characterization of nerve growth factor (NGF) release from hippocampal neurons: evidence for a constitutive and an unconventional sodium-dependent regulated pathway. Eur J Neurosci 1995; 7:1220-8. [PMID: 7582095 DOI: 10.1111/j.1460-9568.1995.tb01112.x] [Citation(s) in RCA: 274] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We investigated the mechanism of neuronal nerve growth factor (NGF) release with regard to the potential function of NGF as a mediator of neuronal plasticity in the CNS. The analysis was performed in hippocampal slices and in primary cultures of hippocampal neurons, transiently transfected with an NGF cDNA construct to increase the level of NGF expression. In both systems there was activity-dependent NGF release initiated by high potassium (KCl), veratridine, glutamate or carbachol. Replacement of 90% of sodium in the medium with N-methyl-glucamine strongly reduced this release. The KCl- and veratridine-initiated NGF release was suppressed by tetrodotoxin; release by glutamate was less sensitive to tetrodotoxin but was sodium-dependent. The glutamate effect could be inhibited by GYKI52644, an antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors, but not by MK-801, an antagonist of NMDA receptors. The activity-dependent release of NGF did not depend on extracellular Ca2+, but was sensitive to the intracellular Ca2+ chelator bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)-ester, and to depletion of intracellular calcium stores. Conversely, mobilization of Ca2+ from intracellular stores with caffeine and thapsigargin mimicked the effect of depolarization. Basal NGF release could be reduced by either temperature block (15 degrees C) or tetrodotoxin to approximately 50%. The combination of both treatments reduced NGF release to below the detection limit, suggesting that basal release has constitutive and regulated components, the latter presumably resulting from spontaneous activity of interconnected neurons.
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Affiliation(s)
- A Blöchl
- Max Planck Institute for Psychiatry, Department of Neurochemistry, Martinsried, Germany
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Lindholm D, Castrén E, Berzaghi M, Blöchl A, Thoenen H. Activity-dependent and hormonal regulation of neurotrophin mRNA levels in the brain--implications for neuronal plasticity. JOURNAL OF NEUROBIOLOGY 1994; 25:1362-72. [PMID: 7852991 DOI: 10.1002/neu.480251105] [Citation(s) in RCA: 226] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The neurotrophins exhibit neurotrophic effects on specific, partially overlapping populations of neurons both in the peripheral and the central nervous system (CNS). In the periphery, they are synthesized by a variety of nonneuronal cells, and their synthesis seems to be independent of the neuronal input. In contrast, in the CNS all neurotrophins are expressed under physiological conditions primarily by neurons. The production of NGF and BDNF is controlled by neuronal activity: up-regulation by glutamate and acetylcholine, down-regulation by gamma-aminobutyric acid. In contrast, NT-3 regulation is independent of neuronal activity, but it is up-regulated by thyroid hormones and BDNF. The latter observation suggests that NT-3 might be controlled indirectly by neuronal activity via BDNF. In peripheral nonneuronal tissues, glucocorticoid hormones down-regulate NGF mRNA levels both in vitro and in vivo. In contrast, in the CNS, neuronal production of NGF is enhanced by glucocorticoids. The rapid regulation of NGF and BDNF by subtle physiological stimuli together with the recent demonstration that the neurotrophins release neurotransmitters such as acetylcholine opens up interesting perspectives for the function of neurotrophins as mediators of neuronal plasticity.
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Affiliation(s)
- D Lindholm
- Department of Neurochemistry, Max Planck Institute for Psychiatry, Martinsried, Germany
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12
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Maness LM, Kastin AJ, Weber JT, Banks WA, Beckman BS, Zadina JE. The neurotrophins and their receptors: structure, function, and neuropathology. Neurosci Biobehav Rev 1994; 18:143-59. [PMID: 8170621 DOI: 10.1016/0149-7634(94)90043-4] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The neurotrophins are a family of polypeptides that promote differentiation and survival of select peripheral and central neurons. Nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, neurotrophin-4, and neurotrophin-5 are included in this group. In recent years, tremendous advances have been made in the study of these factors. This has stimulated our review of the field, characterizing the neurotrophins from initial isolation to molecular analysis. The review also discusses their synthesis, localization, and responsive tissues, in both the periphery and CNS. The complex receptor interactions of the neurotrophins are also analyzed, as are putative signal transduction mechanisms. Discussion of the observed and postulated involvement in neuropathological disorders leads to the conclusion that the neurotrophins are involved in the function and dysfunction of the nervous system.
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Affiliation(s)
- L M Maness
- Tulane University School of Medicine, New Orleans, LA 70146
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13
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Zhou XF, Williams R, Vahaviolos J, Zettler C, Rush RA. Ovalbumin-like immunoreactivity detected in chicken sensory neurons by antibodies to aldehyde-treated ovalbumin. ACTA ACUST UNITED AC 1993. [DOI: 10.1007/bf02388208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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14
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Meyer M, Matsuoka I, Wetmore C, Olson L, Thoenen H. Enhanced synthesis of brain-derived neurotrophic factor in the lesioned peripheral nerve: different mechanisms are responsible for the regulation of BDNF and NGF mRNA. J Biophys Biochem Cytol 1992; 119:45-54. [PMID: 1527172 PMCID: PMC2289627 DOI: 10.1083/jcb.119.1.45] [Citation(s) in RCA: 576] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are molecules which regulate the development and maintenance of specific functions in different populations of peripheral and central neurons, amongst them sensory neurons of neural crest and placode origin. Under physiological conditions NGF is synthesized by peripheral target tissues, whereas BDNF synthesis is highest in the CNS. This situation changes dramatically after lesion of peripheral nerves. As previously shown, there is a marked rapid increase in NGF mRNA in the nonneuronal cells of the damaged nerve. The prolonged elevation of NGF mRNA levels is related to the immigration of activated macrophages, interleukin-1 being the most essential mediator of this effect. Here we show that transsection of the rat sciatic nerve also leads to a very marked increase in BDNF mRNA, the final levels being even ten times higher than those of NGF mRNA. However, the time-course and spatial pattern of BDNF mRNA expression are distinctly different. There is a continuous slow increase of BDNF mRNA starting after day 3 post-lesion and reaching maximal levels 3-4 wk later. These distinct differences suggest different mechanisms of regulation of NGF and BDNF synthesis in non-neuronal cells of the nerve. This was substantiated by the demonstration of differential regulation of these mRNAs in organ culture of rat sciatic nerve and Schwann cell culture. Furthermore, using bioassays and specific antibodies we showed that cultured Schwann cells are a rich source of BDNF- and ciliary neurotrophic factor (CNTF)-like neurotrophic activity in addition to NGF. Antisera raised against a BDNF-peptide demonstrated BDNF-immunoreactivity in pure cultured Schwann cells, but not in fibroblasts derived from sciatic nerve.
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Affiliation(s)
- M Meyer
- Max-Planck Institute for Psychiatry, Department of Neurochemistry, Martinsried, Germany
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15
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García-Mauriño JE, Boya J, López-Muñoz F, Calvo JL. Immunohistochemical localization of nerve growth factor in the rat pineal gland. Brain Res 1992; 585:255-9. [PMID: 1380868 DOI: 10.1016/0006-8993(92)91214-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Sympathetic nerve fibers arising from the superior cervical ganglia are the main innervation of the rat pineal gland. Since most organs innervated by these ganglia contain nerve growth factor (NGF), the hypothetical existence of NGF in the pineal gland was investigated. The peroxidase anti-peroxidase technique was applied for the immunohistochemical demonstration of NGF using a polyclonal antiserum on Bouin-fixed, paraffin-embedded pineal glands from adult, young and 6-hydroxydopamine (6-OHDA)-treated rats. Few immunopositive cells were observed in the adult pineal gland. A more conspicuous population of immunoreactive cells was noted in young animals (20-45 days old), especially in those chemically denervated with 6-OHDA. NGF immunoreactive cells displayed a stellate shape resembling the interstitial or glial cells previously described in the rat pineal gland. Since NGF plays a trophic effect on sympathetic neurons during development and adulthood, we postulate that its presence in the pineal gland may exert a trophic role on its sympathetic innervation.
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Affiliation(s)
- J E García-Mauriño
- Department of Histology, Faculty of Medicine, University Complutense, Madrid, Spain
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16
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Tripathi BJ, Tripathi RC, Livingston AM, Borisuth NS. The role of growth factors in the embryogenesis and differentiation of the eye. THE AMERICAN JOURNAL OF ANATOMY 1991; 192:442-71. [PMID: 1781453 DOI: 10.1002/aja.1001920411] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The vertebrate eye is composed of a variety of tissues that, embryonically, have their derivation from surface ectoderm, neural ectoderm, neural crest, and mesodermal mesenchyme. During development, these different types of cells are subjected to complex processes of induction and suppressive interactions that bring about their final differentiation and arrangement in the fully formed eye. With the changing concept of ocular development, we present a new perspective on the control of morphogenesis at the cellular and molecular levels by growth factors that include fibroblast growth factors, epidermal growth factor, nerve growth factor, platelet-derived growth factor, transforming growth factors, mesodermal growth factors, transferrin, tumor necrosis factor, neuronotrophic factors, angiogenic factors, and antiangiogenic factors. Growth factors, especially transforming growth factor-beta, have a crucial role in directing the migration and developmental patterns of the cranial neural-crest cells that contribute extensively to the structures of the eye. Some growth factors also exert an effect on the developing ocular tissues by influencing the synthesis and degradation of the extracellular matrix. The mRNAs for the growth factors that are involved in the earliest aspects of the growth and differentiation of the fertilized egg are supplied from maternal sources until embryonic tissues are able to synthesize them. Subsequently, the developing eye tissues are exposed to both endogenous and exogenous growth factors that are derived from nonocular tissues as well as from embryonic fluids and the systemic circulation. The early interaction between the surface head ectoderm and the underlying chordamesoderm confers a lens-forming bias on the ectoderm; later, the optic vesicle elicits the final phase of determination and enhances differentiation by the lens. After the blood-ocular barrier is established, the internal milieu of the eye is controlled by the interactions among the intraocular tissues; only those growth factors that selectively cross the barrier or that are synthesized by the ocular tissues can influence further development and differentiation of the cells. An understanding of the tissue interactions that are regulated by growth factors could clarify the precise mechanism of normal and abnormal ocular development.
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Affiliation(s)
- B J Tripathi
- Department of Ophthalmology and Visual Science, University of Chicago, Illinois
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17
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Zafra F, Castrén E, Thoenen H, Lindholm D. Interplay between glutamate and gamma-aminobutyric acid transmitter systems in the physiological regulation of brain-derived neurotrophic factor and nerve growth factor synthesis in hippocampal neurons. Proc Natl Acad Sci U S A 1991; 88:10037-41. [PMID: 1658793 PMCID: PMC52862 DOI: 10.1073/pnas.88.22.10037] [Citation(s) in RCA: 407] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In the central nervous system brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are predominantly located in neurons. Here we demonstrate that the balance between the activity of the glutamatergic and gamma-aminobutyric acid (GABA)ergic systems controls the physiological levels of BDNF and NGF mRNAs in hippocampal neurons in vitro and in vivo. The blockade of the glutamate receptors and/or stimulation of the GABAergic system reduces BDNF and NGF mRNAs in hippocampus and NGF protein in hippocampus and septum. The reduction of NGF in the septum reflects the diminished availability of NGF in the projection field of NGF-dependent septal cholinergic neurons. These neurons do not synthesize NGF themselves but accumulate it by retrograde axonal transport. The refined and rapid regulation of BDNF and NGF synthesis by the glutamate and GABA transmitter systems suggests that BDNF and NGF might be involved in activity-dependent synaptic plasticity.
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Affiliation(s)
- F Zafra
- Department of Neurochemistry, Max-Planck-Institute for Psychiatry, Planegg-Martinsried, Federal Republic of Germany
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18
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Rawdon BB. Extension of sympathetic neurites in vitro towards explants of embryonic and neonatal mouse heart and stomach: ontogeny of neuronotrophic factors. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1991; 59:49-58. [PMID: 2040079 DOI: 10.1016/0165-3806(91)90028-h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In order to establish when target organs first produce neuronotrophic factors, extension of neurites in vitro from sympathetic ganglia (superior cervical and coeliac) of 1-day neonatal mice towards explants of 10-, 11-, 14- and 17-day embryonic and 1-day neonatal atrium and stomach was examined in co-cultures. Longer neurites extended from ganglia towards, than away from, atrial targets at all stages examined, and was most marked towards 17-day embryonic and neonatal explants. Treatment of atrial co-cultures with antiserum to nerve growth factor (NGF) almost totally blocked preferential neurite outgrowth. Directional growth of neurites towards stomach explants in co-cultures was not as pronounced as that towards atrium; extension of neurites was most marked when stomach was provided by 11-, 14- and 17-day embryos. Such outgrowth was only partially blocked by antiserum to NGF, significant preferential extension of neurites towards stomach persisting in the presence of the antiserum. These results indicate that atrium and stomach produce neuronotrophic factors from the earliest ages studied; the evidence indicates that in the case of atrium, NGF predominates but that stomach produces NGF as well as another factor immunologically distinct from NGF. It is of interest that both types of target explanted before they receive sympathetic innervation show evidence of producing NGF in culture.
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Affiliation(s)
- B B Rawdon
- Department of Anatomy and Cell Biology, Medical School, University of Cape Town, Observatory, South Africa
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19
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Tripathi RC, Fekrat S, Tripathi BJ, Borisuth NSC. Role of growth factors in the uveal tract of the eye as targeted to the development of new drugs. Drug Dev Res 1991. [DOI: 10.1002/ddr.430230102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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20
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Davies AM. Nerve growth factor synthesis and nerve growth factor receptor expression in neural development. INTERNATIONAL REVIEW OF CYTOLOGY 1991; 128:109-38. [PMID: 1655670 DOI: 10.1016/s0074-7696(08)60498-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A M Davies
- Department of Anatomy, St. George's Hospital Medical School, London, England
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Zafra F, Hengerer B, Leibrock J, Thoenen H, Lindholm D. Activity dependent regulation of BDNF and NGF mRNAs in the rat hippocampus is mediated by non-NMDA glutamate receptors. EMBO J 1990; 9:3545-50. [PMID: 2170117 PMCID: PMC552104 DOI: 10.1002/j.1460-2075.1990.tb07564.x] [Citation(s) in RCA: 652] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The mRNAs of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) exhibit a similar, though not identical, regional and cellular distribution in the rodent brain. In situ hybridization experiments have shown that BDNF, like NGF, is predominantly expressed by neurons. The neuronal localization of the mRNAs of these two neurotrophic molecules raised the question as to whether neuronal activity might be involved in the regulation of their synthesis. After we had demonstrated that depolarization with high potassium (50 mM) resulted in an increase in the levels of both BDNF and NGF mRNAs in cultures of hippocampal neurons, we investigated the effect of a large number of transmitter substances. Kainic acid, a glutamate receptor agonist, was by far the most effective in increasing BDNF and NGF mRNA levels in the neurons, but neither N-methyl-D-aspartic acid (NMDA) nor inhibitors of the NMDA glutamate receptors had any effect. However, the kainic acid mediated increase was blocked by antagonists of non-NMDA receptors. Kainic acid also elevated levels of BDNF and NGF mRNAs in rat hippocampus and cortex in vivo. These results suggest that the synthesis of these two neurotrophic factors in the brain is regulated by neuronal activity via non-NMDA glutamate receptors.
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Affiliation(s)
- F Zafra
- Max-Planck-Institute for Psychiatry, Department of Neurochemistry, Planegg-Martinsried, FRG
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Spranger M, Lindholm D, Bandtlow C, Heumann R, Gnahn H, Näher-Noé M, Thoenen H. Regulation of Nerve Growth Factor (NGF) Synthesis in the Rat Central Nervous System: Comparison between the Effects of Interleukin-1 and Various Growth Factors in Astrocyte Cultures and in vivo. Eur J Neurosci 1990; 2:69-76. [PMID: 12106104 DOI: 10.1111/j.1460-9568.1990.tb00382.x] [Citation(s) in RCA: 327] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to obtain information on the physiological regulation of NGF-synthesis in the central nervous system (CNS) we investigated the effects of a series of growth factors (known to be present in the CNS) in cultures of purified rat astrocytes and compared these effects with those observed after intraventricular injection of the same molecules. After preliminary experiments had shown that 10% fetal calf serum (FCS) produced a marked increase in NGF-mRNA levels in astrocytes (but neither in microglia nor oligodendrocytes) as demonstrated by Northern blot analysis and in situ hybridization the experiments were performed at low (0.5%) FCS concentrations. Supramaximal concentrations of IL-1 and various growth factors caused a 5- to 7-fold increase in NGF-mRNA after 6 h. By 24 h the NGF-mRNA levels approached control values again, most probably due to inactivation of the added factors since after readdition after 24 h the response was about the same as the initial one. Norepinephrine and 8-bromo-cAMP did not change NGF-mRNA levels. The growth factor-mediated changes in NGF-mRNA levels in astrocyte cultures were not consistently reflected by the changes observed after intraventricular injection. IL-1 produced by far the largest increase in hippocampal NGF-mRNA after intraventricular injection. This large response to IL-1 could result from a positive feedback mechanism, since IL-1beta injection not only increases NGF-mRNA but also IL-1beta-mRNA in the hippocampus. The understanding of the physiological regulation of NGF synthesis in the CNS is the basis for a rational approach to its pharmacological modification. This, in turn, is an attractive alternative to the (long-term) infusion of NGF or the transplantation of NGF-secreting cells with the goal of providing trophic support to the cholinergic neurons of the basal forebrain nuclei. These neurons are consistently affected in the early stages of Alzheimer's disease, their impaired function being essentially responsible for the cognitive deficits.
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Affiliation(s)
- Matthias Spranger
- Max-Planck-Institute for Psychiatry, Department of Neurochemistry, Am Klopferspitz, D-8033 Martinsried
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23
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Blottner D, Unsicker K. Spatial and temporal patterns of neurotrophic activities in rat adrenal medulla and cortex. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1989; 48:243-53. [PMID: 2776296 DOI: 10.1016/0165-3806(89)90079-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have studied the spatial distribution and temporal pattern of expression of neurotrophic factor (NTF) activity present in the rat adrenal gland. Tissue extracts of the densely innervated medulla and sparsely innervated cortex from adult and various developmental stages were assayed for their ability to promote the in vitro survival of embryonic chick ciliary (CG), dorsal root ganglia (DRG) and ventral spinal cord (SC) neurons. NTF activity was found in medulla but not in cortex extracts. NTF activity became first detectable at postnatal day (P) 12. At this developmental stage the cholinergic adrenomedullary innervation becomes functional. Specific activity successively increased in medulla extracts from P16 to P30 as revealed by the CG-assay. No further changes occurred during adulthood. In contrast, activity addressing SC neurons present in P16 and P30 medulla extracts could not be detected in adult stages P90 or P120. In DRG-assays, NTF activity could not be blocked by the addition of anti-NGF antibodies to medulla extracts. The activity was sensitive to heat and protease treatment suggesting its proteinaceous nature. At high concentrations cortex extracts had neurotoxic effects that were also seen when 10 microM of dexamethasone were added to saturated amounts of medulla extract. However, gel filtration of cortex material to remove low molecular components including corticosteroid hormones failed to reveal any NTF activity in these preparations. Adrenal NTF activity therefore appears to be restricted to the densely innervated medullary tissue. Moreover, our results also suggest a distinct temporal pattern of NTF activity in the adrenal gland.
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Affiliation(s)
- D Blottner
- Department of Anatomy and Cell Biology, Philipps-University, Marburg, F.R.G
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24
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Clegg DO, Large TH, Bodary SC, Reichardt LF. Regulation of nerve growth factor mRNA levels in developing rat heart ventricle is not altered by sympathectomy. Dev Biol 1989; 134:30-7. [PMID: 2471662 DOI: 10.1016/0012-1606(89)90075-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The survival of sympathetic and sensory neurons is known to be controlled by nerve growth factor (NGF) supplied by the targets of innervation, yet little is known about how target NGF synthesis is regulated. We have investigated the pattern of NGF mRNA expression in developing rat heart ventricle using a sensitive RNA blotting procedure. We find that the concentration of NGF mRNA increases steadily from Embryonic Day 17 to peak levels at 10-14 days postnatal and then declines about twofold and stabilizes at the level found in adults. The rise in NGF mRNA concentration correlates with the arrival and differentiation of sympathetic nerve terminals in the heart and the cessation of sympathetic cell death. To assess the role of innervating sympathetic neurons in regulating NGF mRNA expression, neonatal rats were sympathectomized by treatment with 6-hydroxydopamine and heart ventricles were assayed for NGF message. Although this treatment reduced ventricle norepinephrine content by 82%, no significant change in NGF mRNA concentration was observed. These results suggest that the developmental program of NGF mRNA production in the heart is not influenced by innervating sympathetic neurons.
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Affiliation(s)
- D O Clegg
- Howard Hughes Medical Institute Neuroscience Research Unit, University of California, San Francisco 94143
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25
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Affiliation(s)
- Y A Barde
- Max-Planck Institute for Psychiatry, Department of Neurochemistry, Martinsried Munich, Federal Republic of Germany
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26
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Houlgatte R, Wion D, Brachet P. Levels of nerve growth factor secreted by rat primary fibroblasts and iris transplants are influenced by serum and glucocorticoids. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1989; 47:171-9. [PMID: 2743556 DOI: 10.1016/0165-3806(89)90173-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Previous work performed with mouse fibroblast-like L cells has shown that the level of expression of NGF gene is modulated in these transformed cells by the composition of the growth medium. Glucocorticoids were found to exert a down-regulation on NGF production, while serum stimulated the synthesis of the factor. The contrasting effects of serum and dexamethasone were further investigated in cultures of primary rat fibroblasts or in iris transplants. ELISA assays of NGF released by fibroblasts or by transplanted irides showed that both experimental systems responded to dexamethasone by a 4-5-fold decrease of the amounts of secreted factor. Half-maximal effect took place at a concentration of 3-5 X 10(-9) M, a value close to the dissociation constant of the glucocorticoid receptor in fibroblasts. The glucocorticoid did not influence the secretion of macromolecules. Assays of NGF mRNA performed at a concentration of 10(-7) M dexamethasone indicated that the steroid decreased the pool of NGF transcripts in either experimental systems. In contrast to dexamethasone, serum induced a 4-fold enhancement of the amounts of factor secreted by fibroblasts. This effect was reproduced with serum that was previously heat-treated at mild acidic pH, or with a macromolecular fraction of this heat-treated serum which contains an effector promoting NGF synthesis in L cells. The fact that promotion of NGF synthesis takes place in primary cells raises the possibility that this process may also occur in vivo, for instance following disruption of vasculature, as a part of a wound mechanism. Data collected with iris transplants provide some support to this interpretation.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R Houlgatte
- INSERM U298, Centre Hospitalier Régional Universitaire, Angers, France
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27
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Naftel JP. Reduction in sympathetic neuronotrophic activity in the pulp of the cat canine tooth after denervation. Arch Oral Biol 1989; 34:453-8. [PMID: 2597037 DOI: 10.1016/0003-9969(89)90124-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Most of the nerve fibres supplying the mandibular canine on one side were interrupted by sectioning the inferior alveolar nerve (IAN) and, after 1 week, the trophic activity in each mandibular canine pulp was assessed in an in vitro assay using sympathetic neurones from 11-day chick embryos as test cells. In eight of nine animals tested, neuronotrophic activity in the denervated pulp was markedly lower than in the contralateral control pulp. Antiserum to mouse nerve growth factor had no effect on the trophic activity in either control or denervated pulps. Thus, the pulp differs from other peripheral tissues, which undergo increases in neuronotrophic activity after denervation. The basis of this difference may be the high innervation density of the pulp. The IAN distal to the site of nerve transection also had reduced survival-promoting activity.
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Affiliation(s)
- J P Naftel
- Department of Anatomy, University of Mississippi Medical Center, Jackson 39216
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28
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Lahtinen T, Soinila S, Lakshmanan J. Biological demonstration of nerve growth factor in the rat pituitary gland. Neuroscience 1989; 30:165-70. [PMID: 2747910 DOI: 10.1016/0306-4522(89)90362-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Explants of anterior, intermediate and posterior pituitary lobes of rats at various ages evoked an intense nerve fibre outgrowth when co-cultured with neonatal sympathetic superior cervical ganglia in a collagen gel medium. Freezing and thawing of pituitary lobes, prior to culture, did not abolish their growth-promoting effect. Since the addition of antiserum to nerve growth factor in the culture medium inhibited totally the stimulative action of both fresh and frozen pituitary explants it is suggested that the stimulation is mediated by nerve growth factor or an immunologically related molecule. Based on the present results it is concluded that nerve growth factor is synthesized by both the anterior, intermediate and posterior lobes throughout the postnatal period, as well as in adult rats. The function of nerve growth factor in the pituitary gland is discussed.
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Affiliation(s)
- T Lahtinen
- Department of Anatomy, University of Helsinki, Finland
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29
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Hellweg R, Bandtlow CE, Heumann R, Korsching S. Nerve growth factor synthesis in cultured rat iris: modulation by endogenous transmitter substances. Exp Cell Res 1988; 179:18-30. [PMID: 2844567 DOI: 10.1016/0014-4827(88)90344-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Organ cultures of rat iris show a characteristic change in the levels of both nerve growth factor (NGF) and its mRNA: a rapid but transient initial increase is followed by a smaller but persistently elevated NGF synthesis. This time course may be influenced by release of a factor(s) from degenerating nerve terminals and/or by the lack of some factor(s) repressing NGF synthesis in vivo. We therefore analyzed the influence of biogenic amine transmitter substances and putative neuropeptides on this elevation of NGF synthesis in cultured iris. The marked increase of NGF synthesis seen initially in culture was not completely mimicked by any of the substances tested. A specific increase in NGF production up to 150% of control was observed only with cGMP. We also obtained some evidence that reaction to trauma following the culture procedure could enhance NGF production: cutting of irides into small pieces increased NGF production in culture up to 250% of control and, vice versa, treatment with 1 microM dexamethasone decreased NGF production to about 60% of control. However, the sympathetic neurotransmitter norepinephrine (NE) decreased both NGF and its mRNA levels specifically in a dose-dependent manner (0.01-1 mM) to a minimum of about 25% of control. In situ hybridization with mRNA(NGF)-specific probes showed that in cultures of dissociated iris cells all cells were capable of expressing mRNA(NGF), but that 0.1 mM NE preferentially decreased expression of mRNA(NGF) in smooth muscle cells. Thus, our results indicate that the sympathetic transmitter NE is capable of downregulating NGF synthesis in the target cells of sympathetic neurons.
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Affiliation(s)
- R Hellweg
- Max-Planck-Institute for Psychiatry, Department of Neurochemistry, Planegg-Martinsried, Federal Republic of Germany
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30
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Processing and secretion of nerve growth factor: expression in mammalian cells with a vaccinia virus vector. Mol Cell Biol 1988. [PMID: 3405211 DOI: 10.1128/mcb.8.6.2456] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
To study posttranslational mechanisms for the control of nerve growth factor (NGF), we used a recombinant vaccinia virus vector to independently express the two major NGF transcripts in a variety of mammalian cell lines. The two major transcripts contain NGF (12.5 kilodaltons [kDa]) at the C-terminus and differ by alternative splicing of an N-terminal exon, so that the large precursor (34 kDa) had 67 amino acids upstream of an internal signal peptide and the smaller precursor (27 kDa) had this signal peptide at its N-terminus. In L929 cells, expression of either NGF transcript with the vaccinia virus vector gave rise to an apparently identical intracellular 35-kDa glycosylated precursor formed by cleavage of the primary gene product after the signal peptide. These cells also secreted biologically active NGF. To determine whether NGF processing is restricted by cell type, we infected a variety of mammalian cell lines with both recombinant viruses; all accumulated the same 35-kDa precursor and secreted NGF. Thus, many types of cells have the machinery to process and secrete NGF. However, NGF accumulated intracellularly (presumably in secretory granules) in cells with a regulated pathway of secretion (e.g., AtT-20 and HIT cells). In these cells, a membrane-permeable cyclic AMP analog, 8-bromo-cyclic AMP, stimulated NGF secretion. This suggests a mechanism for the regulation of NGF levels in which specific secretagogues, e.g., neurotransmitters, control NGF secretion.
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31
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Edwards RH, Selby MJ, Mobley WC, Weinrich SL, Hruby DE, Rutter WJ. Processing and secretion of nerve growth factor: expression in mammalian cells with a vaccinia virus vector. Mol Cell Biol 1988; 8:2456-64. [PMID: 3405211 PMCID: PMC363445 DOI: 10.1128/mcb.8.6.2456-2464.1988] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
To study posttranslational mechanisms for the control of nerve growth factor (NGF), we used a recombinant vaccinia virus vector to independently express the two major NGF transcripts in a variety of mammalian cell lines. The two major transcripts contain NGF (12.5 kilodaltons [kDa]) at the C-terminus and differ by alternative splicing of an N-terminal exon, so that the large precursor (34 kDa) had 67 amino acids upstream of an internal signal peptide and the smaller precursor (27 kDa) had this signal peptide at its N-terminus. In L929 cells, expression of either NGF transcript with the vaccinia virus vector gave rise to an apparently identical intracellular 35-kDa glycosylated precursor formed by cleavage of the primary gene product after the signal peptide. These cells also secreted biologically active NGF. To determine whether NGF processing is restricted by cell type, we infected a variety of mammalian cell lines with both recombinant viruses; all accumulated the same 35-kDa precursor and secreted NGF. Thus, many types of cells have the machinery to process and secrete NGF. However, NGF accumulated intracellularly (presumably in secretory granules) in cells with a regulated pathway of secretion (e.g., AtT-20 and HIT cells). In these cells, a membrane-permeable cyclic AMP analog, 8-bromo-cyclic AMP, stimulated NGF secretion. This suggests a mechanism for the regulation of NGF levels in which specific secretagogues, e.g., neurotransmitters, control NGF secretion.
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Affiliation(s)
- R H Edwards
- Department of Biochemistry, University of California, San Francisco 94143
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32
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Bagchi M, Caporale MJ, Dave AA, Niyogi TK, Putt D. The role of the iris-ciliary complex in the control of protein synthesis by the organ cultured rabbit ocular lens. Exp Eye Res 1988; 46:897-907. [PMID: 3197759 DOI: 10.1016/s0014-4835(88)80041-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
When freshly isolated rabbit lenses were co-cultured with iris-ciliary body (IC), the protein synthetic activity of these lenses decreased significantly. The inhibitory effect is temporal as longer incubation showed greater inhibition. it was also found that the presence of IC in the culture medium increases the sodium ion levels in the lenses and causes some decrease in the potassium ion levels. Both the protein synthetic activity and cation levels of the lenses cocultured with IC are at least partially reversible. It seems that the IC-derived factor(s) has a molecular weight of more than 1 kDa. It is not clear from these experiments whether the altered cation balance is responsible for the inhibition of the protein synthesis.
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Affiliation(s)
- M Bagchi
- Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201
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33
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Thoenen H, Bandtlow C, Heumann R, Lindholm D, Meyer M, Rohrer H. Nerve growth factor: cellular localization and regulation of synthesis. Cell Mol Neurobiol 1988; 8:35-40. [PMID: 3042143 DOI: 10.1007/bf00712909] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
1. The role of nerve growth factor (NGF) as a retrograde messenger between peripheral target tissues and innervating sympathetic and neural crest-derived sensory neurons is supported by the observations that (a) the interruption of retrograde axonal transport has the same effects as the neutralization of endogenous NGF by anti-NGF antibodies and (b) the close correlation between the density of innervation by fibers of NGF-responsive neurons and the levels of NGF and mRNANGF in their target organs. 2. In situ hybridization experiments have demonstrated that a great variety of cells in the projection field or NGF-responsive neurons is synthesizing NGF, among them epithelial cells, smooth muscle cells, fibroblasts, and Schwann cells. 3. The temporal correlation between the growth of trigeminal sensory fibers into the whisker pad of the mouse and the commencement of NGF synthesis initially suggested a causal relationship between these two events. However, in chick embryos rendered aneural by prior removal of the neural tube or the neural crest, it was shown that the onset of NGF synthesis in the periphery is independent of neurons, and is controlled by an endogenous "clock" whose regulatory mechanism remains to be established. 4. A comparison between NGF synthesis in the nonneuronal cells of the newborn rat sciatic nerve and that in the adult sciatic nerve after lesion provided evidence for the important regulatory role played by a secretory product of activated macrophages. The identity of this product is currently under investigation.
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Affiliation(s)
- H Thoenen
- Max-Planck-Institute for Psychiatry, Department of Neurochemistry, Martinsried, FRG
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34
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Dohrmann U, Edgar D, Thoenen H. Distinct neurotrophic factors from skeletal muscle and the central nervous system interact synergistically to support the survival of cultured embryonic spinal motor neurons. Dev Biol 1987; 124:145-52. [PMID: 3666302 DOI: 10.1016/0012-1606(87)90467-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Motor neurons isolated from 6-day-old embryonic chick spinal cords require muscle extract for survival in culture; however, it was found, that some motor neurons, identified by retrograde labeling with rhodamine, will survive in mixed spinal cell cultures in the absence of the extract. The motor neuron survival-promoting activity produced by spinal cells is soluble and differs from the factor present in muscle extract, the two activities acting in a synergistic manner: the spinal cell activity potentiated that of muscle to decrease its ED50 by an order of magnitude, the motor neuronal survival (30%) seen in the presence of both factors being more than the sum of their individual activities. This synergism was shown to be restricted to the action of the spinal cell factor on motor neurons, no effect of the factor being noted with sympathetic neurons. As a series of defined growth and survival factors present in the central nervous system (nerve growth factor, brain-derived neurotrophic factor, acidic and basic fibroblast growth factors) had no effect on motor neuron survival, we conclude that the molecule responsible for the motor neuron survival-promoting activity of the spinal cells is a previously undefined factor.
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Affiliation(s)
- U Dohrmann
- Max-Planck-Institute for Psychiatry, Department of Neurochemistry, Martinsried, Federal Republic of Germany
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35
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DAVIES ALUNM. Molecular and cellular aspects of patterning sensory neurone connections in the vertebrate nervous system. Development 1987. [DOI: 10.1242/dev.101.2.185] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- ALUN M. DAVIES
- Department of Anatomy, St George's Hospital Medical School, Cranmer Terrace, Tooting, London SW17 ORE, UK
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36
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Heumann R, Korsching S, Bandtlow C, Thoenen H. Changes of nerve growth factor synthesis in nonneuronal cells in response to sciatic nerve transection. J Cell Biol 1987; 104:1623-31. [PMID: 3034917 PMCID: PMC2114490 DOI: 10.1083/jcb.104.6.1623] [Citation(s) in RCA: 850] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The intact sciatic nerve contains levels of nerve growth factor (NGF) that are comparable to those of densely innervated peripheral target tissues of NGF-responsive (sympathetic and sensory) neurons. There, the high NGF levels are reflected by correspondingly high mRNANGF levels. In the intact sciatic nerve, mRNANGF levels were very low, thus indicating that the contribution of locally synthesized NGF by nonneuronal cells is small. However, after transection an increase of up to 15-fold in mRNANGF was measured in 4-mm segments collected both proximally and distally to the transection site. Distally to the transection site, augmented mRNANGF levels occurred in all three 4-mm segments from 6 h to 2 wk after transection, the longest time period investigated. The augmented local NGF synthesis after transection was accompanied by a reexpression of NGF receptors by Schwann cells (NGF receptors normally disappear shortly after birth). Proximal to the transection site, the augmented NGF synthesis was restricted to the very end of the nerve stump that acts as a "substitute target organ" for the regenerating NGF-responsive nerve fibers. While the mRNANGF levels in the nerve stump correspond to those of a densely innervated peripheral organ, the volume is too small to fully replace the lacking supply from the periphery. This is reflected by the fact that in the more proximal part of the transected sciatic nerve, where mRNANGF remained unchanged, the NGF levels reached only 40% of control values. In situ hybridization experiments demonstrated that after transection all nonneuronal cells express mRNANGF and not only those ensheathing the nerve fibers of NGF-responsive neurons.
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37
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Weskamp G, Otten U. An enzyme-linked immunoassay for nerve growth factor (NGF): a tool for studying regulatory mechanisms involved in NGF production in brain and in peripheral tissues. J Neurochem 1987; 48:1779-86. [PMID: 3572400 DOI: 10.1111/j.1471-4159.1987.tb05736.x] [Citation(s) in RCA: 301] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A sensitive enzyme-linked immunosorbent assay (ELISA) for nerve growth factor (NGF) has been developed. The sensitivity of this assay (0.1 pg/well) permits the quantification of endogenous immunoreactive NGF in the peripheral nervous system and the CNS. Studies on the regulatory mechanisms involved in NGF production indicate that, in addition to neurally mediated mechanisms, other stimuli, e.g., inflammation, significantly contribute to NGF production.
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38
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Vidovic M, Hill CE, Hendry IA. Developmental time course of the sympathetic postganglionic innervation of the rat eye. Brain Res 1987; 429:133-8. [PMID: 3567657 DOI: 10.1016/0165-3806(87)90146-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The time course of the innervation of the rat iris by sympathetic postganglionic axons from the superior cervical ganglion (SCG) has been studied in postnatal rats. A retrogradely transported fluorescent dye, Fast blue (FB) was injected bilaterally into the anterior eye chamber of rats within 3 h of birth or at 7 or 14 days postnatal. Littermates were killed at 24 h intervals, both SCG removed, fixed and sectioned. A substantial number of sympathetic neurones were labelled retrogradely from the eye at birth. The number of labelled cells tripled over the first postnatal week to reach proportions equivalent to those labelled in 3-week-old rats. The degree of sympathetic fibre ingrowth to the iris was examined at 3 postnatal ages, using fluorescence histochemistry. This method showed a small proportion of catecholamine-containing fibres in the iris at birth with a more extensive fibre density over the iris by 7 days after birth. A further increase in fibre density had occurred by the end of the 3rd postnatal week even though the number of cells projecting to the iris at these two ages was similar. This difference in fibre density may arise from ramification of fibres which have reached the iris by 7 days postbirth.
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39
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Thoenen H, Bandtlow C, Heumann R. The physiological function of nerve growth factor in the central nervous system: comparison with the periphery. Rev Physiol Biochem Pharmacol 1987; 109:145-78. [PMID: 3317757 DOI: 10.1007/bfb0031026] [Citation(s) in RCA: 393] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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40
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Grothe C, Unsicker K. Neuron-enriched cultures of adult rat dorsal root ganglia: establishment, characterization, survival, and neuropeptide expression in response to trophic factors. J Neurosci Res 1987; 18:539-50. [PMID: 2449541 DOI: 10.1002/jnr.490180406] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
It is unknown whether adult dorsal root ganglion (DRG) neurons require trophic factors for their survival and maintenance of neuropeptide phenotypes. We have established and characterized neuron-enriched cultures of adult rat DRGs and investigated their responses to nerve growth factor (NGF), ciliary neuronotrophic factor (CNTF), pig brain extract (PBE, crude fraction of brain-derived neuronotrophic factor, BDNF), and laminin (LN). DRGs were dissected from levels C1 through L6 and dissociated and freed from myelin fragments and most satellite (S-100-immunoreactive) cells by centrifugation on Percoll and preplating. The enriched neurons, characterized by their morphology and immunoreactivity for neuron-specific enolase, constituted a population representative of the in vivo situation with regard to expression of substance P (SP), somatostatin (SOM), and cholecystokinin-8 (CCK) immunoreactivities. In the absence of trophic factors and using polyornithine (PORN) as a substratum, 60-70% of the neurons present initially (0.5 days) had died after 7 days. LN as a substratum did not prevent a 30% loss of neurons up to day 4.5, but it subsequently maintained DRG neurons at a plateau. This behavior might reflect a cotrophic effect of LN and factors provided by non-neuronal cells, whose proliferation between 4.5 and 7 days could not be prevented by addition of mitotic inhibitors of gamma-irradiation. CNTF, but not NGF, slightly enhanced survival at 7 days on either PORN or LN. No neuronal losses were found in non-enriched cultures or when enriched neurons were supplemented with PBE, indicating that non-neuronal cells and PBE provide factor(s) essential for adult DRG neuron survival. Proportions of SP-, SOM-, and CCK-immunoreactive cells were unaltered under any experimental condition, with the exception of a numerical decline in SP cells in 7-day cultures with LN, but not PORN, as the substratum. Our data, considered in the context of recent in vivo and vitro studies, suggest that a combination of trophic factors or an unidentified factor, rather than the established molecules NGF, CNTF, and BDNF, which address embryonic and neonatal DRG neurons, are required for the in vitro maintenance of adult DRG neurons.
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Affiliation(s)
- C Grothe
- Department of Anatomy and Cell Biology, University of Marburg, Federal Republic of Germany
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41
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Dohrmann U, Edgar D, Sendtner M, Thoenen H. Muscle-derived factors that support survival and promote fiber outgrowth from embryonic chick spinal motor neurons in culture. Dev Biol 1986; 118:209-21. [PMID: 3770299 DOI: 10.1016/0012-1606(86)90089-8] [Citation(s) in RCA: 127] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The purposes of the experiments reported is to provide an unambiguous demonstration that embryonic skeletal muscle contains factors that act directly on embryonic spinal motor neurons both to support their survival and to stimulate the outgrowth of neurites. Cells of lumbar and brachial ventral spinal cords from 6-day-old chick embryos were separated by centrifugation in a two-step metrizamide gradient, and a motor neuron enriched fraction was obtained. Motor neurons were identified by retrogradely labeling with rhodamine isothiocyanate, and were enriched fourfold in the motor neuron fraction relative to unfractionated cells. In culture, the isolated motor neurons died within 3-4 days unless they were supplemented with embryonic chick skeletal muscle extract. Two functionally distinct entities separable by ammonium sulfate precipitation were responsible for the effects of muscle extracts on motor neurons. The 0-25% ammonium sulfate precipitate contained molecules that alone had no effect on neuronal survival but when bound to polyornithine-coated culture substrata, stimulated neurite outgrowth and potentiated the survival activity present in muscle. Most of this activity was due to a laminin-like molecule being immunoprecipitated with antisera against laminin, and immunoblotting demonstrated the presence of both the A and B chains of laminin. A long-term survival activity resided in the 25-70% ammonium sulfate fraction, and its apparent total and specific activities were strongly dependent on the culture substrate. In contrast to the motor neurons, the cells from the other metrizamide fraction (including neuronal cells) could be kept in culture for a prolonged time without addition of exogenous factor(s).
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Richardson PM, Verge VM. The induction of a regenerative propensity in sensory neurons following peripheral axonal injury. JOURNAL OF NEUROCYTOLOGY 1986; 15:585-94. [PMID: 3772404 DOI: 10.1007/bf01611859] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Injury of the peripheral axons of primary sensory neurons has been previously shown to increase the probability that the corresponding central axons would grow from the injured spinal cord into a peripheral nerve graft. This phenomenon has been used to investigate the nature of extrinsic cues from injured nerves that enhanced regenerative propensity within sensory neurons. In 13 groups of rats, a segment of the right sciatic nerve was grafted to the dorsal columns of the spinal cord and the left sciatic nerve was subjected to mechanical injury, injection of colchicine or infusion of nerve growth factor. Subsequently, neurons in lumbar dorsal root ganglia with axons growing from the spinal cord into a graft were identified by retrograde perikaryal labelling and compared for the two sides. The aim was to mimic or modify the inductive effect of nerve transaction by alternative or additional manipulation of the nerve. Growth of central axons was less enhanced by peripheral axonal interruption if the length of the proximal stump was increased or if a distal stump was present to permit rapid regeneration. However, the regenerative response following nerve transection was altered little by crushing the proximal stump or injecting it with colchicine or nerve growth factor. It is suggested that sensory neurons are stimulated to regenerate by peripheral axonal injuries that reduce some normal retrograde regulatory influence of Schwann cells.
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Tümmers U, Müller TH, Schmidt R, Seidl K, Lichtwald K, Vescei P, Wagner HJ, Unsicker K. Destruction of the preganglionic nerves by beta-bungarotoxin does not interfere with normal embryonic development of the rat adrenal medulla. Dev Biol 1986; 117:619-27. [PMID: 2875909 DOI: 10.1016/0012-1606(86)90330-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Using beta-bungarotoxin (beta-BTX) as a tool to eliminate the preganglionic cholinergic nerve supply to the embryonic rat adrenal gland, we have investigated whether or not these nerves affect the differentiation of embryonic chromaffin cells (pheochromoblasts). Rat fetuses received a single injection of 1 or 2 micrograms beta-BTX or an identical volume of saline at embryonic day (E) 17 and were taken for morphological and biochemical analyses at E 21. Administration of beta-BTX caused a 15 to 20% reduction in body weight, crown-rump-length and adrenal weight. Spinal cord development was reduced and acetylcholinesterase-positive cells in ventral and lateral columns were virtually absent in toxin-treated animals. In adrenal glands, a decrease of choline acetyltransferase activity to 13% of control levels and a concomitant decrease of ultrastructurally identifiable nerve fibers and axon terminals revealed that application of 2 micrograms beta-BTX effectively reduced the neuronal input to E 21 adrenal glands. Values for total adrenal catecholamines, relative amounts of adrenaline and noradrenaline, tyrosine hydroxylase and phenylethanolamine N-methyltransferase activities were unaltered. All ultrastructural features of pheochromoblasts (except the lack of synapse-like axon terminals) were inconspicuous. Corticosterone levels in adrenals and plasma were identical to controls. These data strongly suggest that normal embryonic development of adrenal chromaffin cells does not require an intact nerve supply.
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Heumann R, Thoenen H. Comparison between the time course of changes in nerve growth factor protein levels and those of its messenger RNA in the cultured rat iris. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67646-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abrahamson IK, Wilson PA, Rush RA. Production and transport of endogenous trophic activity in a peripheral nerve following target removal. Brain Res 1986; 392:117-26. [PMID: 3708372 DOI: 10.1016/0165-3806(86)90238-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
High concentrations of trophic factor for sympathetic neurones were found in the discrete nerve which innervates the expansor secundariorum muscle of the chicken wing. Mouse nerve growth factor (NGF) was additive with nerve extract in allowing survival of sympathetic neurones. Antiserum to NGF, while inhibiting outgrowth in response to NGF, only partially blocked survival promoted by the nerve extract. In these characteristics, the nerve extract resembled the previously characterized activity of its target organ. However, after surgical removal of the muscle there was no decrease in the concentration of trophic factors in the nerve 7 days later. Likewise sectioning, crushing or removing a piece of nerve 1 cm from the muscle had little effect on trophic levels after muscle removal. Retrograde transport of the activity occurred in the nerve even in the absence of the muscle. Distal to ligatures placed on the nerve stump 24 h earlier, 60% of the trophic activity was inhibited by an antiserum to mouse NGF suggesting that a chicken form of the molecule is present and transported. In culture, cells of the nerve sheath produced trophic factors, and the rate of production increased greatly during the first 24 h of incubation. Two conclusions are made: the major source of trophic activity in the nerve is Schwann cells and at least two molecules are present, one of which is a chicken form of NGF.
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Shelton DL, Reichardt LF. Studies on the regulation of beta-nerve growth factor gene expression in the rat iris: the level of mRNA-encoding nerve growth factor is increased in irises placed in explant cultures in vitro, but not in irises deprived of sensory or sympathetic innervation in vivo. J Cell Biol 1986; 102:1940-8. [PMID: 3700478 PMCID: PMC2114227 DOI: 10.1083/jcb.102.5.1940] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Beta-nerve growth factor (NGF) is a protein necessary for the survival and maintenance of sympathetic and sensory neurons that appears to be produced by the target tissues of these neurons in vivo. Both denervation and the culture of explants of one model target, the rat iris, leads to an increase in the NGF content, suggesting that innervating neurons may regulate a step in synthesis or turnover of NGF. To determine whether there is a change in synthesis controlled at the mRNA level, the rat iris has been assayed for its content of NGF mRNA after surgical and chemical denervation and after explant into culture. Using a sensitive blot hybridization assay, a large, rapid increase in the content of NGF mRNA was observed upon explant of the rat iris. The increase was readily detectable within 1 h, reached a maximum increase of 10- to 20-fold by 6 to 12 h, and was still evident after 3 d in culture. The distribution of NGF mRNA in different areas of the iris does not change during this time. This rapid increase in NGF mRNA is also seen in the fully innervated iris in vivo after trauma to the anterior chamber. In contrast, denervation to varying degrees in situ had no effect on NGF mRNA levels. Neither removal of sympathetic innervation by surgical or chemical methods nor combined surgical removal of sympathetic and sensory innervation detectably altered NGF mRNA content. Thus, denervation of the rat iris in situ does not cause the observed accumulation of NGF by increasing the level of NGF mRNA, and the increase in NGF content must be due to other factors.
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Murphy RA, Landis SC, Bernanke J, Siminoski K. Absence of the alpha and gamma subunits of 7S nerve growth factor in denervated rodent iris: immunocytochemical studies. Dev Biol 1986; 114:369-80. [PMID: 2420660 DOI: 10.1016/0012-1606(86)90201-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Immunocytochemical studies were performed to determine if denervated rodent iris produces nerve growth factor (NGF) in a form chemically similar to that of the 7S NGF complex in mouse submandibular glands. Antisera to the alpha, beta, and gamma subunits of 7S NGF were raised in rabbits and characterized on immunoblots of SDS-containing polyacrylamide gels. Antisera were applied to stretch preparations of rat and mouse irides that were cultured for periods of 2 to 6 days or sympathetically denervated by superior cervical ganglionectomy and left in situ 4 days. Antibody binding was visualized by indirect immunofluorescence. In control studies done on plastic sections of mouse submandibular glands, antisera co-localized the three subunits of 7S NGF within secretory granules of granular tubule cells. In denervated rat iris, beta NGF immunoreactivity was evident in a cellular plexus that resembled in distribution and morphology nerve fibers in the normal iris, in agreement with a previous study (R.A. Rush (1984). Nature (London) 312, 364-367). Identical staining patterns were observed in mouse iris. In neither rat or mouse, however, did the nerve-like processes stain with antibodies suggests that the NGF-like protein in denervated rodent iris is not synthesized as part of the 7S NGF complex. Iris also did not react with antibodies to epidermal growth factor, a protein co-localized with NGF in mouse submandibular glands and in guinea pig prostate.
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Finn PJ, Ferguson IA, Renton FJ, Rush RA. Nerve growth factor immunohistochemistry and biological activity in the rat iris. JOURNAL OF NEUROCYTOLOGY 1986; 15:169-76. [PMID: 2425058 DOI: 10.1007/bf01611653] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nerve growth factor (NGF) production in the cultured rat iris was examined using immunohistochemistry and bioassay of irides and conditioned media. NGF immunoreactivity increased steadily with days in culture so that the intensity of staining was maximal after 6 days of culture. The localization was shown to be sensitive to the presence of cross-linking fixatives such as formaldehyde and glutaraldehyde and this effect was only partially alleviated by the use of very high concentrations of antibodies. NGF immunoreactivity was localized in Schwann cells and possibly nerve axons, but with no antigen detectable in smooth muscle fibres. Media conditioned over irides initially supported a high percentage of dissociated sympathetic neurons, but the number supported decreased with time in culture until day 4. Moreover, the use of antibodies to NGF allowed the detection of at least two types of neuronotropic activity, NGF accounting for at least 94% of the total trophic activity present after 4 days of culture. These findings provide support for the proposal that Schwann cells produce NGF and question the accepted hypothesis that the molecule is produced by smooth muscle fibres as a peripheral maintenance factor for sympathetic and sensory nerves. The results also suggest that two survival factors may be involved in the regulation of sympathetic function.
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Wilson PA, Scott J, Penschow J, Coghlan J, Rush RA. Identification and quantification of mRNA for nerve growth factor in histological preparations. Neurosci Lett 1986; 64:323-9. [PMID: 3754318 DOI: 10.1016/0304-3940(86)90349-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Hybridization histochemistry has been used to detect mRNA for nerve growth factor (NGF) in histological preparations of mouse salivary glands and rat iris using a 32P-labelled cDNA probe and autoradiography. Label was visible over the tubular cells of the male mouse submaxillary gland but not the sublingual gland. A much lower label density was found over the tubular cells of the female submaxillary gland, whereas sections of liver and pancreas were negative. Quantitative autoradiography allowed the detection of low levels of mRNA for NGF in the rat iris which was elevated by prior culture of the tissue. The results provide direct histological evidence for the presence of specific NGF-mRNA in the mouse submaxillary gland and rat iris, with increased levels following culture.
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