Control of cell shape by calcium in the euglenophyceae

1981 ◽  
Vol 49 (1) ◽  
pp. 99-117 ◽  
Author(s):  
J.M. Murray
Keyword(s):  
Endoplasmic Reticulum ◽  
Atpase Activity ◽  
Calcium Oxalate ◽  
Cell Shape ◽  
Motor Units ◽  
Astasia Longa ◽  
Oxalate Precipitation ◽  
Entire Cell ◽  
The Individual ◽  
Euglenoid Movement

The euglenoid flagellates are able to change their shape rapidly in response to a variety of stimuli, or sometimes spontaneously. Two extremes of shape can be identified: the “relaxed” form is cylindrical; the contracted form is a somewhat distorted disc. These 2 forms can be interconverted by treatments that alter the Ca2+ concentration of the entire cell. The level of Ca2+ is believed to be normally controlled by a system of calcium-accumulating membranes, identified in Astasia longa by the technique of calcium oxalate precipitation. The system forms a set of parallel tubes of endoplasmic reticulum, one of which lies immediately below each of the ridges of the pellicle. The individual ridges, each with its associated reticulum, microtubules and other elements are suggested to be independent motor units. Local activation of a small number of these units by Ca2+ is made possible by the arrangement of Ca2+ -sequestering reticulum, producing the characteristic squirming euglenoid movement. Uniform activation or suppression of all units produces the 2 extremes of shape. The pellicle of A. longa with its associated microtubules has been purified and shown to contain a Ca2+ -binding site and ATPase activity.

scholarly journals Hepatic endosome fractions contain an ATP-driven proton pump

1985 ◽  
Vol 225 (1) ◽  
pp. 51-58 ◽  
Author(s):  
T Saermark ◽  
N Flint ◽  
W H Evans
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Atpase Activity ◽  
Proton Pump ◽  
Subcellular Distribution ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Ph Gradients ◽  
Subcellular Organelle ◽  
Liver Homogenates

Endosome fractions were isolated from rat liver homogenates on the basis of the subcellular distribution of circulating ligands, e.g. 125I-asialotransferrin internalized by hepatocytes by a receptor-mediated process. The distribution of endocytosed 125I-asialotransferrin 1-2 min and 15 min after uptake by liver and a monensin-activated Mg2+-dependent ATPase activity coincided on linear gradients of sucrose and Nycodenz. The monensin-activated Mg2+-ATPase was enriched relative to the liver homogenates up to 60-fold in specific activity in the endosome fractions. Contamination of the endosome fractions by lysosomes, endoplasmic reticulum, mitochondria, plasma membranes and Golgi-apparatus components was low. By use of 9-aminoacridine, a probe for pH gradients, the endosome vesicles were shown to acidify on addition of ATP. Acidification was reversed by addition of monensin. The results indicate that endosome fractions contain an ATP-driven proton pump. The ionophore-activated Mg2+-ATPase in combination with the presence of undegraded ligands in the endosome fractions emerge as linked markers for this new subcellular organelle.

Nephrolithiasis

2018 ◽  
Author(s):  
José Luiz Nishiura ◽  
Ita Pfeferman Heilberg
Keyword(s):  
Uric Acid ◽  
Calcium Oxalate ◽  
Dietary Habits ◽  
Stone Formation ◽  
Urine Volume ◽  
First Episode ◽  
Dietary Advice ◽  
Dietary Recommendations ◽  
Genetic Traits ◽  
Oxalate Precipitation

Nephrolithiasis is a highly prevalent condition, but its incidence varies depending on race, gender, and geographic location. Approximately half of patients form at least one recurrent stone within 10 years of the first episode. Renal stones are usually composed of calcium salts (calcium oxalate monohydrate or dihydrate, calcium phosphate), uric acid, or, less frequently, cystine and struvite (magnesium, ammonium, and phosphate). Calcium oxalate stones, the most commonly encountered ones, may result from urinary calcium oxalate precipitation on the Randall plaque, which is a hydroxyapatite deposit in the interstitium of the kidney medulla. Uric acid nephrolithiasis, which is common among patients with metabolic syndrome or diabetes mellitus, is caused by an excessively acidic urinary pH as a renal manifestation of insulin resistance. The medical evaluation of the kidney stone patient must be focused on identifying anatomic abnormalities of the urinary tract, associated systemic diseases, use of lithogenic drugs or supplements, and, mostly, urinary risk factors such as low urine volume, hypercalciuria, hyperuricosuria, hypocitraturia, hyperoxaluria, and abnormalities in urine pH that can be affected by dietary habits, environmental factors, and genetic traits. Metabolic evaluation requires a urinalysis, stone analysis (if available), serum chemistry, and urinary parameters, preferably obtained by two nonconsecutive 24-hour urine collections under a random diet. Targeted medication and dietary advice are effective to reduce the risk of recurrence. Clinical, radiologic, and laboratory follow-ups are needed to prevent stone growth and new stone formation, to assess treatment adherence or effectiveness to dietary recommendations, and to allow adjustment of pharmacologic treatment. This review contains 5 highly rendered figure, 3 tables, and 105 references.

Autonomy and non-autonomy in Drosophila mesoderm determination and morphogenesis

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 853-859 ◽  
Author(s):  
M. Leptin ◽  
S. Roth
Keyword(s):  
Cell Shape ◽  
Shape Change ◽  
Developmental Program ◽  
Cell Shape Change ◽  
Ventral Furrow ◽  
Large Numbers ◽  
The Individual ◽  
Mutant Cells ◽  
Transplantation Experiments ◽  
Shape Changes

The mesoderm in Drosophila invaginates by a series of characteristic cell shape changes. Mosaics of wild-type cells in an environment of mutant cells incapable of making mesodermal invaginations show that this morphogenetic behaviour does not require interactions between large numbers of cells but that small patches of cells can invaginate independent of their neighbours' behaviour. While the initiation of cell shape change is locally autonomous, the shapes the cells assume are partly determined by the individual cell's environment. Cytoplasmic transplantation experiments show that areas of cells expressing mesodermal genes ectopically at any position in the egg form an invagination. We propose that ventral furrow formation is the consequence of all prospective mesodermal cells independently following their developmental program. Gene expression at the border of the mesoderm is induced by the apposition of mesodermal and non-mesodermal cells.

Nephrolithiasis

2017 ◽  
Author(s):  
José Luiz Nishiura ◽  
Ita Pfeferman Heilberg
Keyword(s):  
Uric Acid ◽  
Calcium Oxalate ◽  
Dietary Habits ◽  
Stone Formation ◽  
Urine Volume ◽  
First Episode ◽  
Dietary Advice ◽  
Dietary Recommendations ◽  
Genetic Traits ◽  
Oxalate Precipitation

Nephrolithiasis is a highly prevalent condition, but its incidence varies depending on race, gender, and geographic location. Approximately half of patients form at least one recurrent stone within 10 years of the first episode. Renal stones are usually composed of calcium salts (calcium oxalate monohydrate or dihydrate, calcium phosphate), uric acid, or, less frequently, cystine and struvite (magnesium, ammonium, and phosphate). Calcium oxalate stones, the most commonly encountered ones, may result from urinary calcium oxalate precipitation on the Randall plaque, which is a hydroxyapatite deposit in the interstitium of the kidney medulla. Uric acid nephrolithiasis, which is common among patients with metabolic syndrome or diabetes mellitus, is caused by an excessively acidic urinary pH as a renal manifestation of insulin resistance. The medical evaluation of the kidney stone patient must be focused on identifying anatomic abnormalities of the urinary tract, associated systemic diseases, use of lithogenic drugs or supplements, and, mostly, urinary risk factors such as low urine volume, hypercalciuria, hyperuricosuria, hypocitraturia, hyperoxaluria, and abnormalities in urine pH that can be affected by dietary habits, environmental factors, and genetic traits. Metabolic evaluation requires a urinalysis, stone analysis (if available), serum chemistry, and urinary parameters, preferably obtained by two nonconsecutive 24-hour urine collections under a random diet. Targeted medication and dietary advice are effective to reduce the risk of recurrence. Clinical, radiologic, and laboratory follow-ups are needed to prevent stone growth and new stone formation, to assess treatment adherence or effectiveness to dietary recommendations, and to allow adjustment of pharmacologic treatment. This review contains 5 highly rendered figure, 3 tables, and 105 references.

Heterologous expression of Na+-K+-ATPase in insect cells: intracellular distribution of pump subunits

2001 ◽  
Vol 281 (3) ◽  
pp. C982-C992 ◽  
Author(s):  
Craig Gatto ◽  
Scott M. McLoud ◽  
Jack H. Kaplan
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Protein ◽  
Atpase Activity ◽  
Insect Cells ◽  
Expression System ◽  
Β Subunit ◽  
Α Subunit ◽  
Enzyme Preparations ◽  
High Five Cells

The Na+-K+-ATPase is a heterodimeric plasma membrane protein responsible for cellular ionic homeostasis in nearly all animal cells. It has been shown that some insect cells (e.g., High Five cells) have no (or extremely low) Na+-K+-ATPase activity. We expressed sheep kidney Na+-K+-ATPase α- and β-subunits individually and together in High Five cells via the baculovirus expression system. We used quantitative slot-blot analyses to determine that the expressed Na+-K+-ATPase comprises between 0.5% and 2% of the total membrane protein in these cells. Using a five-step sucrose gradient (0.8–2.0 M) to separate the endoplasmic reticulum, Golgi apparatus, and plasma membrane fractions, we observed functional Na+ pump molecules in each membrane pool and characterized their properties. Nearly all of the expressed protein functions normally, similar to that found in purified dog kidney enzyme preparations. Consequently, the measurements described here were not complicated by an abundance of nonfunctional heterologously expressed enzyme. Specifically, ouabain-sensitive ATPase activity, [3H]ouabain binding, and cation dependencies were measured for each fraction. The functional properties of the Na+-K+-ATPase were essentially unaltered after assembly in the endoplasmic reticulum. In addition, we measured ouabain-sensitive 86Rb+ uptake in whole cells as a means to specifically evaluate Na+-K+-ATPase molecules that were properly folded and delivered to the plasma membrane. We could not measure any ouabain-sensitive activities when either the α-subunit or β-subunit were expressed individually. Immunostaining of the separate membrane fractions indicates that the α-subunit, when expressed alone, is degraded early in the protein maturation pathway (i.e., the endoplasmic reticulum) but that the β-subunit is processed normally and delivered to the plasma membrane. Thus it appears that only the α-subunit has an oligomeric requirement for maturation and trafficking to the plasma membrane. Furthermore, assembly of the α-β heterodimer within the endoplasmic reticulum apparently does not require a Na+pump-specific chaperone.

scholarly journals TSH/cAMP up-regulate sarco/endoplasmic reticulum Ca2+-ATPases expression and activity in PC Cl3 thyroid cells

2004 ◽  
pp. 851-861 ◽  
Author(s):  
L Ulianich ◽  
A Secondo ◽  
S De Micheli ◽  
S Treglia ◽  
F Pacifico ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Atpase Activity ◽  
Specific Inhibitor ◽  
Intracellular Camp ◽  
Western Blots ◽  
Thyroid Cells ◽  
Dependent Protein ◽  
Main Regulator ◽  
Rat Thyroid ◽  
Expression And Activity

OBJECTIVE: We recently reported that the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) 2b is the SERCA form preferentially expressed in rat thyroid. Moreover, SERCA2b expression dramatically decreases in virally transformed, highly tumorigenic, PC Cl3 thyroid cells. These results suggest that, in the thyroid, SERCA2b, in addition to its housekeeping role, is linked to differentiation and is a regulated gene. We therefore sought to study the effect of TSH, the main regulator of thyroid function, on SERCA2b expression and activity. METHODS: PC Cl3 cells were hormone starved in low-serum medium and stimulated for long (48 h) or short (1, 2 and 4 h) times. SERCA2b expression and activity were evaluated by Northern and Western blots, Ca2+-ATPase activity and Ca2+ store content. RESULTS: In PC Cl3 cells, SERCA2b mRNA and protein were induced twofold by a 48-h long treatment with TSH. Long-term elevation (48 h) of intracellular cAMP levels, by forskolin or 8-Br-cAMP, had similar effects on SERCA2b mRNA and protein. We also measured Ca2+-ATPase activity and Ca2+ store content. Both long (48 h) and short (0.5-1 h) treatments with TSH, forskolin or 8-Br-cAMP induced a marked increase of SERCA2b activity. This effect was completely abolished by H89, a specific inhibitor of cAMP-dependent protein kinase A (PKA). TSH and 8-Br-cAMP increased Ca2+ store content after both long (48 h) and short (1-2 h) treatments. CONCLUSIONS: These data suggested that TSH/cAMP acts as an important regulator of both SERCA2b expression and activity in the thyroid system, through PKA activation.

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