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Cycling of dense core vesicles involved in somatic exocytosis of serotonin by leech neurons.

Trueta C, Kuffler DP, De-Miguel FF - Front Physiol (2012)

Bottom Line: A partial bleaching of the spots followed by another depolarization in the presence of FM1-43 produced restaining of some spots, other spots disappeared, some remained without restaining and new spots were formed.Several hours after electrical stimulation the FM1-43 spots accumulated at the center of the somata.This correlated with electron micrographs of multivesicular bodies releasing their contents near Golgi apparatuses.

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz," México D. F., México.

ABSTRACT
We studied the cycling of dense core vesicles producing somatic exocytosis of serotonin. Our experiments were made using electron microscopy and vesicle staining with fluorescent dye FM1-43 in Retzius neurons of the leech, which secrete serotonin from clusters of dense core vesicles in a frequency-dependent manner. Electron micrographs of neurons at rest or after 1 Hz stimulation showed two pools of dense core vesicles. A perinuclear pool near Golgi apparatuses, from which vesicles apparently form, and a peripheral pool with vesicle clusters at a distance from the plasma membrane. By contrast, after 20 Hz electrical stimulation 47% of the vesicle clusters were apposed to the plasma membrane, with some omega exocytosis structures. Dense core and small clear vesicles apparently originating from endocytosis were incorporated in multivesicular bodies. In another series of experiments, neurons were stimulated at 20 Hz while bathed in a solution containing peroxidase. Electron micrographs of these neurons contained gold particles coupled to anti-peroxidase antibodies in dense core vesicles and multivesicular bodies located near the plasma membrane. Cultured neurons depolarized with high potassium in the presence of FM1-43 displayed superficial fluorescent spots, each reflecting a vesicle cluster. A partial bleaching of the spots followed by another depolarization in the presence of FM1-43 produced restaining of some spots, other spots disappeared, some remained without restaining and new spots were formed. Several hours after electrical stimulation the FM1-43 spots accumulated at the center of the somata. This correlated with electron micrographs of multivesicular bodies releasing their contents near Golgi apparatuses. Our results suggest that dense core vesicle cycling related to somatic serotonin release involves two steps: the production of clear vesicles and multivesicular bodies after exocytosis, and the formation of new dense core vesicles in the perinuclear region.

No MeSH data available.


Related in: MedlinePlus

Perinuclear multivesicular bodies. (A) Multivesicular bodies (mvb) coexisting with Golgi apparatus (go). The multivesicular body on the right top contains mostly clear vesicles and is in association with endoplasmic reticulum (er) and mitochondria (m). The one in the right bottom has a membrane discontinuity (arrowhead). On the left side of the image, small vesicles near the Golgi endings (asterisks) display electrodense material inside. (B) Contents of the multivesicular bodies are in association with the nuclear membrane and near Golgi apparatus (n = nucleus). The arrowhead points to structures possibly binding the multivesicular body fragment with the nuclear membrane. Scale bars = 500 nm.
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Figure 8: Perinuclear multivesicular bodies. (A) Multivesicular bodies (mvb) coexisting with Golgi apparatus (go). The multivesicular body on the right top contains mostly clear vesicles and is in association with endoplasmic reticulum (er) and mitochondria (m). The one in the right bottom has a membrane discontinuity (arrowhead). On the left side of the image, small vesicles near the Golgi endings (asterisks) display electrodense material inside. (B) Contents of the multivesicular bodies are in association with the nuclear membrane and near Golgi apparatus (n = nucleus). The arrowhead points to structures possibly binding the multivesicular body fragment with the nuclear membrane. Scale bars = 500 nm.

Mentions: Correlating with the previous result, in neurons fixed 10 min after electrical stimulation had ended, multivesicular bodies were abundant deep in the perinuclear region, near Golgi apparatuses, vesicles, and mitochondria (Figure 8, see also Figure 1), right in the regions in which vesicles seem to be forming, as described above. The multivesicular bodies in some of the sections established links with Golgi elements, endoplasmic reticulum, and mitochondria. Their vesicle contents and degradation products with irregular shapes were apparently extruded from the multivesicular bodies and became a continuous with the vesicle accumulations aligned with the Golgi apparatus (Figure 8A). Multivesicular body fragments also appeared in the perinuclear region, making contacts with the nuclear membrane (Figure 8B). These structural associations suggest that the multivesicular body contents were recycled in the Golgi apparatus and also that some of their content contributed to communication between the nucleus and the extracellular space.


Cycling of dense core vesicles involved in somatic exocytosis of serotonin by leech neurons.

Trueta C, Kuffler DP, De-Miguel FF - Front Physiol (2012)

Perinuclear multivesicular bodies. (A) Multivesicular bodies (mvb) coexisting with Golgi apparatus (go). The multivesicular body on the right top contains mostly clear vesicles and is in association with endoplasmic reticulum (er) and mitochondria (m). The one in the right bottom has a membrane discontinuity (arrowhead). On the left side of the image, small vesicles near the Golgi endings (asterisks) display electrodense material inside. (B) Contents of the multivesicular bodies are in association with the nuclear membrane and near Golgi apparatus (n = nucleus). The arrowhead points to structures possibly binding the multivesicular body fragment with the nuclear membrane. Scale bars = 500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368391&req=5

Figure 8: Perinuclear multivesicular bodies. (A) Multivesicular bodies (mvb) coexisting with Golgi apparatus (go). The multivesicular body on the right top contains mostly clear vesicles and is in association with endoplasmic reticulum (er) and mitochondria (m). The one in the right bottom has a membrane discontinuity (arrowhead). On the left side of the image, small vesicles near the Golgi endings (asterisks) display electrodense material inside. (B) Contents of the multivesicular bodies are in association with the nuclear membrane and near Golgi apparatus (n = nucleus). The arrowhead points to structures possibly binding the multivesicular body fragment with the nuclear membrane. Scale bars = 500 nm.
Mentions: Correlating with the previous result, in neurons fixed 10 min after electrical stimulation had ended, multivesicular bodies were abundant deep in the perinuclear region, near Golgi apparatuses, vesicles, and mitochondria (Figure 8, see also Figure 1), right in the regions in which vesicles seem to be forming, as described above. The multivesicular bodies in some of the sections established links with Golgi elements, endoplasmic reticulum, and mitochondria. Their vesicle contents and degradation products with irregular shapes were apparently extruded from the multivesicular bodies and became a continuous with the vesicle accumulations aligned with the Golgi apparatus (Figure 8A). Multivesicular body fragments also appeared in the perinuclear region, making contacts with the nuclear membrane (Figure 8B). These structural associations suggest that the multivesicular body contents were recycled in the Golgi apparatus and also that some of their content contributed to communication between the nucleus and the extracellular space.

Bottom Line: A partial bleaching of the spots followed by another depolarization in the presence of FM1-43 produced restaining of some spots, other spots disappeared, some remained without restaining and new spots were formed.Several hours after electrical stimulation the FM1-43 spots accumulated at the center of the somata.This correlated with electron micrographs of multivesicular bodies releasing their contents near Golgi apparatuses.

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz," México D. F., México.

ABSTRACT
We studied the cycling of dense core vesicles producing somatic exocytosis of serotonin. Our experiments were made using electron microscopy and vesicle staining with fluorescent dye FM1-43 in Retzius neurons of the leech, which secrete serotonin from clusters of dense core vesicles in a frequency-dependent manner. Electron micrographs of neurons at rest or after 1 Hz stimulation showed two pools of dense core vesicles. A perinuclear pool near Golgi apparatuses, from which vesicles apparently form, and a peripheral pool with vesicle clusters at a distance from the plasma membrane. By contrast, after 20 Hz electrical stimulation 47% of the vesicle clusters were apposed to the plasma membrane, with some omega exocytosis structures. Dense core and small clear vesicles apparently originating from endocytosis were incorporated in multivesicular bodies. In another series of experiments, neurons were stimulated at 20 Hz while bathed in a solution containing peroxidase. Electron micrographs of these neurons contained gold particles coupled to anti-peroxidase antibodies in dense core vesicles and multivesicular bodies located near the plasma membrane. Cultured neurons depolarized with high potassium in the presence of FM1-43 displayed superficial fluorescent spots, each reflecting a vesicle cluster. A partial bleaching of the spots followed by another depolarization in the presence of FM1-43 produced restaining of some spots, other spots disappeared, some remained without restaining and new spots were formed. Several hours after electrical stimulation the FM1-43 spots accumulated at the center of the somata. This correlated with electron micrographs of multivesicular bodies releasing their contents near Golgi apparatuses. Our results suggest that dense core vesicle cycling related to somatic serotonin release involves two steps: the production of clear vesicles and multivesicular bodies after exocytosis, and the formation of new dense core vesicles in the perinuclear region.

No MeSH data available.


Related in: MedlinePlus