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At least 343 records · Page 19Linked to original sources
PubMed1988

Altered reactivity of the rat adrenal medulla.

Previous studies have suggested that experimental alterations in adrenomedullary reactivity, i.e., changes in catecholamine release in response to a standard dose of acetylcholine, may be partially accounted for by changes occurring at the level of the adrenal medulla itself, independent of both the central nervous system and the innervation of the adrenal gland. The present study was designed to investigate the morphology of adrenal chromaffin cells in rats subjected to chronic hypoglycemia induced by long acting insulin, and to assess this morphology in terms of associated changes in catecholamine content and release. Surgically isolated, perfused adrenal gland preparations were utilized to characterize the functional release of catecholamines from the adrenal medulla. Pretreatment with long acting insulin resulted in a selective depletion of epinephrine stores and acetylcholine-mediated epinephrine release, but did not appear to significantly affect either the levels or the release of norepinephrine. The biochemical effects of long acting insulin persisted for several days after termination of the treatment, exhibiting a gradual recovery over a period of approximately 5 days. Electron microscopic examination of the adrenal chromaffin cells revealed a progressive degranulation and vacuolization of numerous chromaffin cells followed by a compensatory biosynthetic response and a gradual recovery toward the morphology of control cells. The functional release of catecholamines from adrenal chromaffin cells was further examined in preparations of perfused adrenal slices. Acetylcholine-mediated catecholamine release was significantly decreased in slices of adrenal glands prepared from insulin treated rats when compared with that of control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1997

Affinities of dopamine analogs for monoamine granular and plasma membrane transporters: implications for PET dopamine studies.

Affinities of dopamine (DA) analogs to both granular and plasma membrane uptake transporters were measured in vitro by inhibition of [3H]DA uptake in bovine chromaffin granule ghosts and C6 glial cells transfected with cDNA for the rat presynaptic dopamine transporter, respectively. Five amines were studied: DA, 6-fluorodopamine (6FDA), m-tyramine (MTA), 6-fluoro-m-tyramine (6FMTA), and beta-fluoromethylene-m-tyramine (FMMTA). Direct uptake of 18F labeled 6FDA and 6FMTA was also measured in the chromaffin granule system and compared with [3H]DA uptake. Results show that the transporter affinities of 6FDA and MTA were similar to that of DA in both transport systems while affinities of 6FMTA and FMMTA were lower. Furthermore while the direct uptake of DA and FDA in chromaffin granules were essentially identical and significantly reserpine-inhibitable, the direct uptake of 6FMTA was about 15-fold less and only minimally sensitive to reserpine pretreatment. Thus, although vesicular protection and reuptake may influence the turnover of FDA in 6-fluoroDOPA studies, they are unlikely to be important determinants of the kinetics of the slowly clearing components in studies with either 6-fluoro-m-tyrosine (6FMT) or 6-fluoro-beta-fluoro-methylene-m-tyrosine (6FFMMT), the bioprecursors of 6FMTA and 6-fluoro-FMMTA, respectively. These results are consistent with the finding that the longterm component in 6FMT PET studies is 6-fluoro-hydroxyphenylacetic acid (6FHPAC), which can be explained by the lack of vesicular protection of 6FMTA from MAO oxidation.

Animals↗
PubMed1990

[Adrenal medullary graft induces recovery of the host nigrostriatal dopaminergic system in MPTP-induced mouse model of Parkinson's disease].

C57BL/6 mice show decreased dopaminergic fibers and dopamine concentration in the striatum following systemic injection of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). We have investigated the effect of adrenal medullary grafts into the striatum of young mice treated with MPTP. Enhanced recovery of the host nigrostriatal dopaminergic system was observed in those adrenal medullary grafted mice. However, this recovery was influenced by the survivability of grafted chromaffin cells and adrenal chromaffin cells from younger donors survived better than those from older donors. Since adrenal chromaffin cells contain several kinds of neurotrophic factors such as basic fibroblast growth factor and gangliosides, survivability of those grafted chromaffin cells may play an important role concerning recovery of the host intrinsic dopaminergic fibers. Adrenal medullary grafts to the patients with Parkinson's disease are currently under way in a large number of hospitals and we suggest more consideration be given to methods which lead to enhance the grafted chromaffin cell survival, since those survivability might be closely related to the functional recovery of these patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

[The disseminated endocrine system of man. A contribution of pathology].

The disseminated (or diffuse) endocrine system is composed of many single cells and small groups of cells disseminated in the whole organism, capable of producing biogenic amines and polypeptide hormones. They are also called APUD cells and were first detected in the mucosa of the intestinal tract, where they occur in highest concentration. Carcinoids are tumors of disseminated endocrine cells which sometime retain their hormone-producing capacity. These hormones are key factors in the control of numerous bodily functions; some are transported by way of the bloodstream, while others probably exercise their functions only within the tissue immediately adjacent to the producing cells (paracrine function). It is an interesting fact that almost identical hormones are found within the brain and within the peripheral autonomic nervous system, where they act as neural transmitters.

APUD Cells↗
PubMed1978

The distribution and endocrine nature of the abdominal paraganglia of adult man.

The paraganglia of adult man were studied using the formaldehyde-induced fluorescence (FIF) method for histochemical characterization of biogenic monoamines. Microspectrofluorimetry was used to record the emission spectra and fluorescence intensities of the paraganglionic cells. The study of samples from six patients showed that well vascularized paraganglia were widely distributed throughout the retroperitoneal spaces. The paraganglia exhibited strong FIF with the spectral characteristics of monamines. Treatment with HC1 caused an increase in the fluorescence intensity of the paraganglia and a simultaneous shift of the emission maximum from 480--495 nm. This change suggests the presence of high concentrations of tryptophyl-containing peptides and is not due to monoamines. The possibility of a dual endocrine function for the paraganglia is discussed.

Abdomen↗
PubMed1984

Catecholamine-synthesizing enzymes in paraganglia of aged Fischer-344 rats. Immunohistochemistry and fluorescence microscopy.

The catecholamine-synthesizing enzymes, tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase were examined by immunohistochemistry in hypertrophied paraganglia of aged male Fischer-344 rats. All paraganglionic cells reacted with antibodies against tyrosine hydroxylase. Dopamine beta-hydroxylase was identified in most paraganglionic cells, indicating that they synthesized norepinephrine. A variable number of paraganglia were positive for phenylethanolamine-N-methyltransferase, which suggested that they synthesized epinephrine. The formaldehyde-induced fluorescence method demonstrated greenish-yellow fluorescence or yellowish-brown fluorescence. The intensity of the fluorescence was in the same range as in adrenal medullary cells. The observations indicate that paraganglia are capable of synthesizing epinephrine.

Animals↗
PubMed1980

Ultrastructure and histochemistry of human SIF cells and paraganglia.

The FIF method and electron microscopy were used to study SIF cells in the human sympathetic ganglia. In serial sections SIF cells in one ganglion often numbered less than 30, although they were found in every ganglion examined. Microspectrofluorimetry demonstrated the high catecholamine content in SIF cells. Electron microscopically these cells appeared as small granule-containing cells that receive a rich cholinergic type innervation. The diameter of the storage granules was 300 to 400 nm. In addition the SIF cells had close connections with each other. The SIF cells, situated solitary or as small clusters, were surrounded by satellite cells. Frequently the SIF cells located close to blood vessels.

Catecholamines↗
PubMed1993

Autonomic control of adrenal function.

Recent studies of adrenal function in conscious calves are reviewed. These have involved collecting the whole of the adrenal effluent blood from the right adrenal gland at intervals and, where necessary, prior functional hypophysectomy by destruction of the pituitary stalk under general halothane anaesthesia 3 d previously. The adrenal medulla was found to release numerous neuropeptides, in addition to catecholamines, in response to stimulation of the peripheral end of the right splanchnic nerve, which was carried out below behavioural threshold. Many of these responses were enhanced by stimulating intermittently at a relatively high frequency. Intra-aortic infusions of a relatively low dose of acetylcholine (4.5 nmol min-1 kg-1) elicited similar responses. In the adrenal cortex, agonists which either potentiated the steroidogenic response to ACTH or exerted a direct steroidogenic action included VIP, CGRP, CRF and ACh acting via muscarinic receptors. Stimulation of the peripheral end of the right splanchnic nerve strongly potentiated the steroidogenic response to ACTH and there is compelling evidence that the innervation normally plays an important part in cortisol secretion.

Acetylcholine↗