scholarly journals Concurrent changes in Dunaliella salina ultrastructure and membrane phospholipid metabolism after hyperosmotic shock.

1988 ◽  
Vol 107 (2) ◽  
pp. 529-538 ◽  
Author(s):  
K J Einspahr ◽  
M Maeda ◽  
G A Thompson
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Volume ◽  
Surface Area ◽  
Dunaliella Salina ◽  
Membrane Surface ◽  
Fold Increase ◽  
Phospholipid Metabolism ◽  
Hyperosmotic Shock ◽  
Nacl Concentration ◽  
Intracellular Organelles

Hyperosmotic shock, induced by raising the NaCl concentration of Dunaliella salina medium from 1.71 to 3.42 M, elicited a rapid decrease of nearly one-third in whole cell volume and in the volume of intracellular organelles. The decrease in cell volume was accompanied by plasmalemma infolding without overall loss of surface area. This contrasts with the dramatic increase in plasmalemma surface area after hypoosmotic shock (Maeda, M., and G. A. Thompson. 1986. J. Cell Biol. 102:289-297). Although plasmalemma surface area remained constant after hyperosmotic shock, the nucleus, chloroplast, and mitochondria lost membrane surface area, apparently through membrane fusion with the endoplasmic reticulum. Thus the endoplasmic reticulum serves as a reservoir for excess membrane during hyperosmotic stress, reversing its role as membrane donor to the same organelles during hypoosmotically induced cell expansion. Hyperosmotic shock also induced rapid changes in phospholipid metabolism. The mass of phosphatidic acid dropped to 56% of control and that of phosphatidylinositol 4,5-bisphosphate rose to 130% of control within 4 min. Further analysis demonstrated that within 10 min after hyperosmotic shock, there was 2.5-fold increase in phosphatidylcholine turnover, a twofold increase in lysophosphatidylcholine mass, a four-fold increase in lysophosphatidate mass, and an elevation in free fatty acids to 124% of control, all observations suggesting activation of phospholipase A. The observed biophysical and biochemical phenomena are likely to be causally interrelated in providing mechanisms for successful accommodation to such severe osmotic extremes.

scholarly journals Integrated stereological and biochemical studies on hepatocytic membranes. I.V. Heterogeneous distribution of marker enzymes on endoplasmic reticulum membranes in fractions.

1980 ◽  
Vol 85 (3) ◽  
pp. 577-586 ◽  
Author(s):  
R P Bolender ◽  
D Paumgartner ◽  
D Muellener ◽  
G Losa ◽  
E R Weibel
Keyword(s):  
Endoplasmic Reticulum ◽  
Surface Area ◽  
Enzyme Activities ◽  
Membrane Surface ◽  
Marker Enzyme ◽  
Marker Enzymes ◽  
Heterogeneous Distribution ◽  
Membrane Surface Area ◽  
Total Membrane ◽  
Nadph Cytochrome C Reductase

The purpose of the study was to consider quantitatively the relationships between the surface area of the endoplasmic reticulum (ER) and constituent marker enzyme activities, as they occur in fractions collected from rat liver homogenates. The ER surface area was estimated in five membrane-containing fractions by use of a combined cytochemical-stereological technique (5), while, at the same time, ER marker enzymes were assayed biochemically. Fraction/homogenate recoveries for the ER enzymes averaged 100%, total membrane surface area 98%, and ER surface area 96%. Relative specific activities, which compare the relative amounts of ER marker enzyme activities to the relative ER surface area in the membrane-containing fractions, indicate variable distributions for glucose-6-phosphatase and NADPH cytochrome c reductase, but not for esterase.

scholarly journals Three-dimensional ATUM-SEM reconstruction and analysis of hepatic endoplasmic reticulum-organelle interactions

2020 ◽  
Author(s):  
Yi Jiang ◽  
Linlin Li ◽  
Xi Chen ◽  
Jiazheng Liu ◽  
Jingbin Yuan ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
3D Reconstruction ◽  
Surface Area ◽  
Lipid Droplets ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Surface Area Ratio ◽  
Intracellular Space ◽  
Membrane Surface Area ◽  
Membrane Contact Sites

AbstractThe endoplasmic reticulum (ER) is a contiguous and complicated membrane network in eukaryotic cells, and membrane contact sites (MCSs) between the ER and other organelles perform vital cellular functions, including lipid homeostasis, metabolite exchange, calcium level regulation, and organelle division. Here, we establish a whole pipeline to reconstruct all ER, mitochondria, lipid droplets, lysosomes, peroxisomes, and nuclei by automated tape-collecting ultramicrotome scanning electron microscopy (ATUM-SEM) and deep-learning techniques, which generates an unprecedented 3D model for mapping liver samples. Furthermore, the morphology of various organelles is systematically analyzed. We found that the ER presents with predominantly flat cisternae and is knitted tightly all throughout the intracellular space and around other organelles. In addition, the ER has a smaller volume-to-membrane surface area ratio than other organelles, which suggests that the ER could be more suited for functions that require a large membrane surface area. Moreover, the MCSs between the ER and other organelles are explored. Our data indicate that ER-mitochondrial contacts are particularly abundant, especially for branched mitochondria. In addition, ER contacts with lipid droplets, lysosomes, and peroxisomes are also plentiful. In summary, we design an efficient method for obtaining a 3D reconstruction of biological structures at a nanometer resolution. Our study also provides the first 3D reconstruction of various organelles in liver samples together with important information fundamental for biochemical and functional studies in the liver.

scholarly journals On the mechanism of rapid plasma membrane and chloroplast envelope expansion in Dunaliella salina exposed to hypoosmotic shock.

1986 ◽  
Vol 102 (1) ◽  
pp. 289-297 ◽  
Author(s):  
M Maeda ◽  
G A Thompson
Keyword(s):  
Plasma Membrane ◽  
Surface Area ◽  
Thin Section ◽  
Dunaliella Salina ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Chloroplast Envelope ◽  
Outer Envelope ◽  
High Concentration ◽  
Selective Fusion

Dunaliella salina cells rapidly diluted from their normal 1.71 M NaCl-containing growth medium into medium containing 0.86 M NaCl swelled within 2--4 min to an average volume 1.76 X larger and a surface area 1.53 X larger than found in control cells. Morphometric analysis of thin section electron micrographs revealed that certain organelles, including the chloroplast, nucleus, and some types of vacuoles, also expanded in surface area as much or more than did the entire cell. It is likely that glycerol, the most important osmotically active intracellular solute, was present in high concentration within these organelles as well as in the cytoplasm itself. Thin section and freeze-fracture electron microscopy were utilized to trace the origin of membrane material whose addition permitted the large increase in plasma membrane surface area and the equally large growth of the chloroplast outer envelope. The findings indicated that the plasma membrane's expansion resulted from its selective fusion with numerous small (less than or equal to 0.25 micron diam) vesicles prevalent throughout the cytoplasm. In contrast, new membrane added to the chloroplast outer envelope was drawn from an entirely different source, namely, elements of the endoplasmic reticulum.

scholarly journals Alterations in cellular and organellar phospholipid compositions of HepG2 cells during cell growth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tokuji Tsuji ◽  
Shin-ya Morita ◽  
Yoshinobu Nakamura ◽  
Yoshito Ikeda ◽  
Taiho Kambe ◽  
...  
Keyword(s):  
Cell Growth ◽  
Hepg2 Cells ◽  
Phospholipid Class ◽  
Present Report ◽  
Phospholipid Metabolism ◽  
Cancer Cell Growth ◽  
Microsomal Membranes ◽  
Intracellular Organelles ◽  
The Relationship ◽  
Pe Ratio

AbstractThe human hepatoblastoma cell line, HepG2, has been used for investigating a wide variety of physiological and pathophysiological processes. However, less information is available about the phospholipid metabolism in HepG2 cells. In the present report, to clarify the relationship between cell growth and phospholipid metabolism in HepG2 cells, we examined the phospholipid class compositions of the cells and their intracellular organelles by using enzymatic fluorometric methods. In HepG2 cells, the ratios of all phospholipid classes, but not the ratio of cholesterol, markedly changed with cell growth. Of note, depending on cell growth, the phosphatidic acid (PA) ratio increased and phosphatidylcholine (PC) ratio decreased in the nuclear membranes, the sphingomyelin (SM) ratio increased in the microsomal membranes, and the phosphatidylethanolamine (PE) ratio increased and the phosphatidylserine (PS) ratio decreased in the mitochondrial membranes. Moreover, the mRNA expression levels of enzymes related to PC, PE, PS, PA, SM and cardiolipin syntheses changed during cell growth. We suggest that the phospholipid class compositions of organellar membranes are tightly regulated by cell growth. These findings provide a basis for future investigations of cancer cell growth and lipid metabolism.

The macrophage capacity for phagocytosis

1992 ◽  
Vol 101 (4) ◽  
pp. 907-913 ◽  
Author(s):  
G.J. Cannon ◽  
J.A. Swanson
Keyword(s):  
Surface Area ◽  
Membrane Surface ◽  
Fc Receptors ◽  
Phagocytic Capacity ◽  
Membrane Surface Area ◽  
Murine Bone Marrow ◽  
Latex Beads ◽  
Endocytic Compartments ◽  
Frustrated Phagocytosis

Murine bone marrow-derived macrophages, which measure 13.8 +/− 2.3 microns diameter in suspension, can ingest IgG-opsonized latex beads greater than 20 microns diameter. A precise assay has allowed the determination of the phagocytic capacity, and of physiological parameters that limit that capacity. Ingestion of beads larger than 15 microns diameter required IgG-opsonization, and took 30 minutes to reach completion. Despite the dependence on Fc-receptors for phagocytosis of larger beads, cells reached their limit before all cell surface Fc-receptors were occupied. The maximal membrane surface area after frustrated phagocytosis of opsonized coverslips was similar to the membrane surface area required to engulf particles at the limiting diameter, indicating that the capacity was independent of particle shape. Vacuolation of the lysosomal compartment with sucrose, which expanded endocytic compartments, lowered the phagocytic capacity. This decrease was reversed when sucrose vacuoles were collapsed by incubation of cells with invertase. These experiments indicate that the phagocytic capacity is limited by the amount of available membrane, rather than by the availability of Fc-receptors. The capacity was also reduced by depolymerization of cytoplasmic microtubules with nocodazole. Nocodazole did not affect the area of maximal cell spreading during frustrated phagocytosis, but did alter the shape of the spread cells. Thus, microtubules may coordinate cytoplasm for engulfment of the largest particles.

scholarly journals Disorders of the erythrocyte membrane

2015 ◽  
Vol 9 (4) ◽  
pp. 323
Author(s):  
Sophia Delicou ◽  
Aikaterini Xydaki ◽  
Chryssanthi Kontaxi ◽  
Konstantinos Maragkos
Keyword(s):  
Surface Area ◽  
Erythrocyte Membrane ◽  
Structural Integrity ◽  
Mechanical Stability ◽  
Hereditary Spherocytosis ◽  
Membrane Surface ◽  
Membrane Skeleton ◽  
Inherited Disorders ◽  
Hereditary Elliptocytosis ◽  
Area Loss

Hemolytic anemia due to abnormalities of the erythrocyte membrane comprises an important group of inherited disorders. These include hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis, and the hereditary stomatocytosis syndromes. The erythrocyte membrane skeleton composed of spectrin, actin, and several other proteins is essential for the maintenance of the erythrocyte shape, reversible deformability, and membrane structural integrity in addition to controlling the lateral mobility of integral membrane proteins. These disorders are characterized by clinical and laboratory heterogeneity and, as evidenced by recent molecular studies, by genetic heterogeneity. Defects in various proteins involved in linking the lipid bilayer to membrane skeleton result in loss in membrane cohesion leading to surface area loss and hereditary spherocytosis while defects in proteins involved in lateral interactions of the spectrin-based skeleton lead to decreased mechanical stability, membrane fragmentation and hereditary elliptocytosis. The disease severity is primarily dependent on the extent of membrane surface area loss. Treatment with splenectomy is curative in most patients.

scholarly journals Intracellular Ca2+ Release and Synaptic Plasticity: A Tale of Many Stores

2018 ◽  
Vol 25 (3) ◽  
pp. 208-226 ◽  
Author(s):  
Zahid Padamsey ◽  
William J. Foster ◽  
Nigel J. Emptage
Keyword(s):  
Endoplasmic Reticulum ◽  
Synaptic Plasticity ◽  
Synaptic Function ◽  
Intracellular Organelles ◽  
Short And Long Term ◽  
Central Synapses ◽  
Neural Signaling ◽  
Temporal Extent

Ca2+ is an essential trigger for most forms of synaptic plasticity. Ca2+ signaling occurs not only by Ca2+ entry via plasma membrane channels but also via Ca2+ signals generated by intracellular organelles. These organelles, by dynamically regulating the spatial and temporal extent of Ca2+ elevations within neurons, play a pivotal role in determining the downstream consequences of neural signaling on synaptic function. Here, we review the role of three major intracellular stores: the endoplasmic reticulum, mitochondria, and acidic Ca2+ stores, such as lysosomes, in neuronal Ca2+ signaling and plasticity. We provide a comprehensive account of how Ca2+ release from these stores regulates short- and long-term plasticity at the pre- and postsynaptic terminals of central synapses.

scholarly journals Effect Of Surface Area Of Dialyzer Membrane On The Adequacy Of Haemodialysis

2012 ◽  
Vol 7 (2) ◽  
pp. 9-11 ◽  
Author(s):  
NS Chowdhury ◽  
FMM Islam ◽  
F Zafreen ◽  
BA Begum ◽  
N Sultana ◽  
...  
Keyword(s):  
Renal Disease ◽  
Surface Area ◽  
End Stage Renal Disease ◽  
Membrane Surface ◽  
Reduction Ratio ◽  
Urea Clearance ◽  
Membrane Surface Area ◽  
Stage Renal Disease ◽  
End Stage ◽  
Urea Reduction Ratio

Introduction: Patients with end stage renal disease require 12 hours of haemodialysis per week in three equal sessions (4 hours/day for 3 days/week). But the duration and frequency of treatment can be reduced by increasing the surface area of the dialyzer membrane. Methods: In this prospective study 40 patients of end stage renal disease receiving haemodialysis for more than six months were included to observe the effects of increment in the surface area of the dialyzer membrane on the adequacy of haemodialysis. Result: It was observed that 20 patients receiving haemodialysis on a dialyzer with membrane surface area of 1.2 m² did not have satisfactory solute clearance index. Urea reduction ratio was 45.9 ± 3.03 and fractional urea clearance (Kt/V) was 0.76 ± 0.09. On the other hand patients (20 cases) receiving haemodialysis on a dialyzer with membrane surface area of 1.3 m² had a urea reduction ratio 50.76± 5.16 and fractional urea clearance (Kt/V) 0.91 ± 0.16. All the patients of both groups received dialysis for 8 hours/week in two equal sessions (4 hours/day for 2 days/week). Statistically the increment was significant (p<0.001). Conclusion: This study reveals, adequacy of dialysis can be increased by increasing the surface area of the dialyzer membrane. So, considering the poor socioeconomic condition of Bangladesh and patients' convenience, a short duration, low cost dialysis regime can be tried by increasing the surface area of dialyzer membrane. DOI: http://dx.doi.org/10.3329/jafmc.v7i2.10387 JAFMC 2011; 7(2): 9-11

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