scholarly journals An analog to digital converter creates nuclear localization pulses in yeast calcium signaling

2018 ◽  
Author(s):  
Ian S Hsu ◽  
Bob Strome ◽  
Sergey Plotnikov ◽  
Alan M Moses
Keyword(s):  
Nuclear Localization ◽  
Calcium Concentration ◽  
Nuclear Transport ◽  
Analog To Digital ◽  
Signaling Systems ◽  
Analog Signals ◽  
Calcium Stress ◽  
Molecule Dynamics ◽  
Simple Stochastic Model ◽  
External Calcium

AbstractSeveral examples of transcription factors that show stochastic, unsynchronized pulses of nuclear localization have been described. Here we show that under constant calcium stress, nuclear localization pulses of the transcription factor Crz1 follow stochastic variations in cytoplasmic calcium concentration. We find that the size of the stochastic calcium pulses is positively correlated with the number of subsequent Crz1 pulses. Based on our observations, we propose a simple stochastic model of how the signaling pathway converts a constant external calcium concentration into a digital number of Crz1 pulses in the nucleus, due to the time delay from nuclear transport and the stochastic decoherence of individual Crz1 molecule dynamics. We find support for several additional predictions of the model and conclude that stochastic input to nuclear transport may produce digital responses to analog signals in other signaling systems.

SELF-TIMED ARCHITECTURE FOR MASKED SUCCESSIVE APPROXIMATION ANALOG-TO-DIGITAL CONVERSION

2007 ◽  
Vol 16 (01) ◽  
pp. 1-14
Author(s):  
TASKIN KOCAK ◽  
GEORGE R. HARRIS ◽  
RONALD F. DEMARA
Keyword(s):  
Successive Approximation ◽  
Cmos Technology ◽  
Digital Systems ◽  
Digital Converter ◽  
Digital Conversion ◽  
Analog To Digital ◽  
Analog Signals ◽  
Analog To Digital Conversion ◽  
Null Convention Logic ◽  
The One

In this paper, a novel architecture for self-timed analog-to-digital conversion is presented and designed using the NULL Convention Logic (NCL) paradigm. This analog-to-digital converter (ADC) employs successive approximation and a one-hot encoded masking technique to digitize analog signals. The architecture scales readily to any given resolution by utilizing the one-hot encoded scheme to permit identical logical components for each bit of resolution. The four-bit configuration of the proposed design has been implemented and assessed via simulation in 0.18-μm CMOS technology. Furthermore, the ADC may be interfaced with either synchronous or four-phase asynchronous digital systems.

scholarly journals Expressed Na channel clones differ in their sensitivity to external calcium concentration

1992 ◽  
Vol 62 (1) ◽  
pp. 37-40 ◽  
Author(s):  
M. Chahine ◽  
L.Q. Chen ◽  
R.G. Kallen ◽  
R.L. Barchi ◽  
R. Horn
Keyword(s):  
Calcium Concentration ◽  
Na Channel ◽  
External Calcium

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.

Nuclear transport of the U2 snRNP-specific U2B'' protein is mediated by both direct and indirect signalling mechanisms

1994 ◽  
Vol 107 (7) ◽  
pp. 1807-1816 ◽  
Author(s):  
C. Kambach ◽  
I.W. Mattaj
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Localization Signal ◽  
Nuclear Transport ◽  
U2 Snrna ◽  
Central Segment ◽  
U2 Snrnp ◽  
U1 Snrnp ◽  
Localization Signal ◽  
Protein Amino Acids

Experiments investigating the nuclear import of the U2 snRNP-specific B'' protein (U2B'') are presented. U2B'' nuclear transport is shown to be able to occur independently of binding to U2 snRNA. The central segment of the protein (amino acids 90–146) encodes an unusual nuclear localization signal (NLS) that is related to that of the U1 snRNP-specific A protein. However, nuclear import of U2B'' does not depend on this NLS. Sequences in the N-terminal RNP motif of the protein are sufficient to direct nuclear transport, and evidence is presented that the interaction of U2B'' with the U2A' protein mediates this effect. This suggests that U2B'' can ‘piggy-back’ to the nucleus in association with U2A’, and thus be imported to the nucleus by two different mechanisms. U2A' nuclear transport, on the other hand, can occur independently of both U2B'' binding and of U2 snRNA.

The resting membrane potential of Drosophila melanogaster larval muscle depends strongly on external calcium concentration

2010 ◽  
Vol 56 (3) ◽  
pp. 304-313 ◽  
Author(s):  
Jacob L. Krans ◽  
Karen D. Parfitt ◽  
Kristin D. Gawera ◽  
Patricia K. Rivlin ◽  
Ronald R. Hoy
Keyword(s):  
Drosophila Melanogaster ◽  
Membrane Potential ◽  
Calcium Concentration ◽  
Resting Membrane Potential ◽  
Larval Muscle ◽  
External Calcium

The Effect of Changed Extracellular Calcium and Sodium Concentration on the Electroretinogram of the Crayfish Retina

1980 ◽  
Vol 35 (3-4) ◽  
pp. 308-318 ◽  
Author(s):  
H. Stieve ◽  
I. Claßen-Linke
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Calcium Concentration ◽  
Light Adaptation ◽  
Sodium Concentration ◽  
Strong Increase ◽  
Calcium Stores ◽  
Half Time ◽  
Astacus Leptodactylus ◽  
External Calcium

Abstract The electroretinogram (ERG) of the isolated retina of the crayfish Astacus leptodactylus evoked by strong 10 ms light flashes at constant 5 min intervals was measured while the retina was continuously superfused with various salines which differed in Ca2+ -and Na+ -concentrations. The osmotic pressure of test- and reference-saline was adjusted to be identical by adding sucrose. Results: 1. Upon raising the calcium-concentration of the superfusate in the range of 20-150 mmol/l (constant Na+ -concentration: 208 mmol/l) the peak amplitude hmax and the half time of decay t2 of the ERG both decrease gradually up to about 50% in respect to the corresponding value in reference saline. 2. The recovery of the ERG due to dark adaptation following the “weakly light adapted state” is greatly diminished in high external [Ca2+]ex. 3. Lowering the external calcium-concentration (10 →1 mmol/l) causes a small increase in hmax and a strong increase of the half time of decay t2 (about 180%). Upon lowering the calcium concentration of the superfusate to about 1 nmol/l by 1 mmol/l of the calcium buffer EDTA, a slowly augmenting diminution of the ERG height hm SLX occurs. How­ever, a strong retardation of the falling phase of the ERG characterized by an increase in t2 occurs quickly. Even after 90 min stay in the low calcium saline the retina is still not inexcitable; hmax is 5 - 10% of the reference value. The diminution of hmax occurs about six-fold faster when the buffer concentration is raised to 10 mmol/l EDTA. 4. Additional lowering of the Na+ -concentration (208 →20.8 mmol/l) in a superfusate with a calcium concentration raised to 150 mmol/l causes a strong reduction of the ERG amplitude hmax to about 10%. 5. In a superfusate containing 1 nmol/l calcium such lowering of the sodium concentration (208 → 20.8 mmol/l) causes a diminution of the ERG height to about 40% and the shape of the ERG to become polyphasic; at least two maxima with different time to peak values are observed. Interpretation: 1. The similarity of effects, namely raising external calcium concentration and light adaptation on the one hand and lowering external calcium and dark adaptation on the other hand may indicate that the external calcium is acting on the adaptation mechanism of the photoreceptor cells, presumably by influencing the intracellular [Ca2+]. 2. The great tolerance of the retina against Ca2+ -deficiency in the superfusate might be effected by calcium stores in the retina which need high Ca2+ -buffer concentrations in the superfusate to become exhausted. 3. In contrast to the Limulus ventral nerve photoreceptor there does not seem to be an antagonis­ tic effect of sodium and calcium in the crayfish retina on the control of the light channels. 4. The crayfish receptor potential seems to be composed of at least two different processes. Lowering calcium-and lowering external sodium-concentration both diminish the height and change the time course of the two components to a different degree. This could be caused by in­ fluencing the state of adaptation and thereby making the two maxima separately visible.

Effects of Ca2+ and catecholamines on the guinea pig atrium action potential plateau

1977 ◽  
Vol 233 (2) ◽  
pp. H203-H210
Author(s):  
R. B. Robinson ◽  
W. W. Sleator
Keyword(s):  
Guinea Pig ◽  
Calcium Concentration ◽  
Potassium Conductance ◽  
Slow Inward Current ◽  
Activation Process ◽  
Action Potential Plateau ◽  
Guinea Pig Atrium ◽  
Opposing Effects ◽  
Guinea Pig Atria ◽  
External Calcium

The activation process in isolated electrically driven guinea pig atria was studied by means of simultaneous microelectrode and tension recording. Reducing external calcium from 2.5 to 1.25 mM prolonged the plateau but further reduction of calcium shortened it. Progressively increasing doses of the calcium antagonist D600 (up to 1.4 micrometer), however, monotonically decreased plateau duration. Either protocol monotonically decreased steady-state tension, but with markedly different effects on the restitution relation. Epinephrine, and to a lesser extent isoproterenol, restored plateau duration after exposure to either a calcium-free or D600-containing solution, but only the isoproterenol effect was propranolol sensitive. Addition of calcium chelators enhanced rather than prevented the effect of epinephrine on plateau duration in a calcium-free solution, extending the plateau duration to more than 3 times normal in some cases. These results are explained in terms of two opposing effects of a change in calcium concentration on plateau formation, one action being through the slow inward current and the second through a shift in a calcium dependence of the inward-rectifying, potassium conductance system.

Invariance of Stoichiometry of the Sarcoplasmic Reticulum Calcium Pump at Physiological Calcium Concentrations – a Reevaluation

1985 ◽  
Vol 40 (7-8) ◽  
pp. 571-575 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Andrea Migala
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Level ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Atp Hydrolysis ◽  
Calcium Pump ◽  
Oxalate Precipitation ◽  
Sarcoplasmic Reticulum Calcium ◽  
Internal Calcium ◽  
External Calcium

Abstract The decline of the transport ratio of the sarcoplasmic calcium pump observed in a recent study (A. results from the retardation of calcium oxalate precipitation at low calcium/protein ratios. The prevailing high internal calcium level supports a rapid calcium backflux and a compensatory ATP hydrolysis during net calcium uptake which reduces the transport ratio. Yet, the determined calcium back­ flux does not fully account for the decline of the transport ratio. A supposed modulation of the stoichiometry of the pump by external calcium (0.1 μм) is at variance with results of previous studies showing a constant transport ratio of two in the same calcium concentration range.

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