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1
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The molecular mechanism of nondegranulative release of biogenic amines

100%
Uvnas B.
Journal of Physiology and Pharmacology
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1991
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tom 42
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nr 2
According to current teaching biogenic amines are released by exocytos- is, i. e. by evacuation of amine storing vesicles or granules into the extracellular space. The release of transmitter amines is quantal, i. e. occurs in packs of transmitter molecules. These packs are assumed to be identical with vesicle contents, in other words, the smallest releasable quantum equals the amine content of one vesicle. However, there are experimental observations which do not fit in with this version of an exocytotic release theory. Observed quantitative discrepancies could be explained if the release mechanism allowed a fractional release of transmitter amine from several vesicles instead of the total evacuation of a few. The lack of adequate knowledge about the mechanisms of storage of biogenic amines within the vesicles has up til now rendered it difficult to envisage the machinery behind a fractional release of the amine content of a vesicle. In extensive in-vitro studies we have found that the matrices of amine storing granules (i. e. from mast cells, chromaffin cells and nerve terminals) show the properties of weak cation exchanger materials, carboxyl groups serving as amine binding ionic sites. When exposed to cations like sodium and potassium ions, the amines are released from their storage sites according to kinetics characteristic of weak cation exchangers. In vivo, amine release from cat adrenals on splanchnic nerve stimulation also occurs according to ion echange kinetics. Histamine release from mast cells is considered to occur as the result of degranulation, i. e. the expulsion of histamine storing granules to the extracellular space, a typical example of exocytosis. The granules are assumed to loose their histamine by ion exchange, Na⁺ Hi⁺, on exposure to the sodium-rich extracellular medium. However, recent observations on histamine release from superfused mast cells suggest that the release of histamine, although caused by ion exchange, is due to intracellular ion exchange at granule sites between cytoplasmic potassium and activated mast cells as the consequence of intracellular potassium ion flux across the histamine carrying granules, degranulation and extracellular histamine release from expelled granules occurring only as the result of more extensive activation. The possibility of potassium ions being involved also in an ion exchange process behind the release of other biogenic amines e. g. at nerve terminals will be proposed. The amine release will still be quantal but the size of the released quanta will not depend on the total amine content of a vesicle but on the size of the fractions thereof being released, thereby explaining many of the quantitative discrepancies attached to the current exocytotic release theory. A fractional release theory may have interesting consequences for our thinking as to the physiology and pharmacology of processes involving storage and release of biogenic amines.
2

APUD cells in the ovary of white rat

84%
Wrutniak-Zolnowska T.
Folia Morphologica
|
1986
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tom 45
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nr 1
3

Myosin VI is associated with secretory granules and is present in the nucleus in adrenal medulla chromaffin cells

84%
Majewski L., Sobczak M., Redowicz M. J.
Acta Biochimica Polonica
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2010
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tom 57
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nr 1
109-114
Myosin VI (MVI) is the only known myosin walking towards minus end of actin filaments. Here, MVI, but not myosins IB or IIB, was detected in chromaffin granules isolated from bovine medulla and found to be tightly associated with the granule apical surface. MVI also localized to secretory granules within rat pheochromocytoma PC12 cells as well as to the Golgi apparatus, endoplasmic reticulum and clathrin-coated pits. Notably, it was also found in the nucleus. RT-PCR revealed that MVI splice variants with a large insert (LI), characteristic of polarized cells, were barely detectable in PC12 cells, whereas variants with a small insert (SI) were the major isoforms. The presented data indicate that MVI in adrenal medulla cells is engaged in secretory vesicle trafficking within the cytoplasm and possibly also involved in transport within the nucleus.
4

The cellular composition of the adrenal medulla of sexually mature guinea pigs

84%
Kmiec B. L., Kaczmarczyk D.
Folia Morphologica
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2004
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tom 63
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nr 1
The adrenal glands from 15 guinea pigs aged 90 days were used in the study. Paraffin slices were stained with Mayer haematoxylin and eosin with Masson method and silvered. The histochemical reactions were carried out for catecholamines and the biochemical determinations of catecholamines. Ultrastructural observations were also performed. In the adrenal medulla of sexually mature guinea pigs numerous epinephrocites and no noreoinefrocites were observed when histochemical methods were used. The small and large ganglion cells accompanying the supporting and neurolemmal cells formed typical gangliar weaving (medullary ganglia). Apart from epinephrocytes, small and large ganglion cells and supporting and neurolemmal cells, small intensively fluorescent (SIF) cells were also detected. Biochemical investigation revealed that the mean content of adrenaline calculated for a pair of adrenal glands was 98.87% of the pool of catecholamines, whereas the mean content of noradrenaline was 1.00%, and of dopamine 0.13%.
5
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Mechanisms of catecholamine secretion from chromaffin cells

84%
Burgoyne R. D.
Journal of Physiology and Pharmacology
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1995
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tom 46
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nr 3
6

Morphochemical investigations on postnatal development of the adrenal medulla in guinea pigs

84%
Kaczmarczyk D., Kmiec B. L.
Folia Histochemica et Cytobiologica. Supplement
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1996
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tom 34
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nr 1
7

Histochemical and biochemical investigations on postnatal development of the adrenal medulla in guinea pigs

67%
Kaczmarczyk D., Kmiec B. L.
Acta Biologica Cracoviensia. Series Botanica et Zoologia. Supplement
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1997
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tom 39
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nr 1
8
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Noradrenaline and ATP: contransmitters and neuromodulators

59%
Burnstock G.
Journal of Physiology and Pharmacology
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1995
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tom 46
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nr 4
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