Dietary fats and properties of endoplasmic reticulum: I. Dietary lipid induced changes in composition of microsomal membranes in liver and gastroduodenal mucosa of rat

Lipids ◽  
1975 ◽  
Vol 10 (8) ◽  
pp. 461-466 ◽  
Author(s):  
M. Laitinen ◽  
E. Hietanen ◽  
H. Vainio ◽  
O. Hänninen
Keyword(s):  
Endoplasmic Reticulum ◽  
Dietary Lipid ◽  
Dietary Fats ◽  
Gastroduodenal Mucosa ◽  
Microsomal Membranes ◽  
Induced Changes

scholarly journals Environmentally induced changes in mitochondria and endoplasmic reticulum of Saccharomyces carlsbergensis yeast.

1976 ◽  
Vol 71 (1) ◽  
pp. 123-135 ◽  
Author(s):  
C H Damsky
Keyword(s):  
Endoplasmic Reticulum ◽  
Surface Density ◽  
Volume Density ◽  
Sharp Reduction ◽  
Inner Mitochondrial Membrane ◽  
Large Fluctuations ◽  
Mitochondrial Volume ◽  
Culture Environment ◽  
Induced Changes

The effects of culture environment on the volume density and surface density of mitochondria and endoplasmic reticulum in a facultative yeast were studied. When compared with cells grown aerobically on a nonrepressive substrate, cells grown in the absence of oxygen showed a sharp reduction in both volume density of mitochondria and surface density of the inner mitochondrial membrane (imm) in the remaining mitochondrial profiles. Use of fermentable (repressive) substrates under aerobic conditions restricted the volume density of mitochondria to a much greater extent than the surface density of imm. The range of mitochondrial volume densities in these experiments was 4-11%. Surface density of endoplasmic reticulum (ER) was sensitive to growth rate and in particular to changes in oxygen tension, showing large fluctuations during both anaerobic and aerobic adaptation. These fluctuations in ER are discussed in relation to the known role of this organelle in lipid metabolism.

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.

scholarly journals Subcellular distribution and characteristics of trihydroxycoprostanoyl-CoA synthetase in rat liver

1989 ◽  
Vol 257 (1) ◽  
pp. 221-229 ◽  
Author(s):  
L Schepers ◽  
M Casteels ◽  
K Verheyden ◽  
G Parmentier ◽  
S Asselberghs ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cholic Acid ◽  
Rat Liver ◽  
Subcellular Distribution ◽  
The Other ◽  
Acid Activation ◽  
Long Chain Fatty Acids ◽  
Microsomal Membranes ◽  
Triton X ◽  
Long Chain

The subcellular distribution and characteristics of trihydroxycoprostanoyl-CoA synthetase were studied in rat liver and were compared with those of palmitoyl-CoA synthetase and choloyl-CoA synthetase. Trihydroxycoprostanoyl-CoA synthetase and choloyl-CoA synthetase were localized almost completely in the endoplasmic reticulum. A quantitatively insignificant part of trihydroxycoprostanoyl-CoA synthetase was perhaps present in mitochondria. Peroxisomes, which convert trihydroxycoprostanoyl-CoA into choloyl-CoA, were devoid of trihydroxycoprostanoyl-CoA synthetase. As already known, palmitoyl-CoA synthetase was distributed among mitochondria, peroxisomes and endoplasmic reticulum. Substrate- and cofactor- (ATP, CoASH) dependence of the three synthesis activities were also studied. Cholic acid and trihydroxycoprostanic acid did not inhibit palmitoyl-CoA synthetase; palmitate inhibited the other synthetases non-competitively. Likewise, cholic acid inhibited trihydroxycoprostanic acid activation non-competitively and vice versa. The pH curves of the synthetases did not coincide. Triton X-100 affected the activity of each of the synthetases differently. Trihydroxycoprostanoyl-CoA synthetase was less sensitive towards inhibition by pyrophosphate than choloyl-CoA synthetase. The synthetases could not be solubilized from microsomal membranes by treatment with 1 M-NaCl, but could be solubilized with Triton X-100 or Triton X-100 plus NaCl. The detergent-solubilized trihydroxycoprostanoyl-CoA synthetase could be separated from the solubilized choloyl-CoA synthetase and palmitoyl-CoA synthetase by affinity chromatograpy on Sepharose to which trihydroxycoprostanic acid was bound. Choloyl-CoA synthetase and trihydroxycoprostanoyl-CoA synthetase could not be detected in homogenates from kidney or intestinal mucosa. The results indicate that long-chain fatty acids, cholic acid and trihydroxycoprostanic acid are activated by three separate enzymes.

scholarly journals Target of rapamycin signaling mediates vacuolar fission caused by endoplasmic reticulum stress in Saccharomyces cerevisiae

2015 ◽  
Vol 26 (25) ◽  
pp. 4618-4630 ◽  
Author(s):  
Bobbiejane Stauffer ◽  
Ted Powers
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Intracellular Localization ◽  
Downstream Effectors ◽  
Genome Wide ◽  
Genetic Perturbations ◽  
Response To Stress ◽  
Induced Changes ◽  
Yeast Mutants

The yeast vacuole is equivalent to the mammalian lysosome and, in response to diverse physiological and environmental stimuli, undergoes alterations both in size and number. Here we demonstrate that vacuoles fragment in response to stress within the endoplasmic reticulum (ER) caused by chemical or genetic perturbations. We establish that this response does not involve known signaling pathways linked previously to ER stress but instead requires the rapamycin-sensitive TOR Complex 1 (TORC1), a master regulator of cell growth, together with its downstream effectors, Tap42/Sit4 and Sch9. To identify additional factors required for ER stress–induced vacuolar fragmentation, we conducted a high-throughput, genome-wide visual screen for yeast mutants that are refractory to ER stress–induced changes in vacuolar morphology. We identified several genes shown previously to be required for vacuolar fusion and/or fission, validating the utility of this approach. We also identified a number of new components important for fragmentation, including a set of proteins involved in assembly of the V-ATPase. Remarkably, we find that one of these, Vph2, undergoes a change in intracellular localization in response to ER stress and, moreover, in a manner that requires TORC1 activity. Together these results reveal a new role for TORC1 in the regulation of vacuolar behavior.

scholarly journals Immunoelectron microscope localization of cytochrome P-450 on microsomes and other membrane structures of rat hepatocytes.

1978 ◽  
Vol 78 (2) ◽  
pp. 503-519 ◽  
Author(s):  
S Matsuura ◽  
Y Fujii-Kuriyama ◽  
Y Tashiro
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membranes ◽  
Control Level ◽  
Rat Hepatocytes ◽  
Present Observation ◽  
Membrane Structures ◽  
Rat Liver Cells ◽  
Microsomal Membranes ◽  
Almost All ◽  
Cytochrome P 450

Localization of cytochrome P-450 on various membrane fractions of rat liver cells was studied by direct immunoelectron microscopy using ferritin-conjugated antibody to the cytochrome. The outer surfaces of almost all the microsomal vesicles were labeled with ferritin particles. The distribution of the particles on each microsomal vesicle was usually heterogeneous, indicating clustering of the cytochrome, and phenobarbital treatment markedly increased the labeled regions of the microsomal membranes. The outer nuclear envelopes were also labeled with ferritin particles, while on the surface of other membrane structures such as Golgi complexes, outer mitochondrial membranes and plasma membranes the labeling was scanty and at the control level. The present observation indicates that cytochrome P-450 molecules are localized exclusively on endoplasmic reticulum membranes and outer nuclear envelopes where they are probably distributed not uniformly but heterogeneously, forming clusters or patches. The physiological significance of such microheterogeneity in the distribution of the cytochrome on endoplasmic reticulum membranes is discussed.

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