ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90001-4

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThis introductory article presents a survey of the principle cellular constituents of the sympathoadrenal section in the peripheral autonomic nervous system, their development and plasticity and factors that govern the expression of particular morphologic and transmitter phenotypes. The article focuses on results obtained in cell culture studies with isolated chromaffin cells that have permitted the analysis of molecular signals possibly serving as environmental cues during the development of sympathoadrenal cells.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90002-6

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractA descriptive account and morphometric study of the adrenal medulla and adrenal chromaffin cells of Wistar rats aged from birth to 22 months is presented. Distinct adrenaline and noradrenalinestoring types of chromaffin cells are first identified in 4‐day‐old animals, prior to that time individual cells contain both adrenaline‐ and noradrenaline‐storing granules. Primitive sympathetic cells and phaeochromoblasts occur up to 2 days postnatally. Mitotic figures occur in chromaffin cells of a maturity and appearance appropriate to age and most frequently in adrenaline‐storing cells. The adrenal medulla continues to increase in volume throughout the period and chromaffin cells increase in number and in some cases volume. There is a corresponding increase in neuronal elements. In 22‐month‐old rats individual cells or groups of chromaffin cells show evidence of hypertrophy and changes in cytoplasmic organelles, in particular lysosomes, rough endoplasmic reticulum and storage granules and vesicles. Some hypertrophied chromaffin cells contain a heterogeneous population of granules suggesting a degree of functional plasticity in some cells in aged rats.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90003-8

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractEpinephrine and norepinephrine‐containing chromaffin cells proliferate in the adrenal glands of normal adult rats throughout life. Moreover, their rate of proliferation is markedly increased by short‐term administration of reserpine, one of many agents which in long‐term experiments are associated with the development of adrenal medullary tumors. Current data suggest that chromaffin cell proliferation in the adult rat adrenal is mediated by the interaction of neurogenic and hormonal signals. Reserpine is known to directly deplete catecholamine stores, and to reflexively increase the activity of the splanchnic nerve endings innervating the adrenal medulla to stimulate both secretion and synthesis of catecholamines and other secretory granule constituents. Its effect on chromaffin cell proliferation suggests that the same signals may regulate chromaffin cell number to meet physiological needs. The reserpine model might shed light on signal transduction mechanisms which normally promote or prevent proliferation of chromaffin cells and of other neuroendocrine cells during development or in adult life, and on ways in which such mechanisms are altered in the course of the development and progression of tumors. It also suggests the possibility that chromaffin cells might be propagatedin vitrofor use in basic biological studies or in transplants for the treatment of Parkinson's disease.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90004-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractLong‐term neural crest cultures grown in the continuous absence of exogenous nerve growth factor (NGF) contain a subpopulation of cells with NGF receptors exclusively of the low affinity subtype (dof approximately 3.2 nM). The current studies combined immunocytochemistry, using GIN1 (a support cell marker) or tyrosine hydroxylase antibodies, with radioautography following exposure to iodinated nerve growth factor (125I‐NGF). The majority of cells specifically binding125I‐NGF were found to be immunoreactive for GIN1, indicating that the primary cell phenotype expressing receptors for NGF appear to be support cell precursors, at least under these conditions. These cells are likely to be responsive to and/or dependent upon NGF; the nature of this response or dependency remains to be determined. Some cells exhibiting silver grains were not immunoreactive for GIN 1, suggesting that other cell phenotypes in neural crest cultures also have NGF receptors. In addition, some neural crest cells were found that stained with GIN1 and lacked125I‐NGF binding. Tyrosine hydroxylase‐like immunoreactive cells apparently did not bind1251‐NGF under these culture conditions. Catecholaminergic sympathetic and sensory neurons from embryonic ganglia, derived from the neural crest, express both the high and low affinity forms of the NGF receptor. In order to determine whether the microenvironment played a role in the type of Catecholaminergic cells appearing in culture, neural crest cells were grown in the continuous presence of exogenous NGF. Under these conditions, many tyrosine hydroxylase‐like immunoreactive cells were found that specifically bound125I‐NGF. In addition, silver grains were still detected on these cells following a chase with nonradioactive NGF, designed to eliminate125I‐NGF bound to low affinity sites. Therefore, the Catecholaminergic cells possess both the low and high affinity forms of the receptor. NGF's ability to modulate tyrosine hydroxylase activity, as it does in mature Catecholaminergic neurons, was tested in this system. Surprisingly, there was no statistically significant difference in tyrosine hydroxylase activity in cultures grown in the absence or presence of exogenous NGF. This raises the possibility that embryonic Catecholaminergic cells are unable to respond to NGF in this specific way, even though the receptors for the factor are present.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90005-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractChromaffin precursor cells from embryonic rat adrenal glands were isolated at 16.3 and 20.3 days of gestation and purified by centrifugation on density gradients. Approximately 50% of the cells of both age groups that had attached to the culture substratum by 12 hr survived during a 4‐day culture period in the absence of exogenous trophic factors. Nerve growth factor (NGF) and a C6 glioma‐cell‐conditioned medium (C6‐CM) had no or a very moderate promoting effect on survival. The gluco‐corticoid dexamethasone (DEX) supported the survival of 70–80% of the cells that otherwise would have died. Spontaneous neuritic growth of the sympathoadrenal precursor cells was significantly more pronounced with cells isolated at embryonic day (E) 16.3 than at E20.3. NGF had a significantly smaller promoting effect on neurite ougrowth at E16.3 than at E20.3. C6‐CM induced neurite outgrowth from 25% (E16.3) and 35% (E20.3) of the surviving cells. DEX (10−6M) completely abolished spontaneous neuritic growth and partially suppressed C6‐CM‐mediated fiber outgrowth. These data underscore the importance of glucocorticoids for the maintenance and development of an endocrine morphologic phenotype of sympathoadrenal precursors. They suggest that the cells may be initially driven by growth factors other than NGF into a neuronal direction and that they lack NGF‐responsiveness and dependence during the early stages of their development.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90006-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractChromaffin cells and sympathetic neurons develop from a common neural crest‐derived progenitor cell. The developmental fate of this cell differs depending upon whether it migrates to the sympathetic ganglion or to the adrenal gland primordium, suggesting that local environmental signals control its differentiation. Glucocorticoid (GC) is a good candidate for an important adrenal environmental signal. These steroids are known to regulate PNMT, an adrenal‐specific enzyme. However,in vivoobservations suggest that the adrenal microenvironment influences the phenotype of sympathoadrenal progenitor cells as early as E14.5, 2 days before PNMT is first expressed by developing chromaffin cells. Using cDNA probes, we find that GC receptor mRNA can be detected in the embryonic adrenal at least one full day before the initial appearance of PNMT mRNA. This observation is compatible with the idea that the apparent early influence of the adrenal microenvironment reflects the action of GC on progenitors which have migrated into this environment. In support of this, we show that similar influences can be exerted by GC on PC12 cells, which contain GC receptor mRNA but do not express or induce PNMT mRNA. Taken together, these data suggest that other factors in addition to the presence of the GC receptor may be necessary for the developmental appearance of PNMT expression.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90007-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe ontogenic expression of proenkephalin A (ProEnk A) mRNA and phenylethanolamine N‐methyltransferase (PNMT) mRNA was examined in the foetal sheep adrenal medulla by the use of specific oligodeoxyribonucleotide probes. Northern blot analysis of RNA extracts from foetal adrenals demonstrated that ProEnk A mRNA was expressed as early as 60 days of gestation, a time at which the foetal adrenal is not functionally innervated.In situhydridization on sections of foetal adrenals revealed that at 110–140 days gestation ProEnk A mRNA was expressed in chromaffin cells at the outer margin of the adrenal medulla but at earlier stages of gestation (e.g. 95 days) appeared to be expressed homogeneously throughout the whole of the adrenal medulla. In comparison, PNMT mRNA was expressed preferentially in cells at the outer margin of the adrenal medulla from the earliest stage detectable. Both PNMT mRNA and ProEnk A mRNA co‐localized in cells at the outer margin of foetal adrenal of late gestations (110–140 days), a similar pattern to that seen in the adult adrenal medulla. These results indicate that, as with adult animals, in foetuses of late gestation, adrenal enkephalins are co‐stored within adrenaline cells. It is likely therefore that enkephalins are co‐released from the foetal adrenal with adrenaline in response to intra‐uterine stress.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90008-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractTransmitter phenotypic expressions is a dynamic cellular process governed by multiple interactions with the neuronal environment. During sympathoadrenal development the arrival of presynaptic nerve terminals at the adrenal chromaffin cell (in the immediate postnatal period), coincides with the acquisition and subsequent development of a variety of transmitter biosynthetic capacities. Data discussed herein supports the contention that synaptic connections serve a central role in triggering the ontological cascade. Disruption of the normal timing of innervation events is detrimental to subsequent function and results in permanent deficiencies in development. In addition, alteration of transmitter biosynthetic regulatory mechanisms appears to reside at the level of gene expression. In view of this, additional molecular approaches are necessary to further elucidate the fundamental basis of neuronal transmitter phenotypic plasticity. Our approach to this problem represents a logical extension of previous research in this area and ultimately, will involve characterizing transcription activator molecules important in transmitter gene expression at various ontological ages.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90009-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIn the adrenal medulla of adult rat, physiological levels of glucocorticoid hormones are required to maintain the catalytic activity of the epinephrine‐synthesizing enzyme, phenylethanolamine N‐methyltransferase (PNMT). The present study was undertaken to determine whether glucocorticoid regulation of PNMT occurs at the level of mRNA coding for PNMT. Adult male Sprague‐Dawley rats were hypophysectomized (HPX) and killed after 2 weeks; pellets of corticosterone were implanted for 1, 3 or 7 days prior to killing. Determinations were made of plasma corticosterone levels, adrenal PNMT activity and PNMT mRNA levels by Northern gel analysis. HPX resulted in a decrease in plasma corticosterone to undetectable levels and decreases in PNMT activity and PNMT mRNA levels to 1 and 18% of the levels observed in sham rats, respectively. Corticosterone replacement produced high prolonged plasma levels of corticosterone which were 10 times those of sham rats, and significantly increased levels of PNMT activity and mRNA. However, corticosterone replacement failed to restore PNMT activity and mRNA levels fully.These results suggest that the maintenance of PNMT mRNA levels is dependent on maintaining corticosterone levels and supports the hypothesis that PNMT gene expression in the adrenal medulla is directly regulated by glucocorticoids produced by the adrenal cortex. However, the results also suggest that in the chronically HPX rat, factors in addition to naturally produced glucocorticoids are required for full restoration of PNMT mRNA levels.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90010-5

出版商:Wiley    

年代:2003

数据来源: WILEY