scholarly journals Phosphate Uptake by Phosphate-Starved Euglena

1966 ◽  
Vol 49 (6) ◽  
pp. 1125-1137 ◽  
Author(s):  
J. J. BLUM
Keyword(s):  
Acid Phosphatase ◽  
Low Temperature ◽  
Active Transport ◽  
Transport Process ◽  
Phosphate Uptake ◽  
Uptake System ◽  
Low Concentrations ◽  
Na Ions ◽  
Active Transport Process ◽  
Rule Out

Phosphate-deprived Euglena acquire the ability to rapidly in-corporate added phosphate and, also, synthesize an induced acid phosphatase localized in the pellicle. The phosphate uptake system is saturated at low concentrations of phosphate and is inhibited by dinitrophenol, by low temperature, by K+, Li+, and Na+ ions, and competitively by arsenate. The orthophosphate incorporated into the cell is rapidly converted into organic forms but enough remains unesterified to suggest that the uptake is an active transport process. The data do not rule out the possibility that the induced phosphatase is involved in the transport process.

A nuclear localization signal can enhance both the nuclear transport and expression of 1 kb DNA

1999 ◽  
Vol 112 (12) ◽  
pp. 2033-2041
Author(s):  
J.J. Ludtke ◽  
G. Zhang ◽  
M.G. Sebestyen ◽  
J.A. Wolff
Keyword(s):  
Active Transport ◽  
Nuclear Localization ◽  
Transport Process ◽  
Nuclear Transport ◽  
Passive Diffusion ◽  
Viral Gene ◽  
Nuclear Localization Signals ◽  
Size Limit ◽  
Cytosolic Extract ◽  
Active Transport Process

Although the entry of DNA into the nucleus is a crucial step of non-viral gene delivery, fundamental features of this transport process have remained unexplored. This study analyzed the effect of linear double stranded DNA size on its passive diffusion, its active transport and its NLS-assisted transport. The size limit for passive diffusion was found to be between 200 and 310 bp. DNA of 310–1500 bp entered the nuclei of digitonin treated cells in the absence of cytosolic extract by an active transport process. Both the size limit and the intensity of DNA nuclear transport could be increased by the attachment of strong nuclear localization signals. Conjugation of a 900 bp expression cassette to nuclear localization signals increased both its nuclear entry and expression in microinjected, living cells.

Total contents and net movements of magnesium in the rat uterus

1971 ◽  
Vol 220 (6) ◽  
pp. 2067-2067
Author(s):  
A. H. Moawad ◽  
E. E. Daniel
Keyword(s):  
Membrane Potential ◽  
Active Transport ◽  
Extracellular Space ◽  
Transport Process ◽  
Electrochemical Gradient ◽  
Rat Uterus ◽  
Active Transport Process

Page 75: A. H. Moawad and E. E. Daniel. "Total contents and net movements of magnesium in the rat uterus." Page 80, column 2, line 44, involving the calculation of Vm the answer to the equation, –0.067 V, should read, "–0.012 V." Page 80, column 2, lines 49–54 should read, "The calculated magnesium equilibrum potential is less than the observed membrane potential, which is about 0.050 V. Therefore, some of the tissue magnesium may be excluded by an active transport process against an electrochemical gradient or by loose binding in the extracellular space."

Ionic regulation of Na absorption in proximal colon: cation inhibition of electroneutral Na absorption

1987 ◽  
Vol 252 (1) ◽  
pp. G100-G108
Author(s):  
J. H. Sellin ◽  
R. De Soignie
Keyword(s):  
Linear Function ◽  
Active Transport ◽  
Transport Process ◽  
Proximal Colon ◽  
High Rate ◽  
Ionic Regulation ◽  
Diffusional Flux ◽  
Active Transport Process

Active Na absorption (JNanet) in rabbit proximal colon in vitro is paradoxically stimulated as [Na] in the bathing media is lowered with constant osmolarity. At 140 mM [Na]o, JNanet is -0.6 +/- 0.4 mueq X cm-2 X h-1, whereas at 50 mM [Na]o JNanet is 5.0 +/- 0.7 mueq X cm-2 X h-1, P less than 0.01. JNas----m is a linear function of [Na]o, suggesting a diffusional flux. JNam----s increases almost linearly from 0 to 50 mM [Na]o but then plateaus and actually decreases from 50 to 140 mM [Na]o, consistent with inhibition of an active transport process. Both lithium and Na are equally effective inhibitors of JNanet, whereas choline and mannitol do not block the high rate of JNanet observed in decreased [Na]o. Either gluconate or proprionate replacement of Cl inhibits JNanet. Removal of K or HCO3 does not alter Na absorption. JNanet at lowered [Na]o is electrically silent and is accompanied by increased Cl absorption; it is inhibited by 10(-3) M amiloride and 10(-3) M theophylline but not by 10(-4) M bumetanide. Epinephrine is equally effective at stimulating Na absorption at 50 and 140 mM [Na]; yohimbine does not inhibit JNanet at 50 mM [Na]o. Na gradient experiments are consistent with a predominantly serosal effect of the decreased [Na]o. These results suggest that Na absorption in rabbit proximal colon in vitro is stimulated by decreased [Na]; the effect is cation specific, both Na and Li blocking the stimulatory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Active transport of Fe59 by everted segments of rat duodenum

1960 ◽  
Vol 198 (3) ◽  
pp. 609-613 ◽  
Author(s):  
Eugene B. Dowdle ◽  
David Schachter ◽  
Harris Schenker
Keyword(s):  
Small Intestine ◽  
Active Transport ◽  
Transport Process ◽  
Transport Mechanism ◽  
Concentration Gradients ◽  
Active Transport Mechanism ◽  
Proximal Small Intestine ◽  
Rat Duodenum ◽  
Active Transport Process

Everted gut sacs prepared from segments of the proximal small intestine of rats transport Fe59 from the mucosal to the serosal surfaces against concentration gradients in vitro. The active transport mechanism is dependent upon oxidative metabolism and the generation of phosphate-bond energy, and is limited in capacity. The active transport process is maximal in the region of the small intestine immediately distal to the pylorus and diminishes with more distal segments of the gut. Addition of ascorbic acid to the incubation medium markedly increases the active transport of Fe59 in vitro.

Bioenergetics and mechanical actuation analysis with membrane transport experiments for use in biomimetic nastic structures

2006 ◽  
Vol 21 (8) ◽  
pp. 2058-2067 ◽  
Author(s):  
Luke Matthews ◽  
Vishnu Baba Sundaresan ◽  
Victor Giurgiutiu ◽  
Donald J. Leo
Keyword(s):  
Active Transport ◽  
Transport Process ◽  
Fluid Transport ◽  
Shape Change ◽  
Bilayer Membrane ◽  
Ion Channel Proteins ◽  
Polymeric Plate ◽  
Active Transport Process ◽  
Controllable Deformation ◽  
Pressure Changes

Nastic structures are synthetic constructs capable of controllable deformation and shape change similar to plant motility, designed to imitate the biological process of nastic movement found in plants. This paper considers the mechanics and bioenergetics of a prototype nastic structure system consisting of an array of cylindrical microhydraulic actuators embedded in a polymeric plate. Non-uniform expansion/contraction of the actuators in the array may yield an overall shape change resulting in structural morphing. Actuator expansion/contraction is achieved through pressure changes produced by active transport across a bilayer membrane. The active transport process relies on ion-channel proteins that pump sucrose and water molecules across a plasma membrane against the pressure gradient. The energy required by this process is supplied by the hydrolysis of adenosine triphosphate. After reviewing the biochemistry and bioenergetics of the active transport process, the paper presents an analysis of the microhydraulic actuator mechanics predicting the resulting displacement and output energy. Experimental demonstration of fluid transport through a protein transporter follows this discussion. The bilayer membrane is formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine lipids to support the AtSUT4 H+-sucrose cotransporter.

Uptake to adenosine in a marine bacterium is not an active transport process

FEBS Letters ◽  
1983 ◽  
Vol 160 (1-2) ◽  
pp. 31-36 ◽  
Author(s):  
Carmela Bengis-Garber
Keyword(s):  
Active Transport ◽  
Transport Process ◽  
Marine Bacterium ◽  
Active Transport Process

EQUILIBRATION OF SUCCINATE SOLUTIONS WITH ADAPTED AND UNADAPTED AZOTOBACTER CELLS

1954 ◽  
Vol 1 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Anna Maria Williams ◽  
P. W. Wilson
Keyword(s):  
Active Transport ◽  
Transport Process ◽  
External Solution ◽  
Intracellular Water ◽  
Permeability Changes ◽  
Rapid Diffusion ◽  
Active Transport Process

Sucrose-grown (unadapted) and succinate-grown (adapted) cells were mixed with various concentrations of succinate at 3 °C. under air and at 30 °C. under helium. The amount of succinate removed from the external solution by the cells was proportional to the concentration of succinate and did not differ significantly with the two types of cells. Although the data did not differentiate between equilibration with intracellular water and mere adsorption, they indicate that no change has occurred in the surface of the adapted cells to allow a more rapid diffusion of succinate across the osmotic barrier under nonmetabolic conditions. So far as can be determined by using masses of cells, any "permeability" changes during adaptation of the azotobacter cells to succinate must be connected with an active transport process associated with metabolism.

EFFECTS OF INTRA-ARTERIAL PERFUSIONS ON ELECTRICAL ACTIVITY AND ELECTROLYTE CONTENTS OF DOG SMALL INTESTINE

1965 ◽  
Vol 43 (4) ◽  
pp. 551-577 ◽  
Author(s):  
E. E. Daniel
Keyword(s):  
Small Intestine ◽  
Active Transport ◽  
Action Potentials ◽  
Transport Process ◽  
Longitudinal Muscle ◽  
Lithium Ion ◽  
Slow Waves ◽  
Sodium Ion ◽  
Intestinal Slow Waves ◽  
Active Transport Process

The mechanisms underlying the periodic depolarizations (slow waves) in longitudinal muscle of the small intestine were studied in vivo in dogs by means of intra-arterial perfusions of solutions with altered electrolyte concentrations or with added metabolic inhibitors. Perfusion of solutions containing reduced sodium, potassium, or chloride concentrations markedly altered electrolyte concentrations in intestinal muscle but did not necessarily alter intestinal slow waves seriously. However, when lithium ion was substituted for sodium ion serious depression of slow waves occurred. This was also found with ouabain, NaF, and Na2EDTA, substances which, like lithium, are believed to inhibit the active transport process directly. Iodoacetate and dinitrophenol had little depressant effect on intestinal slow waves in amounts sufficient to cause downhill ion movements. NaCN or 1,10-phenanthroline depressed slow waves, but the effect of NaCN was largely prevented by prior reserpinization of the dog. The depressant effects of lithium ion, ouabain, NaF, and Na2EDTA were diminished but not abolished by reserpinization. It was concluded that lower amounts of inhibitors of the active transport process abolished intestinal slow waves by causing the release of catecholamines from intrinsic nerve endings in the intestine. The released catecholamines then depressed slow waves. In higher amounts, inhibitors of the active transport process depressed intestinal slow waves by a direct action, unaffected by reserpinization. Intestinal slow waves were therefore postulated to originate from the oscillatory activity of an electrogenic sodium pump.Perfusates with elevated sodium or potassium concentration initiated action potentials in intestinal longitudinal muscle. These action potentials were blocked by atropine and hexamethonium. In reserpinized animals, Na2EDTA or large amounts of ouabain also initiated action potentials which were stopped or prevented by atropine. It was postulated that all these procedures caused acetylcholine release from intrinsic parasympathetic nerves and that the common mechanism was displacement of mediator by net entrance of sodium ion. This same mechanism may also have accounted for the release of catecholamines from intrinsic sympathetic nerves mentioned above.

Evidence for active and passive urate transport in the rat proximal tubule

1981 ◽  
Vol 240 (2) ◽  
pp. F90-F93
Author(s):  
E. J. Weinman ◽  
H. O. Senekjian ◽  
S. C. Sansom ◽  
D. Steplock ◽  
A. Sheth ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Active Transport ◽  
Transport Process ◽  
Permeability Coefficient ◽  
Electrical Potential ◽  
Electrical Potential Difference ◽  
Passive Permeability ◽  
Peritubular Capillaries ◽  
Active Transport Process ◽  
Rat Proximal Tubule

Studies utilizing the technique of simultaneous microperfusion of peritubular capillaries and tubular lumen of the proximal tubule of the rat were performed to determine if the absorption of urate was an active transport process and to determine the passive permeability coefficient for urate. When radioactive urate of equal specific activity and concentration was present in both perfusion solutions, the ratio of collected to initial concentrations of urate in the luminal perfusate (CO/CI) was 0.71 +/- 0.02. This gradient was higher than that predicted at equilibrium from the electrical potential difference determined in the in vitro perfused rabbit proximal tubule. The addition of para-chloromercuribenzoate (PCMB) to both solutions resulted in a significantly higher CO/CI of 0.90 +/- 0.02. This latter value is closer to the value predicted at electrochemical equilibrium. In separate studies, the unidirectional fluxes of urate were determined in the presence of PCMB. The calculated passive permeability coefficient averaged approximately 0.94 pmol . min-1 . mm-1 . mM-1 and was equal in both directions. These results indicate that in the rat proximal tubule urate absorption is an active transport process. In addition, there exists a passive permeation pathway for urate movement out of and into the proximal tubule.

scholarly journals Dinitrophenyl glutathione efflux from human erythrocytes is primary active ATP-dependent transport

1986 ◽  
Vol 238 (2) ◽  
pp. 443-449 ◽  
Author(s):  
E F LaBelle ◽  
S V Singh ◽  
S K Srivastava ◽  
Y C Awasthi
Keyword(s):  
Energy Source ◽  
Membrane Potential ◽  
Active Transport ◽  
Concentration Gradient ◽  
Transport Process ◽  
Human Erythrocytes ◽  
Dependent Transport ◽  
Active Transport Process ◽  
Inside Out ◽  
Primary Active Transport

Dinitrophenyl S-glutathione is accumulated by inside-out vesicles made from human erythrocytes in a process totally dependent on ATP and Mg2+. The vesicles were shown to accumulate dinitrophenyl S-glutathione against a concentration gradient. The vesicles were able to concentrate this glutathione derivative even in the absence of membrane potential. This indicated that the ATP-dependent uptake of dinitrophenyl S-glutathione by inside-out vesicles represented an active transport process. Neither extravesicular EGTA nor intravesicular ouabain inhibited the transport process, indicating that neither the Ca2+-ATPase nor the Na+, K+-ATPase were involved. These results indicated that dinitrophenyl S-glutathione uptake by inside-out vesicles probably represented primary active transport. The uptake of dinitrophenyl S-glutathione was a linear function of time (up to 5 h) and vesicle protein. The rate of uptake was optimal between pH 7.0 and 8.0 and at 37 degrees C. The Km values determined for dinitrophenyl S-glutathione and ATP were 0.29 mM and 1 mM, respectively. The transport process was completely inhibited by vanadate and by p-hydroxymercuribenzene sulphonate and inhibited to a lesser extent by N-ethylmaleimide. GTP could efficiently substitute for ATP as an energy source for the transport process, but CTP and UTP were comparatively much less effective.

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