The Secretory Process in Platelets

2015 ◽  
pp. 546-569
Author(s):  
James G. White
Keyword(s):  
Secretory Process

A T.E.M. study of mouse mammary epithelial cell secretory differentiation cultured on collagen and Matrigel

1991 ◽  
Vol 49 ◽  
pp. 188-189
Author(s):  
W.N. Bentham ◽  
V. Rocha
Keyword(s):  
Cell Culture ◽  
Mammary Epithelial ◽  
Secretory Process ◽  
Cell Culture System ◽  
Protein Maturation ◽  
Cell Culture Techniques ◽  
Culture Techniques ◽  
Mouse Mammary Epithelial Cell ◽  
Secretory Differentiation

It has been an interest of our lab to develop a mammary epethelial cell culture system that faithfully duplicates the in vivo condition of the lactating gland. Since the introduction of collagen as a matrix on which cells are cultivated other E.C.M. type matrices have been made available and are used in many cell culture techniques. We have previously demonstrated that cells cultured on collagen and Matrigel do not differentiate as they do in vivo. It seems that these cultures often produce cells that show a disruption in the secretory process. The appearance of large ribosomal studded vesicles, that specifically label with antibody to casein, suggest an interruption of both protein maturation and secretion at the E.R. to golgi transition. In this report we have examined cultures on collagen and Matrigel at relative high and low seeding densities and compared them to cells from the in vivo condition.

Inhibition of atrial peptide secretion at different stages of the secretory process: Ca2+ dependence

1991 ◽  
Vol 261 (6) ◽  
pp. C1162-C1172 ◽  
Author(s):  
E. Page ◽  
J. Upshaw-Earley ◽  
G. E. Goings ◽  
D. A. Hanck
Keyword(s):  
Protein Synthesis ◽  
Brefeldin A ◽  
Atp Depletion ◽  
Secretory Process ◽  
Protein Synthesis Inhibitors ◽  
Large Reservoir ◽  
Secretory Rate ◽  
Vesicular Traffic ◽  
Dependent Inactivation

We have used a noncontracting in vitro preparation of stretched and unstretched rat atria to estimate contributions of constitutive and regulated pathways to the rates of stretch-augmented and basal secretion of immunoreactive atrial natriuretic peptide (ANP) and to examine effects of inhibition of the secretory sequence by 1) protein synthesis inhibitors, 2) disruption of forward vesicular traffic between endoplasmic reticulum and Golgi with brefeldin A (BFA, and 3) cellular ATP depletion. Protein synthesis inhibition with cycloheximide for 44 min slowed neither basal nor stretch-augmented ANP secretion but instead accelerated stretch-augmented secretion at low (but not at physiological) external Ca2+ concentration, suggesting that the constitutive component does not contribute substantially to either basal or stretch-augmented secretion. BFA, which disassembled Golgi cisternae, increased the stretch-augmented secretory rate via the regulated pathway and prevented Ca(2+)-dependent inactivation with time. Cellular ATP depletion rapidly and completely inhibited stretch-augmented secretion. We conclude that both basal and stretch-augmented utilize the energy-dependent regulated pathway, drawing on a large reservoir of concentrated prohormone stored in granules that is not detectably depleted during 44 min of stretch-augmented secretion at 37 degrees C.

Magnesium requirement for somatostatin inhibition of insulin secretion

1984 ◽  
Vol 105 (1) ◽  
pp. 83-86 ◽  
Author(s):  
Donald L. Curry ◽  
Leslie L. Bennett
Keyword(s):  
Insulin Secretion ◽  
Calcium Concentration ◽  
Inhibitory Effect ◽  
Secretory Process ◽  
Magnesium Ion ◽  
Second Phase ◽  
Intracellular Membrane ◽  
Calcium Magnesium ◽  
First Phase Insulin Secretion ◽  
Insulin Secretory Response

Abstract. Rat pancreas perfusions were performed using a perfusate with a fixed calcium concentration of 5 mEq/l and magnesium varying from 0 to 0.6 mEq/dl. Insulin secretion was stimulated by a constant glucose infusion of 300 mg/dl. This glucose concentration produces the typical biphasic insulin secretory response. We observed that in the absence of magnesium, somatostatin concentrations of 0.5 and 2.0 ng/ml were without effect on first phase insulin secretion. However, these same somatostatin levels produced 50% or more inhibition of insulin secretion in the presence of magnesium at 0.3 or 0.6 mEq/l. Similarly, in the absence of magnesium, somatostatin at 50 ng/ml failed to inhibit second phase insulin secretion, whereas this same somatostatin level produced about 50% inhibition of insulin secretion in the presence of magnesium at 0.3 mEq/l. Thus, altering perfusate magnesium concentrations without changing calcium is an important determinant of the degree of inhibition of secretion produced by somatostatin. In particular, in the absence of magnesium ion, somatostatin concentrations which would 'normally' produce 50% inhibition of secretion (ID50) are without effect. Therefore, magnesium ion is necessary for the full inhibitory effect of somatostatin to occur. These results suggest that inhibitors, as well as potentiators, of the insulin secretory process may act by altering intracellular/membrane calcium-magnesium ratios, but in opposite directions.

The secretory process in the Sheep's oviduct

1955 ◽  
Vol 121 (2) ◽  
pp. 187-205 ◽  
Author(s):  
Robert Hadek
Keyword(s):  
Secretory Process

scholarly journals Activation of stimulus-specific serine esterases (proteases) in the initiation of platelet secretion. I. Demonstration with organophosphorus inhibitors.

1976 ◽  
Vol 144 (6) ◽  
pp. 1657-1673 ◽  
Author(s):  
P M Henson ◽  
D Gould ◽  
E L Becker
Keyword(s):  
Serine Proteases ◽  
Platelet Activating Factor ◽  
Secretory Process ◽  
Subsequent Reaction ◽  
Irreversible Inhibitors ◽  
Activity Structure ◽  
Organophosphorus Inhibitors ◽  
Rabbit Platelets ◽  
Serine Esterases ◽  
Platelet Secretion

The effect of organophosphorus inhibitors of serine esterases (proteases) on secretion from washed rabbit platelets was examined. Five noncytotoxic stimuli were employed: collagen, thrombin, heterologous anti-platelet antibody (in the absence of complement), rabbit C3 bound to zymosan, and platelet activating factor derived from antigen-stimulated, IgE-sensitized rabbit basophils. Diisoprophyl phosphofluoridate, three series of p-nitrophenyl ethyl phosphonates, and a series of cyclohexyl phenylalkylphosphonofluridates were all found to be inhibitory to the platelet secretion. These are irreversible inhibitors of serine proteases but in this system were only inhibitory if added to the platelets concurrently with the stimuli. Pretreatment of either the platelets or the stimuli with the inhibitors followed by washing, was without effect on the subsequent reaction. This suggested the involvement of stimulus-activatable serine proteases in the secretory process. The concept was supported by finding that nonphosphorylating phosphonates or hydrolyzed phosphonates or phosphonofluoridates were without inhibitory action. The effect of a series of phosphonates or phosphonoflouridates in inhibiting each stimulus exhibited a unique activity-structure profile. The demonstration of such unique profiles with four series of inhibitors for each of the five stimuli was interpreted as demonstrating that a specific activatable serine protease was involved in the platelet secretory response to each stimulus.

scholarly journals THE INTRACELLULAR DISTRIBUTION OF GAMMA GLOBULIN IN A MOUSE PLASMA CELL TUMOR (X5563) AS REVEALED BY FLUORESCENCE AND ELECTRON MICROSCOPY

1962 ◽  
Vol 116 (4) ◽  
pp. 423-432 ◽  
Author(s):  
Richard A. Rifkind ◽  
Elliott F. Osserman ◽  
Konrad C. Hsu ◽  
Councilman Morgan
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Cell ◽  
Secretory Protein ◽  
Cell Tumor ◽  
Secretory Process ◽  
Cytoplasmic Matrix ◽  
Mouse Plasma ◽  
Plasma Cell Tumor ◽  
Antibody Staining ◽  
Fluorescence And Electron Microscopy

Ferritin- and fluorescein-conjugated antibody staining has been applied to a study of a mouse plasma cell tumor. The presence of myeloma globulin within cisternae of the endoplasmic reticulum was observed at a stage of the secretory process when the remainder of the cytoplasm was essentially free of labeled globulin. The distribution of ferritin suggested a functional heterogeneity among units of the endoplasmic reticulum. Apparently, progressive accumulation of globulin results in distension of the endoplasmic reticulum and, occasionally, in the appearance of considerable quantities of this secretory protein in the extracisternal cytoplasmic matrix. Participation of the Golgi apparatus in the packaging and release of small quantitites of globulin seems likely. In addition, however, fragmentation of the peripheral cytoplasm with rupture of distended ergastoplasmic vesicles appeared to be another pathway whereby globulin is secreted.

Electrophysiology of neurosecretory cells from the pituitary intermediate lobe

1988 ◽  
Vol 139 (1) ◽  
pp. 317-328
Author(s):  
R. N. McBurney ◽  
S. J. Kehl
Keyword(s):  
Cell Cultures ◽  
Calcium Ion ◽  
Action Potentials ◽  
Neurosecretory Cells ◽  
Secretory Process ◽  
High Threshold ◽  
Pars Intermedia ◽  
Low Threshold ◽  
Stimulus Secretion Coupling ◽  
Ca2 Channels

One of the goals in studying the electrical properties of neurosecretory cells is to relate their electrical activity to the process of secretion. A central question in these studies concerns the role of transmembrane calcium ion flux in the initiation of the secretory event. With regard to the secretory process in pituitary cells, several research groups have addressed this question in vitro using mixed primary anterior pituitary cell cultures or clonal cell lines derived from pituitary tumours. Other workers, including ourselves, have used homogeneous cell cultures derived from the pituitary intermediate lobes of rats to examine the characteristics of voltage-dependent conductances, the contribution of these conductances to action potentials and their role in stimulus-secretion coupling. Pars intermedia (PI) cells often fire spontaneous action potentials whose frequency can be modified by the injection of sustained currents through the recording electrode. In quiescent cells action potentials can also be evoked by the injection of depolarizing current stimuli. At around 20 degrees C these action potentials have a duration of about 5 ms. Although most of the inward current during action potentials is carried by sodium ions, a calcium ion component can be demonstrated under abnormal conditions. Voltage-clamp experiments have revealed that the membrane of these cells contains high-threshold, L-type, Ca2+ channels and low-threshold Ca2+ channels. Since hormone release from PI cells appears not to be dependent on action potential activity but does depend on external calcium ions, it is not clear what role these Ca2+ channels play in stimulus-secretion coupling in cells of the pituitary pars intermedia. One possibility is that the low-threshold Ca2+ channels are more important to the secretory process than the high-threshold channels.

Sodium Fluoride – a Stimulus for a Calcium-Triggered Secretory Process

1977 ◽  
Vol 55 (1-6) ◽  
pp. 193-200 ◽  
Author(s):  
S.A. Patkar ◽  
W. Kazimierczak ◽  
B. Diamant
Keyword(s):  
Sodium Fluoride ◽  
Secretory Process
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