scholarly journals THE BIOSYNTHESIS, INTRACELLULAR TRANSPORT, AND PACKAGING OF MELANOCYTE-STIMULATING PEPTIDES IN THE AMPHIBIAN PARS INTERMEDIA

1972 ◽  
Vol 53 (3) ◽  
pp. 642-653 ◽  
Author(s):  
C. R. Hopkins
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Intracellular Transport ◽  
Secretory Granules ◽  
Extended Period ◽  
Pars Intermedia ◽  
Secretory Product ◽  
Intracellular Location ◽  
Parenchymal Cells

Experiments in which glycine-3H has been introduced into excised neurointermediate lobes of Xenopus laevis incubated in a modified Krebs-Ringer bicarbonate medium have shown that ∼ 50% of the incorporated radioactivity is present in small peptides which have an electrophoretic mobility characteristic of the melanocyte-stimulating (MSH) peptides shown to be elaborated within the tissue. Based on these results and the demonstration that a discrete ∼ 7 min pulse of the label can be introduced into the tissue, electron microscope radioautography has been employed to follow the subcellular events concerned with the synthesis, intracellular transport, and packaging of the labeled secretory product. Together, these studies indicate that the newly synthesized material arises in peptide form, rather than as part of a larger prohormone molecule, on the ribosomes of the rough endoplasmic reticulum within the parenchymal cells of the intermediate portion of the lobe. A proportion is then incorporated into and remains for an extended period within the intracisternal granules which are a feature of the rough endoplasmic reticulum within these cells in vitro Most (∼ 60%) of the labeled secretory product, however, is transferred to the Golgi complex within 30 min and, within a further 10 min, becomes packaged into small (∼ 200 mµ) electron-opaque secretory granules. It is probable that under the conditions employed these granules represent the final intracellular location of secretory product before it is released

Modifications of pars intermedia cells of ovariectomized rats by oestrogen and progesterone

1986 ◽  
Vol 111 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Adriana Beatriz Ferreira ◽  
Maria Ester Celis
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Secretory Activity ◽  
Ovariectomized Rats ◽  
Ultrastructural Changes ◽  
Synthetic Activity ◽  
Pars Intermedia ◽  
Cytological Features ◽  
Electron Lucent

Abstract. The effects of the ovarian steroids, oestradiol benzoate (EB), and progesterone (P) on the cells of pars intermedia (PI) from chronically ovariectomized rats (CHR-OVX) were analyzed by qualitative and quantitative electron microscopy (EM) at different intervals after steroid injection. The PI cells of CHR-OVX are rich in secretory granules but poor in organelles related to hormonal synthesis. Twenty-four h after EB administration the cells exhibited cytological features indicative of an increased synthetic activity. These included hypertrophy of rough endoplasmic reticulum, cisternae, a moderately developed Golgi complex, and newly formed granules. These features were also observed in PI cells 48 h after EB administration. Thirty-two and 56 h after the treatment, the PI cells showed signs of both increased synthetic and secretory activity. Thus, it was possible to observe a well-developed rough endoplasmic reticulum, and Golgi apparatus, numerous electron-lucent vesicles, and secretory granules in contact with the cell membrane. However, no exocytotic figures were observed. Progesterone administration resulted in considerable modifications of the ultrastructural features of PI cells also indicative of increased synthetic and secretory activity. The greatest modifications were observed in the mornings with changes that were 12 h out of phase with respect to those observed with EB. Quantitative estimations of the variation in the content of secretory granules of PI cells fully confirmed the qualitative observations described above. The serum α-MSH concentrations in ovariectomized rats was found to be incresed 24 h after administration of a single dose of EB and thereafter serum MSH exhibited high levels in the afternoon, whereas the values in the morming were lower. In spayed rats, progesterone injection also resulted in an increase of the serum MSH concentration, but with high levels in the mornings and low levels in the afternoons. In conclusion, EB and P induce modifications in the levels of α-MSH as well as in the ultrastructural changes of the PI cells.

Zwischenzelladenom der Hypophyse mit «Cushing-ähnlicher» Symptomatologie beim Pferd

1974 ◽  
Vol 11 (5) ◽  
pp. 417-429 ◽  
Author(s):  
B. U. Pauli ◽  
G. L. Rossi ◽  
R. Straub
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Tumor Cells ◽  
Adrenal Cortex ◽  
Rough Endoplasmic Reticulum ◽  
Cushing’S Disease ◽  
Pituitary Tumor ◽  
Secretory Granules ◽  
Cushing's Disease ◽  
Pars Intermedia

A trabecular adenoma of the pars intermedia of the hypophysis was seen in a 13-year-old half-bred mare that presented symptoms corresponding to Cushing's disease of man. The spindle-shaped tumor cells were for the most part ‘light’, seldom ‘dark’. Both of them were characterized by well-developed rough endoplasmic reticulum, small Golgi apparatus, and typical secretory granules with a diameter of about 200 μm. The pituitary tumor and the symptoms were accompanied by increased plasma adenocorticotrophic hormone (ACTH) and by bilateral hyperplasia of the adrenal cortex. The tumor cells of the pars intermedia were probably the source of increased ACTH, and the hyperplasia of the adrenal cortex was probably responsible for the symptoms of Cushing's disease.

scholarly journals DEVELOPMENT OF ENDOGENOUS PEROXIDASE IN FETAL RAT SUBMANDIBULAR GLAND

1973 ◽  
Vol 21 (1) ◽  
pp. 42-50 ◽  
Author(s):  
SHOHEI YAMASHINA ◽  
TIBOR BARKA
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Submandibular Gland ◽  
Rough Endoplasmic Reticulum ◽  
Peroxidase Activity ◽  
Secretory Granules ◽  
Prenatal Development ◽  
Reaction Products ◽  
Cell Type ◽  
Endogenous Peroxidase

The prenatal development of endogenous peroxidase activity in the submandibular gland of rat was investigated by means of the diaminobenzidine-H2O2 histochemical method. The submandibular gland of a 16-day-old fetus was composed of cords of uniform, undifferentiated cells which contained no secretory granules and revealed no peroxidase activity. Peroxidase activity first appeared at the 17th day of gestation in the cisternae of the rough endoplasmic reticulum and nuclear envelope in a few cells. At the 18th day of gestation cells which exhibited reaction products in the rough endoplasmic reticulum and nuclear envelope also contained secretory granules with a strong peroxidase activity. During the last days of gestation the number of peroxidase positive cells, which contained numerous secretory granules, increased. The peroxidase-containing cells are the immediate precursors of the proacinar cells of early postnatal stages. During the same time period, when the peroxidase-containing cells differentiated, a second cell type also differentiated in the cellular cords. The development of this cell type was marked by the appearance of secretory granules stainable with toluidine blue. Through the prenatal development, this cell type revealed no peroxidase activity and was identified with the terminal tubule cell of the newborn. The morphologic and cytochemical findings indicate that terminal tubule cells and proacinar cells are committed cells; the former differentiate toward 2nd order intercalated duct cells and the latter transform to mature acinar cells.

scholarly journals THE ELABORATION OF PROTEIN AND CARBOHYDRATE BY RAT PARATHYROID CELLS AS REVEALED BY ELECTRON MICROSCOPE RADIOAUTOGRAPHY

1971 ◽  
Vol 51 (3) ◽  
pp. 596-610 ◽  
Author(s):  
K. Nakagami ◽  
H. Warshawsky ◽  
C. P. Leblond
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Intravenous Injection ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Glycoprotein Precursor ◽  
Secretion Granules ◽  
And Migration ◽  
The One ◽  
Membrane Cell

The parathyroid glands of young rats were radioautographed after a single injection of the protein precursor tyrosine-3H in the hope of identifying the sites of synthesis and migration of newly formed protein in the gland cells. The same procedure was used after injection of the glycoprotein precursor galactose-3H. As early as 2 min after intravenous injection of tyrosine-3H, the label was mainly found in the rough endoplasmic reticulum suggesting that cisternal ribosomes are sites of protein synthesis. By 5 and 10 min, much of the label had migrated from the rough endoplasmic reticulum into the Golgi apparatus. By 20 and 30 min, some label had migrated from there into secretory granules. By 45 min and 1 hr, the label content of the cell had decreased, indicating release of labeled material outside the cell. At 2 min after intravenous injection of galactose-3H, the label was mainly present in the Golgi apparatus, where presumably galactose is taken up into glycoprotein. By 10 min, some label appeared in secretion granules and by 30 min release of the material to the outside of the cell was under way. In conclusion, it is likely that the tyrosine-labeled protein material consists mainly of the parathyroid hormone. The galactose-labeled carbohydrate material would be either associated with the hormone in the cell or be part of a distinct glycoprotein which may be the one present on the outer surface of the plasma membrane (cell coat).

Altered labelling of the cell surface and intracellular organelles with [3H]mannose in enucleated amoebae

1984 ◽  
Vol 68 (1) ◽  
pp. 83-94
Author(s):  
C.J. Flickinger
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Rough Endoplasmic Reticulum ◽  
Intracellular Transport ◽  
Cell Organelles ◽  
Intracellular Organelles ◽  
And Control ◽  
Kinetics Of ◽  
Heavy Labelling

The production, transport, and disposition of material labelled with [3H]mannose were studied in microsurgically enucleated and control amoebae. Cells were injected with the precursor and samples were prepared for electron-microscope radioautography at intervals, up to 24 h later. Control cells showed heavy labelling of the rough endoplasmic reticulum and the Golgi apparatus at early intervals after injection. Later, labelling of groups of small vesicles increased, and the percentage of grains over the cell surface peaked 12 h after administration of the precursor. Two major changes were detected in enucleate amoebae. First, the kinetics of labelling of cell organelles with [3H]mannose were altered in the absence of the nucleus. The Golgi apparatus and cell surface both displayed maximal labelling at later intervals in enucleates, and the percentage of grains over the rough endoplasmic reticulum varied less with time in enucleated than in control cells. Second, the distribution of radioactivity was altered. A greater percentage of grains was associated with lysosomes in enucleates than in control cells. The change in the kinetics of labelling of the endoplasmic reticulum, Golgi apparatus and cell surface indicates that intracellular transport of surface material was slower in the absence of the nucleus. It is suggested that this is related to the decreased motility of enucleate cells.

scholarly journals ULTRASTRUCTURAL VARIATIONS IN N,N'-BIS(4-AMINOPHENYL)-N,N'-DIMETHYLETHYLENEDIAMINE (BED) OXIDASE LOCALIZATION IN RAT LIVER AND PAROTID GLAND WITH VARIATION IN LENGTH OF FIXATION

1972 ◽  
Vol 20 (12) ◽  
pp. 1024-1030 ◽  
Author(s):  
W. ALLEN SHANNON ◽  
ARNOLD M. SELIGMAN
Keyword(s):  
Endoplasmic Reticulum ◽  
Parotid Gland ◽  
Rat Liver ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Terminal Oxidase ◽  
Outer Compartment ◽  
Fixation Reaction

The localization and reactivity of a terminal oxidase which oxidizes N,N'-bis(4-amino-phenyl)-N,N'-dimethylethylenediamine (BED) were studied in rat liver and parotid gland after varying the concentration of formaldehyde fixative and the length of fixation. Reaction product was observed in mitochondrial outer compartments, smooth elements of rough endoplasmic reticulum, some Golgi lamellae, perinuclear membranes and cytoplasmic membranous structures often associated with mitochondria. A reaction also occurred in the limiting membrane and, to some degree, in the material comprising the secretory granules of the parotid. The reaction in the mitochondrial outer compartment was extremely formaldehyde-sensitive. Controls in which diaminobenzidine (DAB) was substituted for BED showed reaction only in mitochondrial cristae and outer compartments, whereas controls without either reagent showed no reactivity.

scholarly journals LECITHIN SYNTHESIS, INTRACELLULAR TRANSPORT, AND SECRETION IN RAT LIVER

1969 ◽  
Vol 40 (2) ◽  
pp. 461-483 ◽  
Author(s):  
Olga Stein ◽  
Yechezkiel Stein
Keyword(s):  
Endoplasmic Reticulum ◽  
Liver Cell ◽  
Phosphatidyl Choline ◽  
Intracellular Transport ◽  
Phosphatidyl Ethanolamine ◽  
Specific Activity ◽  
Perfused Liver ◽  
Precursor Pool

Injection of choline-3H into choline-deficient rats resulted in an enhanced incorporation of the label into liver lecithin, as compared to the incorporation of label into liver lecithin of normal rats. The results obtained with the use of different lecithin precursors indicate that in the intact liver cell, both in vivo and in vitro, exchange of choline with phosphatidyl-choline is not significant. The synthesis and secretion of lecithins by the choline-deficient liver compare favorably with the liver of choline-supplemented rats, when both are presented with labeled choline or lysolecithin as lecithin precursors. Radioautography of the choline-deficient liver shows that 5 min after injection of choline-3H the newly synthesized lecithin is found in the endoplasmic reticulum (62%), mitochondria (13%), and at the "cell boundary" (20%). The ratio of the specific activity of microsomal and mitochondrial lecithin, labeled with choline, glycerol, or linoleate, was 1.53 at 5 min after injection, but the ratio of the specific activity of phosphatidyl ethanolamine (PE), labeled with ethanolamine, was 5.3. These results indicate that lecithin and PE are synthesized mainly in the endoplasmic reticulum, and are transferred into mitochondria at different rates. The site of a precursor pool of bile lecithin was studied in the intact rat and in the perfused liver. Following labeling with choline-3H, microsomal lecithin isolated from perfused liver had a specific activity lower than that of bile lecithin, but the specific activity of microsomal linoleyl lecithin was comparable to that of bile lecithin between 30 and 90 min of perfusion. It is proposed that the site of the bile lecithin pool is located in the endoplasmic reticulum and that the pool consists mostly of linoleyl lecithin.

scholarly journals RADIOAUTOGRAPHIC VISUALIZATION OF THE INCORPORATION OF GALACTOSE-3H AND MANNOSE-3H BY RAT THYROIDS IN VITRO IN RELATION TO THE STAGES OF THYROGLOBULIN SYNTHESIS

1969 ◽  
Vol 43 (2) ◽  
pp. 289-311 ◽  
Author(s):  
P. Whur ◽  
Annette Herscovics ◽  
C. P. Leblond
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Golgi Apparatus ◽  
Rough Endoplasmic Reticulum ◽  
Light Microscope ◽  
Detectable Effect ◽  
Apical Vesicles ◽  
Rat Thyroid

Rat thyroid lobes incubated with mannose-3H, galactose-3H, or leucine-3H, were studied by radioautography. With leucine-3H and mannose-3H, the grain reaction observed in the light microscope is distributed diffusely over the cells at 5 min, with no reaction over the colloid. Later, the grains are concentrated towards the apex, and colloid reactions begin to appear by 2 hr. With galactose-3H, the reaction at 5 min is again restricted to the cells but it consists of clumped grains next to the nucleus. Soon after, grains are concentrated at the cell apex and colloid reactions appear in some follicles as early as 30 min. Puromycin almost totally inhibits incorporation of leucine-3H and mannose-3H, but has no detectable effect on galactose-3H incorporation during the 1st hr. Quantitation of electron microscope radioautographs shows that mannose-3H label localizes initially in the rough endoplasmic reticulum, and by 1–2 hr much of this reaction is transferred to the Golgi apparatus. At 3 hr and subsequently, significant reactions are present over apical vesicles and colloid, while the Golgi reaction declines. Label associated with galactose-3H localizes initially in the Golgi apparatus and rapidly transfers to the apical vesicles, and then to the colloid. These findings indicate that mannose incorporation into thyroglobulin precursors occurs within the rough endoplasmic reticulum; these precursors then migrate to the Golgi apparatus, where galactose incorporation takes place. The glycoprotein thus formed migrates via the apical vesicles to the colloid.

The biosynthesis of cytochrome P450 by rough endoplasmic reticulum in vitro

FEBS Letters ◽  
1979 ◽  
Vol 98 (2) ◽  
pp. 403-407 ◽  
Author(s):  
John A. Craft ◽  
Michael B. Cooper ◽  
Margaret R. Estall ◽  
Brian R. Rabin
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome P450 ◽  
Rough Endoplasmic Reticulum

scholarly journals SYNTHESIS, INTRACELLULAR TRANSPORT, AND DISCHARGE OF SECRETORY PROTEINS IN STIMULATED PANCREATIC EXOCRINE CELLS

1971 ◽  
Vol 50 (1) ◽  
pp. 135-158 ◽  
Author(s):  
James D. Jamieson ◽  
George E. Palade
Keyword(s):  
Protein Synthesis ◽  
Golgi Complex ◽  
Intracellular Transport ◽  
Secretory Proteins ◽  
Cell Fractionation ◽  
Secretory Product ◽  
Zymogen Granules ◽  
Pancreatic Exocrine ◽  
Storage Granules

Our previous observations on the synthesis and transport of secretory proteins in the pancreatic exocrine cell were made on pancreatic slices from starved guinea pigs and accordingly apply to the resting, unstimulated cell. Normally, however, the gland functions in cycles during which zymogen granules accumulate in the cell and are subsequently discharged from it in response to secretogogues. The present experiments were undertaken to determine if secretory stimuli applied in vitro result in adjustments in the rates of protein synthesis and/or of intracellular transport. To this intent pancreatic slices from starved animals were stimulated in vitro for 3 hr with 0.01 mM carbamylcholine. During the first hour of treatment the acinar lumen profile is markedly enlarged due to insertion of zymogen granule membranes into the apical plasmalemma accompanying exocytosis of the granule content. Between 2 and 3 hr of stimulation the luminal profile reverts to unstimulated dimensions while depletion of the granule population nears completion. The acinar cells in 3-hr stimulated slices are characterized by the virtual complete absence of typical condensing vacuoles and zymogen granules, contain a markedly enlarged Golgi complex consisting of numerous stacked cisternae and electron-opaque vesicles, and possess many small pleomorphic storage granules. Slices in this condition were pulse labeled with leucine-3H and the route and timetable of intracellular transport assessed during chase incubation by cell fractionation, electron microscope radioautography, and a discharge assay covering the entire secretory pathway. The results showed that the rate of protein synthesis, the rate of drainage of the rough-surfaced endoplasmic reticulum (RER) compartment, and the over-all transit time of secretory proteins through the cells was not accelerated by the secretogogue. Secretory stimulation did not lead to a rerouting of secretory proteins through the cell sap. In the resting cell, the secretory product is concentrated in condensing vacuoles and stored as a relatively homogeneous population of spherical zymogen granules. By contrast, in the stimulated cell, secretory proteins are initially concentrated in the flattened saccules of the enlarged Golgi complex and subsequently stored in numerous small storage granules before release. The results suggest that secretory stimuli applied in vitro primarily affect the discharge of secretory proteins and do not, directly or indirectly, influence their rates of synthesis and intracellular transport.

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