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Results for “Endoplasmic Reticulum”

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At least 19 recordsLinked to original sources

PubMed1977

Two fractions of rough endoplasmic reticulum from rat liver. I. Recovery of rapidly sedimenting endoplasmic reticulum in association with mitochondria.

Low-speed centrifugation (640 g) of rat liver homogenates, prepared with a standard ionic medium, yielded a pellet from which a rapidly sedimenting fraction of rough endoplasmic reticulum (RSER) was recovered free of nuclei. This fraction contained 20-25% of cellular RNA and approximately 30% of total glucose-6-phosphatase (ER marker) activity. A major portion of total cytochrome c oxidase (mitochondrial marker) activity was also recovered in this fraction, with the remainder sedimenting between 640 and 6,000 g. Evidence is provided which indicates that RSER may be intimately associated with mitochondria. Complete dissociation of ER from mitochondria in the RSER fraction required very harsh conditions. Sucrose density gradient centrifugation analysis revealed that 95% dissociation could be achieved when the RSER fraction was first resuspended in buffer containing 500 mM KCl and 20 mM EDTA, and subjected to shearing. Excluding KCl, EDTA, or shearing from the procedure resulted in incomplete separation. Both electron microscopy and marker enzyme analysis of mitochondria purified by this procedure indicated that some structural damage and leakage of proteins from matrix and intermembrane compartments had occurred. Nevertheless, when mitochondria from RSER and postnuclear 6,000-g pellet fractions were purified in this way fromanimals injected with [35S]methionine +/- cycloheximide, mitochondria from the postnuclear 6,000-g pellet were found to incorporate approximately two times more cytoplasmically synthesized radioactive protein per milligram mitochondrial protein (or per unit cytochrome c oxidase activity) than did mitochondria from the RSER fraction. Mitochondria-RSER associations, therefore, do not appear to facilitate enhanced incorporation of mitochondrial proteins which are newly synthesized in the cytoplasm.

Animals↗

PubMed1977

Biogenesis of endoplasmic reticulum membrane in rat liver cells. II. Discharge of the nascent peptides of NADPH-cytochrome c reductase and cytochrome b5 on the cytoplasmic side of the endoplasmic reticulum membrane.

The direction of discharge of the nascent peptides of NADPH-cytochrome c reductase and cytochrome b5 from bound polyribosomes of rough microsomes was investigated in order to elucidate the mechanism of separation of these membrane proteins from secretory proteins, which are also synthesized by the same class of ribosomes of rough endoplasmic reticulum. The nascent peptides of NADPH-cytochrome c reductase and cytochrome b5 in intact rough microsomes were accessible to externally added 125I-Fab's against these proteins, and were susceptible to trypsin digestion, whereas the nascent peptides of serum albumin were not. The nascent peptides of these two microsomal proteins were released into the cytoplasm by puromycin treatment of intact rough microsomes, while the nascent peptides of serum albumin were retained in the microsomal lumen. These observations suggest that the nascent peptides of microsomal proteins, which are present on the cytoplasmic surface of the endoplasmic reticulum membrane, are exposed on the surface of microsomal vesicles, while those of secretory proteins are enclosed inside the vesicles. Therefore, the topographical separation of microsomal membrane proteins from secretory proteins is accomplished at the step of their synthesis by the bound polyribosomes of rough endoplasmic reticulum.

Animals↗

PubMed1977

On the involvement of cytochrome P-450 in the binding of ribosomes to a subfraction of rat-liver rapidly sedimenting endoplasmic reticulum.

Rat liver endoplasmic reticulum has been separated into four ribosome-containing subfractions, two from rapidly sedimentation endoplasmic reticulum and two from the microsomes, by differential centrifugation and sucrose density centrifugation. Ribosomes from one of the rapidly sedimenting subfractions were extracted by Trion X-100 as a complex with cytochrome P-450, optimally at a detergent protein ratio of 2/1 (w/w). Upon extraction approximately 50% of the cytochrome P-450 in the membrane appeared complex-bound to ribosomes, and, maximally, 6-7 subunit molecules of the cytochrome were attached per ribosome. The specific concentration of cytochrome P-450 on these ribosomes was 2.5-times higher than in the parent membrane. Cytochrome b5, glucose-6-phosphatase, NADPH-cytochrome c reductase, NADH-ferricyanide reductase, cytochrome oxidase and phospholipids were present in small or trace amounts on the ribosomes in relation to cytochrome P-450. Ribosomes extracted from other subfractions contained much less bound cytochrome P-450. Phenobarbital treatment induced an increase in the cytochrome P-450 content that was different for the various subfractions. This increase could not be correlated with changes in the amounts of cytochrome-ribosome complexes released by detergent. We propose that cytochrome P-450 is part of a specific binding site in the membrane for a fraction of the ribosomes attached to the endoplasmic reticulum. The ribosomes may be anchored to cytochrome P-450 via nascent chain proteins.

Animals↗

PubMed1976

Energy-dependent calcium transport in endoplasmic reticulum of adipocytes.

The endoplasmic reticulum from isolated rat adipocytes has the ability to actively accumulate calcium. The calcium uptake was characterized using the 20,000 X g supernatant (S1 fraction) of total cellular homogenate. Endoplasmic reticulum vesicles isolated from the S1 fraction as a 160,000 X g microsomal pellet prior to testing demonstrated little ability to accumulate calcium. The calcium uptake in the S1 fraction was localized to the endoplasmic reticulum vesicles by morphologic appearance, by the use of selective inhibitors of calcium uptake, and by high speed sedimentation of the accumulated calcium. The uptake was MgATP- and temperature-dependent and was sustained by the oxalate used as the intravesicular trapping agent. Uptake was linear with time for at least 30 min at all calcium concentrations tested (3 to 100 muM) and exhibited a pH optimum of approximately 7.0. The sulfhydryl inhibitor p-chloromercuribenzene sulfonate produced a dose-dependent inhibition of calcium uptake with total inhibition at 0.07 mumol/mg protein. Ruthenium red and sodium azide inhibited less than 5% of the uptake at concentrations (5 muM and 10 mM, respectively) which completely blocked calcium uptake by mitochondria isolated from the same cells. The Km for calcium uptake was 10 muM total calcium which corresponded to approximately 3.6 muM ionized calcium in the assay system. The maximum velocity of the uptake was 5.0 nmol (mg of microsomal protein)-1 (min)-1 at 24 degrees under the assay conditions used and exhibited a Q10 of 1.8. The uptake activity of the endoplasmic reticulum vesicles in the S1 fraction exhibited a marked time- and temperature-dependent lability which might account in part for the lack of uptake in the isolated microsomal fraction. This energy-dependent calcium uptake system would appear to be of physiologic importance to the regulation of intracellular calcium.

4-Chloromercuribenzenesulfonate↗

PubMed1978

The in vitro reassembly of rough endoplasmic reticulum: ribosome binding capacity.

Rough endoplasmic reticulum membranes were dissolved in 1% deoxycholate and the deoxycholate was then dialysed out for five days. Well-defined bilayer vesicles were formed only if the dialysis was performed at room temperature for the first six hours. The vesicles were separated into a pelleted fraction (Fraction 1) and a fluffy layer (Fraction II) by centrifugation. As measured by amino acid incorporation ability, Fraction II bound polysomes, while Fraction I did not. When smooth endoplasmic reticulum was assembled, it was found that Fraction II so derived had a polysome binding capacity which was more sensitive to increased KCl concentrations (25 mM - 100 mM KCl) and that it bound significantly more monosomes than the corresponding fraction derived from rough membranes. The SDS-polyacrylamide polypeptide patterns of the various fractions were compared.

Binding Sites↗

PubMed1979

The effect of dietary fats on the composition of the liver endoplasmic reticulum and oxidative drug metabolsim.

1. The dependence of the rate of oxidative demethylation in the liver endoplasmic reticulum on the fatty acid composition of the endoplasmic reticulum has been studied by varying the lipid content of the diet. 2. The rate of oxidative demethylation was markedly dependent on the percentage of linoleic acid (18:2) incorporated into the membrane. Feeding diets containing (g/kg) 100 coconut oil, 100 lard or 100 maize oil caused respectively the incorporation of 7.6, 10.3 and 25.1% linoleic acid (18:2) and a demethylation rate 3.26, 3.15 and 5.03 nmol formaldehyde/min per mg protein. Feeding 100 g herring oil/kg diet caused incorporation of only 5.1% C18:2 but also 27.2% omega 3 unsaturated fatty acids, including 8.7% eicosapentaenoic acid (20:5) and 17.0% docosahexaenoic acid (22.6) and caused a very high rate of oxidative demethylation (6.53 nmol formaldehyde/min per mg protein). 3. Destruction of the polyunsaturated fatty acids in herring oil by irradiation with 400 krad caused incorporation of a smaller quantity of 3 omega unsaturated acids into the endoplasmic reticulum and decreased the rate of oxidative demethylation (4.83 nmol formaldehyde/min per mg protein). 4. The inductive effects of phenobarbitone on oxidative demethylation were partially dependent on changes in the fatty acid composition of the endoplasmic reticulum. Phenobarbitone (100 mg/kg) increased the percentage of C18:2 from 25.1 to 29.4% in rats given a maize-oil diet, increased the percentage of C20:5 from 8.7 to 10.3% in rats given a herring-oil diet and decreased the percentage of arachidonic acid (20:4) and C22.6 in rats given a lard, maize-oil, herring-oil or irradiated-herring-oil diet. 5. Intraperitoneal alpha-tocopherol (50 mg/kg) increased the percentage of C20:4 from 11.1 to 13.1% in rats given a lard diet and from 5.9 to 7.3% in rats given a herring-oil diet. 6. It is concluded that dietary C18:2 is an important factor in the regulation of the rate of oxidative demethylation in the liver endoplasmic reticulum but this may be replaced effectively by dietary C20:5 omega 3 and C22:6 omega 3 acids. Oxidative demethylation is regulated by changes in the fatty acid composition of the membranes of the liver endoplasmic reticulum.

Aminopyrine↗

PubMed1976

Direct association of messenger RNA labeled in the presence of fluoroorotate with membranes of the endoplasmic reticulum in rat liver.

Liver rough endoplasmic reticulum (RER) membranes were isolated from rats given [3H]orotic acid for 48 h (ribosomal RNA [rRNA] label) or for 3 h along with 5-fluoroorotate; this latter procedure permits the labeling of cytoplasmic messenger RNAs (mRNAs) in the absence of rRNA labeling. More than 50% of the labeled mRNA remained attached to membranes of the RER after complete removal of ribosomes with a buffer of high ionic strength in the presence of puromycin. Under similar conditions, membranes retained 40% of their polyadenylate as determined by a [3H]-polyuridylate hybridization assay. Treatment of mRNA-labeled endoplasmic reticulum membranes with pancreatic RNase indicates that the polyadenylate and possibly nonpolyadenylate-pyrimidine portions of the messenger are involved in the binding of mRNA to the membranes. The implication of these results in furthering our understanding of the mechanisms of the translational regulation of genetic expression is discussed.

Animals↗

PubMed1979

The smooth endoplasmic reticulum in neurohypophysial axons of the rat: possible involvement in transport, storage and release of neurosecretory material.

The intra-axonal organization of the smooth endoplasmic reticulum was studied in the neurohypophysis of rats during and after water deprivation. Parallel to conventional electron microscopy, the material was treated with a double impregnation staining technique specifically designed to contrast the intracellular membranous system. In conventionally stained ultrathin sections from severely dehydrated rats most axons appeared to be free of membranous organelles, whereas corresponding axons treated with the double-impregnation technique generally exhibited a highly developed system of smooth endoplasmic reticulum. In axonal endings, both techniques revealed a profusion of microvesicles in intimate relationship with tubular elements of the smooth endoplasmic reticulum. In short-term (12h) rehydrated rats, a similarly developed system of smooth endoplasmic reticulum was stilll observed at all axonal levels with both procedures. After 24 to 48 h or rehydration the tubules of the smooth endoplasmic reticulum exhibited, in double impregnated material, numerous dilatations which resembled the adjacent neurosecretory granules. In conventionally stained ultrathin sections, an accumulation of electron dense material occurred within tubules of the smooth endoplasmic reticulum in the more proximal axonal segments, while in the more terminal segments, which contained numerous elongated granules, membrane continuity was frequently observed between newly formed granules and the smooth endoplasmic reticulum. After 7 days of rehydration the general pattern of the axonal smooth endoplasmic reticulum was comparable to that in untreated rats. These results are discussed in the light of a suggested involvement of the axonal smooth endoplasmic reticulum in the non-granlular transport of neurosecretory material in connection with (1) storage in distally formed granules, and (2) release via microvesicles.

Animals↗

PubMed1976

Protein phosphorylation of the smooth and rough endoplasmic reticulum in normal and neoplastic liver of the rat.

Smooth and rough endoplasmic reticulum from rat liver and hepatomas exhibited endogenous protein kinase activity independent of adenosine 3':5'-monophosphate. The phosphorylation of smooth membranes by this process was consistently higher than that of rough membranes. When histone was added along with the smooth endoplasmic reticulum, cyclic AMP stimulated protein phosphorylation. Analysis of membrane-phosphorylated proteins by gel electrophoresis showed 5 major phosphorylated bands with estimated molecular weights of 155 000, 62 000, 50 000, 46 000 and 43 000, whereas major bands having estimated molecular weights of 62 000, 50 000 and 43 000 were found in membranes of the smooth endoplasmic reticulum of the Morris hepatoma 5123 C. Since previous studies in this and other laboratories have demonstrated the similarity of the protein components of membranes of the endoplasmic reticulum of normal liver and hepatoma, our findings indicate an inability of the protein kinase of hepatoma intracellular membranes to phosphorylate protein species that are found in membranes of both liver and the neoplasm.

Animals↗

PubMed1977

Properties of passive binding of calcium to endoplasmic reticulum from adipocytes.

Calcium binding to isolated adipocyte microsomes enriched in endoplasmic reticulum has been characterized. Binding was concentration-dependent, saturable, and totally dissociable. Steady state was reached within 20 min at all calcium concentrations tested. Three apparent classes of binding sites were identified in kinetic and steady state studies using calcium concentrations from 1 muM to 10 mM. The affinity constants (and maximum binding capacities) as determined by computer analysis for the three classes were 2.1 X 10(5) M-1 (0.28 nmol of calcium/mg of protein), 1.3 X 10(4) M-1 (1.1 nmol/mg), and 1.3 X 10(2) M-1 (35 nmol/mg). The dissociation rate constants for the high and intermediate affinity classes of sites were 1.6 X 10(-3) S-1, respectively, and the association rate constant for the high affinity sites was 8 X 10(2) M-1 S-1. The affinity constant calculated from the rate constants was 5.0 X 10(5) M-1 for the high affinity sites in agreement with the value obtained in studies at steady state. The three classes of binding sites were specific for calcium. Magnesium was a noncompetitive inhibitor of calcium binding to all three classes of sites with a Ki of 9 to 12 mM. Calcium binding at 1 muM calcium was 50% inhibited by 18 muM La3+, 600 muM Sr2+, or 2.7 mM Ba2+. These data represent the first analysis of passive calcium binding to endoplasmic reticulum from nonmuscular cells and the first report of corresponding rate constants for either endoplasmic or sarcoplasmic reticulum. The characteristics of the binding are consistent with the properties of calcium transport by endoplasmic reticulum of adipocytes. The characteristics and specificity of the calcium binding constitute further evidence that endoplasmic reticulum plays an important role in cellular calcium homeostasis.

Adipose Tissue↗

PubMed1976

The beads in the Golgi complex-endoplasmic reticulum region.

The region between the rough endoplasmic reticulum (ER) and the Golgi complex has been studied in a variety of insect cell types in an attempt to find a marker for the exit gate or gates from the ER. We have found that the smooth surface of the rough endoplasmic reticulum near Golgi complex transitional elements has beadlike structures arranged in rings at the base of transition vesicles. They occur in all insect cell types and a variety of other organisms. The beads can be seen only after staining in bismuth salts. They are 10-12 nm in diameter and are separated from the membrane and one another by a clear halo giving them a center to center spacing of about 27 nm. The beads are not sensitive to nucleases under conditions which disrupt ribosomes or remove all Feulgen staining material from the nucleus. Under conditions similar to those used to stain tissue, bismuth does not react in vitro with nucleic acids. The component of the beads that stains preferentially with bismuth is therefore probably not nucleic acid.

Bismuth↗

PubMed1978

Studies of the endoplasmic reticulum and plasma membrane-bound ribosomes in erythropoietic cells.

Erythropoietic cells of 5 species, including man, contain endoplasmic reticulum present as individual cisternae or tubules scattered throughout the cytoplasm of all stages except mature RBCs. The endoplasmic reticulum is mainly agranular but occurs frequently as a variant of granular ER which is characterized by an asymmetrical and irregular distribution of ribosomes along one cytoplasmic face. In most cells, the endoplasmic reticulum occurs in close proximity to mitochondria or the plasma membrane , suggesting that the organelle may be involved in functions related to these structures, e.g. haem biosynthesis. Endoplasmic reticulum is more abundant in early than in late erythroid cells. Its exact role in RBC development is unclear. Since endoplasmic reticulum could account for 'plasma membrane-bound ribosomes' reported in lysed reticulocytes, studies were performed which ruled out this possibility and which suggested that such ribosomes were an artifact of the lysing conditions. Hypotonic lysis in less than 20 vol. of magnesium-containing buffers yielded ghosts variably contaminated by ribosomes and other structures. Lysis of reticulocytes in 20-30 vol. of magnesium-free buffer or homogenization of whole cells or crude membrane fractions in hypotonic buffer removed virtually all contaminating ribosomes from the purified membrane fraction.

Animals↗

PubMed1978

The role of lipid components of the diet in the regulation of the fatty acid composition of the rat liver endoplasmic reticulum and lipid peroxidation.

The fatty acid compositions of the lipids and the lipid peroxide concentrations and rates of lipid peroxidation were determined in suspensions of liver endoplasmic reticulum isolated from rats fed on synthetic diets in which the fatty acid composition had been varied but the remaining constituents (protein, carbohydrate, vitamins and minerals) kept constant. Stock diet and synthetic diets containing no fat, 10% corn oil, herring oil, coconut oil or lard were used. The fatty acid composition of the liver endoplasmic reticulum lipid was markedly dependent on the fatty acid composition of the dietary lipid. Feeding a herring-oil diet caused incorporation of 8.7% eicosapentaenoic acid (C(20:5)) and 17% docosahexaenoic acid (C(22:6)), but only 5.1% linoleic acid (C(18:2)) and 6.4% arachidonic acid (C(20:4)), feeding a corn-oil diet caused incorporation of 25.1% C(18:2), 17.8% C(20:4) and 2.5% C(22:6) fatty acids, and feeding a lard diet caused incorporation of 10.3% C(18:2), 13.5% C(20:4) and 4.3% C(22:6) fatty acids into the liver endoplasmic-reticulum lipids. Phenobarbitone injection (100mg/kg) decreased the incorporation of C(20:4) and C(22:6) fatty acids into the liver endoplasmic reticulum of rats fed on a lard, corn-oil or herring-oil diet. Microsomal lipid peroxide concentrations and rates of peroxidation in the presence of ascorbate depended on the nature and quantity of the polyunsaturated fatty acids in the diet. The lipid peroxide content was 1.82+/-0.30nmol of malonaldehyde/mg of protein and the rate of peroxidation was 0.60+/-0.08nmol of malonaldehyde/min per mg of protein after feeding a fat-free diet, and the values were increased to 20.80nmol of malonaldehyde/mg of protein and 3.73nmol of malonaldehyde/min per mg of protein after feeding a 10% herring-oil diet in which polyunsaturated fatty acids formed 24% of the total fatty acids. Addition of alpha-tocopherol to the diets (120mg/kg of diet) caused a very large decrease in the lipid peroxide concentration and rate of lipid peroxidation in the endoplasmic reticulum, but addition of the synthetic anti-oxidant 2,6-di-t-butyl-4-methylphenol to the diet (100mg/kg of diet) was ineffective. Treatment of the animals with phenobarbitone (1mg/ml of drinking water) caused a sharp fall in the rate of lipid peroxidation. It is concluded that the polyunsaturated fatty acid composition of the diet regulates the fatty acid composition of the liver endoplasmic reticulum, and this in turn is an important factor controlling the rate and extent of lipid peroxidation in vitro and possibly in vivo.

Animals↗

PubMed2026

Development and Validation of a Prognostic Signature Based on Transcription Factors Associated with Endoplasmic Reticulum Stress in Pancreatic Adenocarcinoma.

BACKGROUND: Endoplasmic reticulum stress (ER stress) plays a crucial role in influencing the malignant behaviors of various tumors. Targeting the expression or degradation of transcription factors (TFs) offers a promising avenue for cancer treatment. However, a detailed understanding of how ER stress affects TF function and their interactions remains limited. This study aims to develop a prognostic model and identify TFs associated with ER stress in pancreatic ductal adenocarcinoma (PDAC). METHODS: We obtained gene expression profiles and corresponding clinical data from The Cancer Genome Atlas (TCGA). To develop a prognostic signature, we performed several analyses, including unsupervised clustering, enrichment analysis, immune infiltration assessment, as well as univariate, LASSO, and multivariate Cox regression analyses. Four transcription factors-STAT1, IRF6, NRF1, and RXRA-were incorporated into a risk model, which was subsequently validated using the GSE dataset. Additionally, we examined IRF6 through quantitative PCR, western blotting, flow cytometry, and immunohistochemistry in vitro using pancreatic cancer cell lines and a tissue microarray. RESULTS: The high-risk group identified by the model exhibited significant associations with immune cell infiltration and poorer survival outcomes, though there was no significant correlation with tumor purity (p = 0.19). Furthermore, IRF6 downregulation in vitro was found to inhibit pancreatic cancer cell proliferation and promote apoptosis. IRF6 depletion also increased the expression of key molecules involved in ER stress at both the transcriptional and translational levels. Immunohistochemical analysis revealed marked differences in IRF6 expression between tumor and adjacent non-tumor tissues (59.29±29.88 vs. 95.22±40.80, p<0.001). CONCLUSION: This study provides evidence that the constructed risk model can effectively predict prognosis in PDAC patients. Transcription factors related to ER stress, such as IRF6, show promise as both prognostic biomarkers and potential therapeutic targets for PDAC.

Humans↗

PubMed1979

Stereological study of endoplasmic reticulum, Golgi complex and secretory granules in the B-cells of normal and alloxan-treated mice.

Different B-cell organelles (lamellar and vesicular endoplasmic reticulum, Golgi complex, whole secretory granules and secretory granule cores) were studied stereologically in pancreatic islets from control mice and mice killed 10 or 60 min following alloxan injection. Ten min following alloxan a significant decrease was observed in the volume, surface and numerical densities of whole secretory granules and their cores, and a significant increase was found in the volume and surface densities of vesicular endoplasmic reticulum. At the 60 min observation time, a significant decrease was seen in the volume density of lamellar endoplasmic reticulum and Golgi complex, and in the volume, surface and numerical densities of whole secretory granules and their cores, and a significant increase was observed in the volume and surface densities of vesicular endoplasmic reticulum, and in the mean values for volume and surface of whole secretory granules and their cores. The stereological data indicate swelling of endoplasmic reticulum, decreased Golgi area, and decreased number and total volume and surface of secretory granules during the first hour after alloxan administration to mice. The observations may be consistent with inhibited insulin synthesis.

Alloxan↗

PubMed1977

Liver endoplasmic reticulum: target site of halocarbon metabolites.

Initial injury produced by exposure of rats to carbon tetrachloride, halothane, vinyl chloride or trichlorethylene appears to involve the endoplasmic reticulum. First, there is dispersion of the ergastoplasm, then vacuolization and degranulation of the rough endoplasmic reticulum with concomitant retraction of the smooth endoplasmic reticulum into tightly clumped tubular aggregates. In addition, membranes in these tubular aggregates seem to undergo supra-molecular disassembly. Along with this structural disorganization, functional capacity of the organelle diminishes. Activation of these halocarbons to toxic species by functional elements of the endoplasmic reticulum is indicated by the enhancement of their toxicity by pretreatment with chemicals which induce components of the mixed function oxidase system and by the formation of certain metabolites and/or covalently bound products. Insight into the molecular mechanisms of membrane injury brought about by these halocarbon hepatotoxins has been provided by the characterization of chemical changes produced, such as increased lipid diene conjugate content, and the patterns of enzyme deactivation.

Animals↗

PubMed1979

Three-dimensional organization of the endoplasmic reticulum in supraoptic neurons of the rat. A structural functional correlation.

Double impregnation staining of tissue was used to study on thick sections the three-dimensional configuration of the peripheral endoplasmic reticulum in neurosecretory neurons of the supraoptic nucleus in control and water-deprived rats. According to the spatial organization of the endoplasmic reticulum, two types of neurons are described in this report: Type I neurons which predominated in control rats (70%) exhibited characteristically large lamellar structures connected to loosely anastomosed tubules. In type II neurons, which prevailed in water-deprived rats (85%) the endoplasmic reticulum had the appearance of a highly-developed network of interconnected tubules, with no lamellar structures. Double impregnation staining combined with high resolution radioautography after [3H]leucine administration showed that the tubular configuration of the endoplasmic reticulum was the main active site of protein synthesis by contrast with the lamellar components, whose activity seemed poor. In terms of protein synthesis, the three-dimensional configuration of the peripheral endoplasmic reticulum of the supraoptic neurons appeared therefore to be closely connected with their functional state.

Animals↗

PubMed1977

Formation of concentric whorls of rough endoplasmic reticulum in the adrenal gland of the Mongolian gerbil.

All cortical cells appeared alike in fetal gerbils of both sexes though glomerulosa cells were distinguishable at the time of birth. Fenestrated cisternae of rough endoplasmic reticulum were observed in all cortical cells of fetal gerbils, but smooth endoplasmic reticulum predominated. Concentric whorls of rough endoplasmic reticulum first appeared in adrenocortical cells at 42 days of age. The whorls developed within cells having abundant smooth endoplasmic reticulum and which were located in the region between the zona fasciculata and zona reticularis. Cells with whorls possibly serve as reserve cells which transform into actively secreting steroid cells in times of stress.

Adrenal Glands↗