The ultrastructural organization of the rat exocrine pancreas

Ekholm, R.; Zelander, T.; Edlund, Y

doi:10.1016/s0022-5320(62)80028-8

Cited by 66 publications

(26 citation statements)

References 3 publications

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“…This type of intracellular transfer is well established for various secretory cells and may be adopted also for the hepatocyte. Recent investigations have shown that secretory vesicles fuse with each other during secretion in mast cells [4] exocrine [5,6] and endocrine pancreatic tissue [7] . The intervesicular fusion provides a tool for studies on membrane fusion, since Colgi-derived vesicles can be isolated from the hepatocyte and their interaction with various agents, suggested to trigger membrane fusion, can be monitored by freeze-cleaving.…”

Section: Introductionmentioning

confidence: 99%

Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Gratzl

Dahl

1976

FEBS Letters

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Section: Introductionmentioning

confidence: 99%

Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Gratzl

Dahl

1976

FEBS Letters

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“…11) . Although they seemed to be more abundant [2][3][4][5][6] hr after the onset of secretion (Fig . 9), their occurrence is as yet not clearly correlated with the secretory cycle .…”

mentioning

confidence: 99%

Dynamic Changes in the Ultrastructure of the Acinar Cell of the Rat Parotid Gland During the Secretory Cycle

Amsterdam

Ohad

Schramm

1969

The Journal of Cell Biology

417

129

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Synchronization of the secretory cycle in vivo was obtained by injecting isoprenaline as an inducer of secretion . A quantitative correlation between enzyme release, its subsequent reaccumulation, and the sequence of ultrastructural changes was found . At the ultrastructural level secretion was paralleled by depletion of zymogen granules through fusion of the granule membrane with the lumen membrane and discharge of the content . Each zymogen granule membrane, once connected with the lumen, acted as a lumen membrane . Fusion was thus sequential and resulted in a dramatic enlargement of the lumen space . During the entire process the passage between the lumen and the intercellular space remained blocked by the tight junctions, as shown by their impenetrability to ferritin . Reduction of the lumen size following enzyme discharge seemed to be achieved by withdrawal of lumen membrane in the form of small smooth vesicles which appeared mostly in the apical part of the cell . At the same time, the cell retracted towards the lumen, the whole process being completed within 2 hr from onset of secretion . Disappearance of the smooth vesicle followed, concomitant with formation of many condensing vacuoles and appearance of mature zymogen granules . The fate of the zymogen granule membrane, including its fusion with the lumen membrane, resorption in the form of small smooth vesicles, and its eventual reutilization mediated by the Golgi system, is discussed .

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“…Exocytosis requires the fusion of the vesicle membrane with the plasma membrane. However, as already shown in several cells, the stimulus for secretion not only induces the fusion of the plasma membrane with the vesicular membrane but also of secretory vesicles among themselves [2,3,6,18,29,39,53,65]. Thus the exocytotic process appears to involve both types of fusions.…”

Section: Discussionmentioning

confidence: 69%

“…8a). The twinned structure of completely fused vesicles does not differ from that found in stimulated secretory cells [2,3,6,12,18,29,39,53,65]. Magnification of Fig.…”

Section: Effect Of Group-spec~c Reagents and Enzymesmentioning

confidence: 70%

“…Intervesicular fusion of secretory vesicles, as well as the interaction between the cell membrane and the vesicle membrane, was observed in a variety of secretory cells [2,3,6,18,29,39,53,65]. Douglas [20] showed that in "compound exocytosis" by mast cells an external stimulus initiates fusion between secretory vesicle membranes and the 0022-2631/78/0040-0343 $4.40 9 Springer-Verlag New York Inc.…”

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confidence: 99%

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Fusion of secretory vesicles isolated from rat liver

Gratzl

Dahl

1978

J. Membrain Biol.

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Summary. Secretory vesicles isolated from rat liver were found to fuse after exposure to Ca 2 +. Vesicle fusion is characterized by the occurrence of twinned vesicles with a continuous cleavage plane between two vesicles in freeze-fracture electron microscopy. The number of fused vesicles increases with increasing Ca 2 +-concentrations and is half maximal around 10 -6 M. Other divalent cations (Ba 2+, Sr 2+, and Mg 2+) were ineffective. Mg 2+ inhibits Ca2+-induced fusion. Therefore, the fusion of secretory vesicles in vitro is Ca z+ specific and exhibits properties similar to the exocytotic process of various secretory cells.Various substances affecting secretion in vivo (microtubular inhibitors, local anesthetics, ionophores) were tested for their effect on membrane fusion in our system.The fusion of isolated secretory vesicles from liver was found to differ from that of pure phospholipid membranes in its temperature dependence, in its much lower requirement for Ca 2+, and in its Cag+-specificity. Chemical and enzymatic modifications of the vesicle membrane indicate that glycoproteins may account for these differences.Membrane fusion is an essential event in a variety of cell functions such as cell fusion, uptake of extracellular material (endocytosis) and release of cell products (exocytosis). Elucidation of the molecular mechanism of membrane fusion has been hampered by the lack of suitable systems for studying this process. Studies with intact cells have not yielded data which lead to ready interpretation concerning subcellular processes. On the other hand, studies with artificial membranes may be only tangentially related to the fusion of biological membranes.Recently our group investigated the fusion of isolated biological membranes [16,17,31,33,69,74]. We observed that Ca 2+ specifically induces the fusion of isolated secretory vesicles in a buffered sucrose medium.Intervesicular fusion of secretory vesicles, as well as the interaction between the cell membrane and the vesicle membrane, was observed in a variety of secretory cells [2,3,6,18,29,39,53,65]. Douglas [20] showed that in "compound exocytosis" by mast cells an external stimulus initiates fusion between secretory vesicle membranes and the

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The ultrastructural organization of the rat exocrine pancreas

Cited by 66 publications

References 3 publications

Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Dynamic Changes in the Ultrastructure of the Acinar Cell of the Rat Parotid Gland During the Secretory Cycle

Fusion of secretory vesicles isolated from rat liver

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The ultrastructural organization of the rat exocrine pancreas

Cited by 66 publications

References 3 publications

Ca2+‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Ca2+‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Dynamic Changes in the Ultrastructure of the Acinar Cell of the Rat Parotid Gland During the Secretory Cycle

Fusion of secretory vesicles isolated from rat liver

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Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

Ca²⁺‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver