Exo-endocytosis in isolated peptidergic nerve terminals occurs in the sub-second range

1992 ◽  
Vol 12 (6) ◽  
pp. 495-501 ◽  
Author(s):  
Gerd Knoll ◽  
Helmut Plattner ◽  
Jean J. Nordmann
Keyword(s):  
Secretory Granules ◽  
Fluid Phase ◽  
Temporal Correlation ◽  
Nerve Terminals ◽  
Neurosecretory Granule ◽  
Minimal Time ◽  
Granule Membrane ◽  
Time Requirements ◽  
Time Required ◽  
Short Time

Exo- and endocytotic processes induced by depolarization of isolated neurosecretory nerve terminals show a close temporal correlation, which suggests a short time of integration of the neurosecretory granule membrane with the plasma membrane. In order to determine minimal time requirements for exocytosis-coupled endocytosis to occur, we have analyzed by electron microscopy uptake of horserdish peroxidase (HRP) as a fluid phase marker at the onset of depolarization. We have applied rapid mixing and sampling (quenched flow) to assess events in subsecond time peroids after stimulation. A significant number of labelled endocytotic vacuoles was observed during the first second of depolarization. This number then further increased by a factor of about 2 (within 5 s) and 4 (within 50s). Thus, as for exocytosis, the rate of endocytosis decreased considerably during prolonged stimulation. These data indicate i) that a substantial proportion of secretory granules undergoes exocytosis very shortly after stimulation, and ii) that, following exocytosis, the minimal time required for consecutive membrane retrieval is in the sub-second range.

Ultrastructural studies of the relationship between actin filaments and secretory granules

1990 ◽  
Vol 48 (3) ◽  
pp. 458-459
Author(s):  
Ellen Holm Nielsen
Keyword(s):  
Electron Microscopy ◽  
Colloidal Gold ◽  
Actin Filaments ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Granule Membrane ◽  
Ultrathin Sections ◽  
Lowicryl K4m

In secretory cells a dense and complex network of actin filaments is seen in the subplasmalemmal space attached to the cell membrane. During exocytosis this network is undergoing a rearrangement facilitating access of granules to plasma membrane in order that fusion of the membranes can take place. A filamentous network related to secretory granules has been reported, but its structural organization and composition have not been examined, although this network may be important for exocytosis.Samples of peritoneal mast cells were frozen at -70°C and thawed at 4°C in order to rupture the cells in such a gentle way that the granule membrane is still intact. Unruptured and ruptured cells were fixed in 2% paraformaldehyde and 0.075% glutaraldehyde, dehydrated in ethanol. For TEM (transmission electron microscopy) cells were embedded in Lowicryl K4M at -35°C and for SEM (scanning electron microscopy) they were placed on copper blocks, critical point dried and coated. For immunoelectron microscopy ultrathin sections were incubated with monoclonal anti-actin and colloidal gold labelled IgM. Ruptured cells were also placed on cover glasses, prefixed, and incubated with anti-actin and colloidal gold labelled IgM.

Effect of Vial shaking on Loading Time of Epirubicin into Drug-Eluting Bead

2015 ◽  
Vol 5 (3) ◽  
Author(s):  
Kenji Ikeda ◽  
Yusuke Kawamura ◽  
Masahiro Kobayashi ◽  
Taito Fukushima ◽  
Yushi Sorin ◽  
...  
Keyword(s):  
Antitumor Agent ◽  
Loading Rates ◽  
Vortex Mixer ◽  
Long Time ◽  
Group A ◽  
Drug Eluting ◽  
Large Hepatocellular Carcinoma ◽  
Group B ◽  
Time Required ◽  
Short Time

Background: Although DC Bead has been useful in treatment of multiple and large hepatocellular carcinoma, loading time of doxorubicin into the DC Bead takes a long time of 30-120 minutes. Epirubicin is also used as an antitumor agent together with DC Bead, but its loading efficiency was not sufficiently elucidated. Methods: To shorten loading time of epirubicin into DC Bead (100-300µm, 300-500µm, 500-700µm), we examined the following three methods after mixing the drug: (a) let stand in room temperature, (b) agitated for 30 seconds with Vortex mixer, and (c) sonicated for 30 seconds with ultrasonic cleaner. After loading of epirubicin by each method, supernatant concentration for epirubicin was assayed at 5, 10, 30, 60, and 120 minutes. Results: Epirubicin loading rates for small bead (100-300µm) at 5 minutes were 82.9 % in group a, 93.8% in group b, and 79.9 % in group c. Similarly, medium bead (300-500µm), 40.1% in group a, 65.7% in group b and 45.5% in group c, respectively. In large-sized bead (500-700µm), loaded rates of epirubicin were 38.8% in group a, 59.0% in group b and 48.0% in group c. Agitation of mixture of epirubicin and DC Bead with Vortex mixer significantly shortened the loading time, but sonication did not affect the time required. Microscopic examination did not lead to any morphological change of microspheres in all the methods. Conclusions: Short time of agitation with Vortex mixer reduced the necessary time for loading of epirubicin in every standard of DC Bead.

The adrenal paraneurone: tubulin organization

1984 ◽  
Vol 62 (5) ◽  
pp. 502-511 ◽  
Author(s):  
M. F. Bader ◽  
F. Bernier-Valentin ◽  
B. Rousset ◽  
D. Aunis
Keyword(s):  
Cell Body ◽  
Intracellular Transport ◽  
Cultured Cells ◽  
Specific Binding ◽  
Secretory Granules ◽  
Immunofluorescent Staining ◽  
Chromaffin Granules ◽  
Two Dimensional Gel Electrophoresis ◽  
Granule Membrane

When chromaffin cells from the bovine adrenal medulla are maintained in culture, they develop neuritelike processes which end with growth-cone-like structures. Chromaffin granules were found to migrate from the cell body to the neurite endings. Thus, the intracellular transport of secretory granules, existing in vivo, seems to occur in an exaggerated way in the cultured cells. These cells offer an excellent model for studying the mechanism of transport, particularly the role of microtubules. By immunofluorescent staining, we observed that tubulin antibodies decorate a complex network visible along the neurites. Colchicine treatment induced the disappearance of this network followed by a return of granules in the cell body and a retraction of neurites. To test the presence of tubulin in the chromaffin granule membrane, we used two-dimensional gel electrophoresis and a radioimmunoassay. Our results indicate that tubulin is not a significant component of chromaffin granules. However, binding experiments show that granule membranes are able to bind tubulin through high affinity binding sites. These results show that microtubules appear involved in neurite formation and probably in granule transport. Tubulin is not an integral constituent of the granule membrane, but is present as a result of a reversible specific binding. This insertion of tubulin into the membrane might represent a step in the association between microtubules and secretory granules.

scholarly journals The European TeleCheck-AF project on remote app-based management of atrial fibrillation during the COVID-19 pandemic: centre and patient experiences

EP Europace ◽  
2021 ◽  
Author(s):  
Monika Gawałko ◽  
David Duncker ◽  
Martin Manninger ◽  
Rachel M J van der Velden ◽  
Astrid N L Hermans ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Care Delivery ◽  
Patient Characteristics ◽  
Patient Experiences ◽  
Af Ablation ◽  
District Hospitals ◽  
Inclusion Rate ◽  
Set Up ◽  
Time Required ◽  
Short Time

Abstract Aims TeleCheck-AF is a multicentre international project initiated to maintain care delivery for patients with atrial fibrillation (AF) during COVID-19 through teleconsultations supported by an on-demand photoplethysmography-based heart rate and rhythm monitoring app (FibriCheck®). We describe the characteristics, inclusion rates, and experiences from participating centres according the TeleCheck-AF infrastructure as well as characteristics and experiences from recruited patients. Methods and results Three surveys exploring centre characteristics (n = 25), centre experiences (n = 23), and patient experiences (n = 826) were completed. Self-reported patient characteristics were obtained from the app. Most centres were academic (64%) and specialized public cardiology/district hospitals (36%). Majority of the centres had AF outpatient clinics (64%) and only 36% had AF ablation clinics. The time required to start patient inclusion and total number of included patients in the project was comparable for centres experienced (56%) or inexperienced in mHealth use. Within 28 weeks, 1930 AF patients were recruited, mainly for remote AF control (31% of patients) and AF ablation follow-up (42%). Average inclusion rate was highest during the lockdown restrictions and reached a steady state at a lower level after easing the restrictions (188 vs. 52 weekly recruited patients). Majority (>80%) of the centres reported no problems during the implementation of the TeleCheck-AF approach. Recruited patients [median age 64 (55–71), 62% male] agreed that the FibriCheck® app was easy to use (94%). Conclusion Despite different health care settings and mobile health experiences, the TeleCheck-AF approach could be set up within an extremely short time and easily used in different European centres during COVID-19.

Clinic Time Required for Remote and In-person Management of Cardiac Device Patients: A Time and Motion Workflow Evaluation (Preprint)

2021 ◽  
Author(s):  
David Lanctin ◽  
Eliana Biundo ◽  
Marco Di Bacco ◽  
Sarah Rosemas ◽  
Emmanuelle Nicolle ◽  
...  
Keyword(s):  
Patient Management ◽  
Clinic Visit ◽  
Future Research ◽  
Staff Time ◽  
Cardiac Device ◽  
Cardiac Implantable Electronic Devices ◽  
Time And Motion ◽  
Number Of Patients ◽  
Time Requirements ◽  
Time Required

BACKGROUND The number of patients with cardiac implantable electronic devices (CIEDs) is growing, creating substantial workload for device clinics. OBJECTIVE This study aimed to characterize the workflow and quantify clinic staff time requirements to manage CIED patients. METHODS A time and motion workflow evaluation was performed in 11 US and European CIED clinics. Workflow tasks were repeatedly timed during one business week of observation at each clinic. Observations were inclusive of all device models/manufacturers present. Mean cumulative staff time required to review a Remote device transmission and for an In-person clinic visit were calculated, including all necessary clinical and administrative tasks. Annual staff time for follow-up of 1 CIED patient was modeled using CIED transmission volumes, clinical guidelines, and published literature. RESULTS A total of 276 in-person clinic visits and 2,173 remote monitoring activities were observed. Mean staff time required per remote transmission ranged from 9.4-13.5 minutes for therapeutic devices (pacemaker, ICD, CRT) and 11.3-12.9 mins for diagnostic devices (insertable cardiac monitors (ICMs)). Mean staff time per in-person visit ranged from 37.8-51.0 mins and 39.9-45.8 mins, for therapeutic devices and ICMs respectively. Including all remote and in-person follow-ups, the estimated annual time to manage one CIED patient ranged from 1.6-2.4 hours for therapeutic devices and 7.7-9.3 hours for ICMs. CONCLUSIONS CIED patient management workflow is complex and requires significant staff time. Understanding process steps and time requirements informs implementation of efficiency improvements, including remote solutions. Future research should examine the heterogeneity in patient management processes to identify the most efficient workflows.

scholarly journals Sorting and storage during secretory granule biogenesis: looking backward and looking forward

1998 ◽  
Vol 332 (3) ◽  
pp. 593-610 ◽  
Author(s):  
Peter ARVAN ◽  
David CASTLE
Keyword(s):  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Secretory Proteins ◽  
Membrane Composition ◽  
Granule Formation ◽  
Granule Membrane ◽  
Regulated Secretory Pathway ◽  
Secretory Products

Secretory granules are specialized intracellular organelles that serve as a storage pool for selected secretory products. The exocytosis of secretory granules is markedly amplified under physiologically stimulated conditions. While granules have been recognized as post-Golgi carriers for almost 40 years, the molecular mechanisms involved in their formation from the trans-Golgi network are only beginning to be defined. This review summarizes and evaluates current information about how secretory proteins are thought to be sorted for the regulated secretory pathway and how these activities are positioned with respect to other post-Golgi sorting events that must occur in parallel. In the first half of the review, the emerging role of immature secretory granules in protein sorting is highlighted. The second half of the review summarizes what is known about the composition of granule membranes. The numerous similarities and relatively limited differences identified between granule membranes and other vesicular carriers that convey products to and from the plasmalemma, serve as a basis for examining how granule membrane composition might be established and how its unique functions interface with general post-Golgi membrane traffic. Studies of granule formation in vitro offer additional new insights, but also important challenges for future efforts to understand how regulated secretory pathways are constructed and maintained.

Chloride transport across the membrane of parotid secretory granules

1990 ◽  
Vol 259 (3) ◽  
pp. C413-C420 ◽  
Author(s):  
K. W. Gasser ◽  
U. Hopfer
Keyword(s):  
Chloride Transport ◽  
Secretory Granules ◽  
Disulfonic Acid ◽  
Parotid Glands ◽  
Transport Pathways ◽  
Anion Selectivity ◽  
Granule Membrane ◽  
Cytoplasmic Side ◽  
Cl Conductance

The Cl- transport pathways in secretory granules isolated from the parotid glands of rats were characterized by the technique of ionophore-induced lysis in defined salt solutions. The granules were shown to possess a Cl- conductance that exhibited a distinct anion selectivity with a sequence I- greater than Br- greater than Cl- greater than F- greater than SO4(2-) much greater than gluconate-. This conductance could be reduced approximately 40% by the stilbene 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) from the cytoplasmic side; the half-maximal concentration for inhibition was 50 microM. Furthermore, the apparent Cl- conductance was reduced by outwardly directed granule H+ gradients and stimulated by inwardly directed gradients. An outwardly directed H+ gradient mimics the in vivo environment and may serve in a regulatory capacity, providing for a tonic inhibition of transport until the granule fuses with the luminal membrane. The granules also possessed a Cl(-)-HCO3- exchange based on electroneutrality of Cl- uptake and stimulation of this uptake by HCO3-. This pathway displayed a different anion selectivity, I- greater than Br- greater than F- greater than Cl- much greater than SO4(2-) much greater than gluconate-, and was not inhibited by SITS on the cytoplasmic side. The presence of these electrolyte transport pathways in the granule membrane is consistent with the production of primary fluid by parotid acinar cells after fusion of granules with the luminal plasma membrane.

The Effect of Problem Complexity, Computer Power, and Feedback Aids on the Accuracy and Completness of Computer Programs

1982 ◽  
Vol 26 (11) ◽  
pp. 989-993
Author(s):  
Edward M. Connelly
Keyword(s):  
Task Force ◽  
Computer Programs ◽  
Problem Solution ◽  
Problem Complexity ◽  
User Input ◽  
Multi Level ◽  
Time Required ◽  
Short Time ◽  
Force Problem ◽  
Solution Specification

An essential step in the development of a computer program is the specification of the solution logic to be implemented by the program. The importance of accurate problem solution specification is further stressed by researchers in programming language and artificial intelligence who suggest that in a relatively short time computer programs will be synthesized automatically and that the job of the user will be only to specify the problem solution. The research reported in this paper involved an investigation of the ability of computer users to specify problem solutions in the form of example solutions. This ability was evaluated as a function of the user's background and experience, the complexity of the available processor (i.e., degree of generalization of the inputs), and the available feedback aids. Further, the ability of experienced programmers to implement the problem solution in FORTRAN IV logic code was investigated. The research reported here is part of study in multi-level communications, both abstract and concrete (i.e., general statements and examples), that may provide a method for effective two-way communication between users and computers. Two participant groups (programmers and bookkeepers/accountants) working with three levels of problem complexity and three levels of processor complexity were used. The experimental task employed in this study required specification of a logic for solution of a Navy task force problem. This task involved choosing ships from a ship list which identified the ship type, the transiting time (the time required for the ship to get from its present position to the desired site), and stationing time (the number of days the ship can remain on station with available provisions). In addition to this specification of ship combinations, the participants had to specify by the example solution the range of transiting and stationing times required. It was found that both programmers' and bookkeepers/accountants' scores decreased with increasing levels of problem and processor complexity, but the scores for the bookkeepers/accountants were significantly less than those of the programmers. In a regression analysis it was found that the degree of computer generalization of the user input (processor complexity) explained more variance than did problem complexity. Further for those experiment conditions where little computer generalization of user input was provided, performance was significantly lower than for other experiment conditions. This result suggests that computer generalization of user inputs is an important factor to accurate specification of problem solutions. Finally, the results show that participant strategy in generating solutions was the most significant factor affecting performance. The strategy measures, which indicated the degree of systematization of the participants, explained 58 percent of the score variance.

scholarly journals CONCOMITANT SYNTHESIS OF MEMBRANE PROTEIN AND EXPORTABLE PROTEIN OF THE SECRETORY GRANULE IN RAT PAROTID GLAND

1971 ◽  
Vol 50 (1) ◽  
pp. 187-200 ◽  
Author(s):  
Abraham Amsterdam ◽  
Michael Schramm ◽  
Itzhak Ohad ◽  
Yoram Salomon ◽  
Zvi Selinger
Keyword(s):  
Amino Acids ◽  
Secretory Granule ◽  
De Novo ◽  
Secretory Granules ◽  
Specific Radioactivity ◽  
Staining Intensity ◽  
Granule Membrane ◽  
Rat Parotid ◽  
Cell Fractions

After enzyme secretion the membrane of the secretory granule, which had been fused to the cell membrane, was resorbed into the cell. Experiments were therefore carried out to test whether formation of new secretory granules involves reutilization of the resorbed membrane or synthesis of a new membrane, de novo, from amino acids. Incorporation of amino acids-14C into proteins of various cell fractions was measured in vivo, 30, 120, and. 300 min after labeling. At all times the specific radioactivity of the secretory granule membrane was about equal to that of the granule's exportable content. At 120 and 300 min the specific radioactivity of the granule membrane and of the granule content was much higher than that of any other subcellular fraction. It is therefore concluded that the protein of the membrane is synthesized de novo concomitantly with the exportable protein. The proteins of the granule membrane could be distinguished from those of the granule content by gel electrophoresis. All major bands were labeled proportionately to their staining intensity. The amino acid composition of the secretory granule membrane was markedly different from that of the granule's content and also from that of the mitochondrial membrane. The granule membrane showed a high proline content, 30 moles/100 moles amino acids. The analyses show that the radioactivity of the granule membrane is indeed inherent in its proteins and is not due to contamination by other fractions. The possibility is considered that the exportable protein leaves the endoplasmic reticulum already enveloped by the newly synthesized membrane.

Sign in / Sign up

Export Citation Format

Share Document