scholarly journals Phospholipide Turnover in Microsomal Membranes of the Pancreas during Enzyme Secretion

1959 ◽  
Vol 6 (2) ◽  
pp. 207-214 ◽  
Author(s):  
Colvin M. Redman ◽  
Lowell E. Hokin
Keyword(s):  
Soluble Fraction ◽  
Cellular Component ◽  
Enzyme Secretion ◽  
Zymogen Granules ◽  
Membranous Structure ◽  
Microsomal Membranes ◽  
Microsome Fraction ◽  
The Individual ◽  
Soluble Components ◽  
Stimulation Of

After incubation of pigeon pancreas slices with P32 and isolation of various fractions by differential centrifugation the deoxycholate extract of the microsome fraction was found to account for over half of the phospholipide P and over half of the P32 incorporated into the phospholipides. The remaining phospholipide P and P32 were fairly evenly distributed in the nuclei, zymogen granules, mitochondria, microsomal ribonucleoprotein particles, and the soluble fraction. When enzyme secretion was stimulated with acetylcholine about two-thirds of the increment in radioactivity in the total phospholipides was found in deoxycholate soluble components of the microsome fraction. The remainder of the increment was distributed in the other fractions. This indicates that the cellular component in which the increase in phospholipide turnover occurs on stimulation of secretion is a membranous structure. Evidence is presented which indicates that the increment in radioactivity in the non-microsomal fractions on stimulation of secretion is due to contamination of these fractions with fragments of the stimulated membranous structure. The distribution of P32 radioactivity in each of the chromatographically separated phospholipides in the various fractions from unstimulated tissue paralleled the distribution of radioactivity in the total phospholipide fraction, indicating that individual phospholipides are not concentrated in different fractions but are associated together in the membranous structures of the microsome fraction. The major proportion of the stimulation of the turnover of the individual phospholipides also occurred in the microsome fraction. The distribution of radioactivity from glycerol-1-C14 in the total phospholipides and in the individual phospholipides in the various fractions was similar to the distribution of P32. In the microsome fraction acetylcholine stimulated the incorporation of glycerol-1-C14 in each phospholipide which showed a stimulation of P32 incorporation. The significance of the turnover of phosphatides in microsomal membranes in relation to the mechanism of secretion is discussed.

scholarly journals IN VITRO STIMULATION OF ENZYME SECRETION AND THE SYNTHESIS OF MICROSOMAL MEMBRANES IN THE PANCREAS OF THE GUINEA PIG

1971 ◽  
Vol 51 (2) ◽  
pp. 396-404 ◽  
Author(s):  
Jacopo Meldolesi ◽  
Dario Cova
Keyword(s):  
Guinea Pig ◽  
High Ionic Strength ◽  
Enzyme Secretion ◽  
Secretory Cells ◽  
Secretory Cycle ◽  
Golgi Membranes ◽  
Granule Membrane ◽  
Microsomal Membranes ◽  
Stimulation Of

Several mechanisms have been suggested to explain how secretory cells remove from the plasmalemma the excess membrane resulting from the insertion of granule membrane during exocytosis: intact patches of membrane may be internalized and then reutilized within the cell; alternatively these membranes may be either disassembled to subunits or degraded. In the latter case new membranes should be synthetized at other sites of the cell, probably in the rough-surfaced endoplasmic reticulum (RER) and the Golgi complex. In the present research, membrane subfractions were obtained from rough microsomes (derived from fragmented and resealed RER cisternae) and from smooth microsomes (primarily contributed by Golgi stacks and vesicles) of the guinea pig pancreas by incubation at 4°C for 4 hr in 0.0005 M puromycin at high ionic strength followed by mild (pH 7.8) alkaline extraction with 0.2 M NaHCO3. Such treatments release the majority of nonmembrane components of both microsomal fractions (i.e., contained secretory enzymes, ribosomes, and absorbed proteins of the cell sap) and allow the membranes to be recovered by centrifugation. The effect of in vitro stimulation of enzyme secretion (brought about in pancreas slices by 0.0001 M carbamoyl choline) on the rate of synthesis of the phospholipid (PLP) and protein of these membranes was then investigated. In agreement with previous data, we observed that in stimulated slices the synthesis of microsomal PLP was greatly increased. In contrast, the synthesis of microsomal membrane proteins was unchanged. These results suggest that exocytosis is not coupled with an increased rate of synthesis of complete ER and Golgi membranes and are, therefore, consistent with the view that excess plasma membrane is preserved and reutilized, either as discrete membrane patches or as membrane macromolecules, throughout the secretory cycle.

scholarly journals THE EFFECTS OF SECRETAGOGUES ON THE INCORPORATION OF [2-3H]MYOINOSITOL INTO LIPID IN CYTOLOGICAL FRACTIONS IN THE PANCREAS OF THE GUINEA PIG IN VIVO

1973 ◽  
Vol 56 (3) ◽  
pp. 736-745 ◽  
Author(s):  
Dorothy Gerber ◽  
Margaret Davies ◽  
Lowell E. Hokin
Keyword(s):  
Endoplasmic Reticulum ◽  
Single Injection ◽  
Enzyme Secretion ◽  
Amylase Level ◽  
Membrane Flow ◽  
Secretory Cycle ◽  
Microsome Fraction ◽  
Stimulation Of ◽  
Cholinergic Drug

Stimulation of enzyme secretion in the pancreas on injection of a single dose of the cholinergic drug, pilocarpine, was associated with an increased incorporation of [2-3H]myoinositol into a lipid, which was previously characterized as phosphatidylinositol. Stimulation of enzyme secretion by hourly injection of the pancreozymin congener, caerulein, led to more increased phosphatidylinositol synthesis than with a single injection of pilocarpine. The amylase level of the pancreas remained at a low level as long as caerulein was injected, indicating continued stimulation of enzyme secretion even though increased phosphatidylinositol synthesis ceased after 6 h. Feeding gave the same stimulation of phosphatidylinositol synthesis as caerulein. The major synthesis of phosphatidylinositol in controls and the stimulation of phosphatidylinositol synthesis by pilocarpine was entirely confined to the microsome fraction throughout the experiments (up to 18 h). This shows that there is no flow of microsomal membrane (smooth- or rough-surfaced endoplasmic reticulum) to other membranous structures throughout the secretory cycle and beyond. It is concluded that the stimulation of phosphatidylinositol synthesis by pancreatic secretagogues is confined to microsomal elements and does not play any role in membrane flow.

Secretagogue-induced changes in subcellular Ca2+ distribution in isolated pancreatic acini

1981 ◽  
Vol 240 (2) ◽  
pp. G130-G140
Author(s):  
R. L. Dormer ◽  
J. A. Williams
Keyword(s):  
Atomic Absorption Spectrometry ◽  
High Speed ◽  
Microsomal Fraction ◽  
Absorption Spectrometry ◽  
Subcellular Fractionation ◽  
Differential Centrifugation ◽  
Zymogen Granules ◽  
Pancreatic Acini ◽  
Induced Changes ◽  
Stimulation Of

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

Vanadate Stimulation of Pyridine Nucleotide Oxidation in Mammalian Liver Microsomal Membranes

1988 ◽  
pp. 777-780
Author(s):  
Roger A. Coulombe ◽  
David W. Reif ◽  
Randal J. Keller ◽  
Donald P. Briskin ◽  
Steven D. Aust ◽  
...  
Keyword(s):  
Pyridine Nucleotide ◽  
Mammalian Liver ◽  
Microsomal Membranes ◽  
Pyridine Nucleotide Oxidation ◽  
Stimulation Of

Cholecystokinin-induced desensitization of enzyme secretion in dispersed acini from guinea pig pancreas

1980 ◽  
Vol 239 (4) ◽  
pp. G272-G279 ◽  
Author(s):  
S. Abdelmoumene ◽  
J. D. Gardner
Keyword(s):  
Guinea Pig ◽  
Vasoactive Intestinal Peptide ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Temperature Dependent ◽  
Cellular Calcium ◽  
Maximal Stimulation ◽  
Stimulation Of

Incubating dispersed acini from guinea pig pancreas with cholecystokinin and then washing the cells to remove cholecystokinin reduced the subsequent stimulation of amylase secretion caused by pancreatic secretagogues, whose actions are mediated by release of cellular calcium (i.e., cholecystokinin, carbamylcholine, bombesin, litorin, physalaemin, and A23187), but did not alter the stimulation caused by secretagogues whose actions are mediated by cAMP (i.e., vasoactive intestinal peptide and secretin). This cholecystokinin-induced desensitization was reversible, and the onset of the process as well as its reversal were time- and temperature-dependent changes. The concentrations of cholecystokinin required to cause desensitization were greater than those required to cause maximal stimulation of amylase secretion, and this finding suggests that the submaximal stimulation of enzyme secretion seen with supramaximal concentrations of cholecystokinin may be caused by cholecystokinin-induced desensitization.

scholarly journals The formation, distribution and function of ribosomes and microsomal membranes during induced amphibian metamorphosis

1967 ◽  
Vol 105 (2) ◽  
pp. 783-801 ◽  
Author(s):  
J. R. Tata
Keyword(s):  
Endoplasmic Reticulum ◽  
Ribosomal Proteins ◽  
Specific Activity ◽  
Tail Length ◽  
Similar Response ◽  
Carbamoyl Phosphate ◽  
Microsomal Membranes ◽  
Stimulation Of ◽  
Induction Of Metamorphosis

1. A lag period of about 4 days preceded the onset of metamorphosis precociously induced by tri-iodothyronine in tadpoles of the giant American bullfrog (Rana catesbeiana). It was established by the accelerated synthesis or induction of carbamoyl phosphate synthetase and cytochrome oxidase in the liver, serum albumin and adult haemoglobin in the blood, acid phosphatase in the tail, and the increase in the hindleg/tail length ratio. 2. A 4- to 6-fold stimulation, 2 days after the induction of metamorphosis, of the rate of synthesis of rapidly labelled nuclear RNA in liver cells was followed by an increasing amount of RNA appearing in the cytoplasm. Most of the newly formed RNA on induction of metamorphosis was of the ribosomal type. An accelerated turnover at early stages of development preceded a net accumulation of RNA in the cytoplasm, with no change in the amount of DNA per liver. 3. Most hepatic ribosomes of the pre-metamorphic tadpoles were present as 78s monomers and 100s dimers; metamorphosis caused a shift towards larger polysomal aggregates with newly formed ribosomes that were relatively more tightly bound to membranes of the endoplasmic reticulum. 4. The appearance of new polyribosomes in the cytoplasm on induction of metamorphosis was co-ordinated in time with a stimulation of synthesis of phospholipids of the smooth and rough endoplasmic reticulum, followed by a gradual shift in preponderance from the smooth to the rough type of microsomal membranes. 5. Electron- and optical-microscopic examination of intact hepatocytes revealed a striking change in the distribution and nature of ribosomes and microsomal membranes during metamorphosis. 6. Ribosomes prepared from non-metamorphosing and metamorphosing animals were identical in their sedimentation coefficients and in the structural ribosomal proteins. The base composition and sedimentation coefficients of ribosomal RNA were also identical. Induction of metamorphosis also did not alter the incorporation of 32P into the different phospholipid constituents of microsomal membranes. 7. Nascent 14C-labelled protein with the highest specific activity was recovered in the ‘heavy’ rough membrane fraction of microsomes, whereas little 14C was associated with ‘free’ polysomes. Protein synthesis in vivo was most markedly stimulated during metamorphosis in the tightly membrane-bound ribosomal fraction after the appearance of new ribosomes. 8. The rate of synthesis of macromolecules in vivo could not be followed beyond 7–8 days after induction because of variable shifts in precursor pools due to regression of larval tissues. 9. The stimulation of RNA and ribosome formation was specifically associated with the process of metamorphosis since no similar response to thyroid hormones occurred in those species (Axolotl and Necturus) in which the hormones failed to induce metamorphosis.

Memoirs: The Neuro-Muscular Mechanism of the Gill of Pecten

1930 ◽  
Vol s2-73 (291) ◽  
pp. 365-392
Author(s):  
S. B. SETNA
Keyword(s):  
Feeding Habits ◽  
Adductor Muscle ◽  
The Body ◽  
Muscle Fibres ◽  
Direct Stimulation ◽  
Gill Filaments ◽  
Lateral Extent ◽  
Branchial Nerve ◽  
The Individual ◽  
Stimulation Of

Experimental. 1. The contraction of the adductor-muscle which follows stimulation of the palial nerve is preceded by a marked contraction of the ctenidial axis, so that the gill contracts before the adductor-muscle becomes active. This movement of the ctenidium is abolished if the main branchial nerve is cut near its origin. 2. The gills of Pecten possess a neuromuscular mechanism which is to some extent independent of the rest of the body, so that excised gills when stimulated react in the same way as an attached gill. 3. The lamellae of the gill possess two distinct types of movement. (a) When the surface of the gill is stimulated by contact with a glass rod or by carmine particles, the frontal surfaces of the two lamellae approach each other; the movement very often being executed by the lamella which is not actually being stimulated. The lateral extent of these movements (concertina movements) is roughly proportional to the intensity of the stimulus. Such movements normally appear to transfer the bulk of the material on to the mantle. Separation of the main branchial nerve abolishes these movements. (b) Each principal filament is capable of moving the ordinary filaments to which it is attached. This movement (flapping movement) is due to the movements of the interfilamentar junctions which alternatively move up and down at right angles to their length. This motion is independent of the branchial nerve and can be produced by direct stimulation of very tiny pieces of the individual filaments. 4. The significance of gill movements to feeding habits is discussed. The course of food particles depends on the nature of the stimuli affecting the gill. Histological. 5. The ctenidial axis and the principal filaments have a stratum of anastomosing nerve-cells which appear to form a true nerve-net comparable to that of the mantle. 6. The gill receives nerve-fibres from two sources, the brain and the visceral ganglion. The subsidiary branchial nerve is a structure hitherto unknown in the molluscan gill; so far its function is unknown. Each gill has four main longitudinal nerve-trunks. 7. The osphradium of the gill has a much more extensive distribution than has hitherto been supposed. 8. Two sets of muscles exist at the base of the gill-filaments, and these are responsible for movements of the lamellae. The muscle-fibres are non-striated. 9. The principal filaments are connected to the ordinary filaments by processes containing true muscle-cells, and by these cells movements of the filaments are effected.

Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct

1989 ◽  
Vol 257 (1) ◽  
pp. C94-C101 ◽  
Author(s):  
K. Matsuzaki ◽  
J. B. Stokes ◽  
V. L. Schuster
Keyword(s):  
Anion Exchange ◽  
Intracellular Ph ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
High K ◽  
Shift Experiment ◽  
Ethanesulfonic Acid ◽  
The Individual ◽  
Stimulation Of

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, KCl (nm/s); a small fraction is effected by Cl--HCO3- exchange and Cl- diffusion. We previously reported that changing from a CO2-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) bath to a 5% CO2-25 mM HCO3- bath stimulates Cl- self exchange. Here, we examine in further detail the individual components of the CO2-HCO3- system that stimulate KCl. Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated KCl by 70 +/- 19 nm/s, a delta KCl comparable to that induced by 1% CO2 (pH 7.12), 6% CO2 (pH 6.6), or 6% CO2-25 mM HCO3- (pH 7.4). The roles of intracellular pH (pHi) and HCO3- concentration were examined by clamping pHi using high K+ and nigericin. Increasing pHi from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased KCl by 71 +/- 17 nm/s. These results suggest that pHi might regulate anion exchange. However, during such a pHi-shift experiment, metabolically derived CO2 produces a concomitant change in intracellular HCO3- concentration [( HCO3-]i). To determine whether an increase in [HCO3-]i could stimulate Cl- self exchange, we replaced HEPES with 6% CO2-5 mM HCO3- isohydrically (pHi clamped at 6.9). With this increase in [HCO3-]i at constant pHi, KCl increased by 51 +/- 10 nm/s. These maneuvers had negligible effects on Cl- diffusion and Cl--HCO3- exchange. These experiments demonstrate that increases in cell [HCO3-] (or perhaps CO2) can stimulate transepithelial anion exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Organizational Creativity Management: Discussion Elements

2018 ◽  
Vol 22 (6) ◽  
pp. 922-939 ◽  
Author(s):  
Henrique Muzzio ◽  
Fernando Gomes Paiva Júnior
Keyword(s):  
Theoretical Concept ◽  
Work Relationships ◽  
Social Phenomenon ◽  
Creative Processes ◽  
Organizational Creativity ◽  
Creative Leadership ◽  
Managerial Grid ◽  
The Individual ◽  
Over Time ◽  
Stimulation Of

Abstract This article proposes to work with the theoretical concept of creativity management by promoting a reflection defined by encouraging work relationships that involve creative individuals and creative leadership in attitudes that foster a creative culture. This analysis considers creativity as a precursor of innovation and evaluates it as a universe capable of improving organizational competitiveness, since, creativity is understood as a social phenomenon. The discussion in this article addresses conditions and characteristics related to the individual, to leadership and culture. Creativity management is a component of a managerial grid focused on interfering in the internal and external contexts of an organization by reviewing deviant and divergent practices regarding the stimulation of creative processes. The development of creativity over time is illustrated by a concept called the spiral of creativity. In conclusion, analyzing creativity as something that is collectively produced and has manageable elements increases the ability to make decisions that foster creativity and allow it to be managed collectively.

Soft Palate Reflex: Technical Requirements and First Results

1992 ◽  
Vol 29 (4) ◽  
pp. 340-345 ◽  
Author(s):  
Godber S. Godbersen ◽  
Johannes Schneider-Littfeld ◽  
Jochen A. Werner ◽  
Sönke Wolters ◽  
Axel Pellner
Keyword(s):  
Soft Palate ◽  
Healthy Subjects ◽  
Processing System ◽  
Data Processing System ◽  
Response Latencies ◽  
Technical Requirements ◽  
First Results ◽  
The Individual ◽  
Electromyographic Signals ◽  
Stimulation Of

The present study describes technical prerequisites for soft palate reflex measurements and first results. Reflex measurements can be done using standard electromyographic methods. The data-processing system that records and processes the electromyographic signals was activated when the soft palate was stimulated by a newly developed device. The first results of objective soft palate reflex measurements in 15 healthy subjects show that the musculus levator veli palatini reacts to a mechanical stimulation of the soft palate with a contraction that can be measured electromyographicslly. The response latencies were constant in the individual subjects. In 12 subjects a minimum of 30 ms and a maximum of 61 ms was recorded. In one healthy subject, the reflex was activated only after 167 ms. No reflex could be evoked in two subjects. The stimulus was always supraliminal. Reaction time was longer following surface anesthesia of the oral mucosa.

Sign in / Sign up

Export Citation Format

Share Document