The role of Ca2+ in deflection-induced excitation of motile, mechanoresponsive balancer cilia in the ctenophore statocyst.

1997 ◽  
Vol 200 (11) ◽  
pp. 1593-1606 ◽  
Author(s):  
B Lowe
Keyword(s):  
Beat Frequency ◽  
Mnemiopsis Leidyi ◽  
Directional Sensitivity ◽  
Free Medium ◽  
Ciliary Beating ◽  
Graded Responses ◽  
Neural Input ◽  
High K ◽  
Pleurobrachia Pileus

Motile, mechanoresponsive cilia (balancers) in ctenophore statocysts, like vertebrate hair cells, are excited or inhibited depending upon the direction in which they are deflected. Balancers, however, may become either excited (beat rapidly) or inhibited (beat slowly) by deflection in the same direction, depending on the sign of ctenophore geotaxis (positive or negative). The beat frequency of many cilia is controlled by concentrations of Ca2+, membrane potential and neural input. How these factors affect deflection-induced ciliary beating in balancers was investigated. Deflection-induced excitation of balancers in whole Mnemiopsis leidyi larvae and dissected adult (Mnemiopsis leidyi, Pleurobrachia pileus) statocysts was reversibly inhibited by the Ca2+ channel inhibitors Co2+, Mg2+, Ni2+, and Mn2+. Deflection-induced excitation in balancers of isolated adult M. leidyi balancer groups was also inhibited by Co2+ or by Ca(2+)-free medium. Isolated balancer group cilia, like balancer cilia of intact ctenophores, exhibited responses to either sign of geotaxis and graded responses to deflection. Isolated balancers that were chemically depolarized in high-[K+], Ca(2+)-free medium were excited by local application of Ca2+ onto the ciliary bases, but not onto the cell bases or the ciliary tips. It is proposed that deflection-induced excitation of balancers is due to influx of Ca2+ through stretch- and voltage-activated channel activity. The sign of geotaxis of whole larvae and dissected adult statocysts was switched by electrical stimulation. Thus, neural input may participate in reversing the directional sensitivity of balancer cells.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

scholarly journals PKA induces Ca2+ release and enhances ciliary beat frequency in a Ca2+-dependent and -independent manner

1998 ◽  
Vol 275 (3) ◽  
pp. C790-C797 ◽  
Author(s):  
Alex Braiman ◽  
Orna Zagoory ◽  
Zvi Priel
Keyword(s):  
Beat Frequency ◽  
Ciliary Beat Frequency ◽  
Ciliary Activity ◽  
Experimental Conditions ◽  
Independent Manner ◽  
Ciliary Beating ◽  
Independent Mechanism ◽  
Intracellular Ca ◽  
Ciliary Beat

The intent of this work was to evaluate the role of cAMP in regulation of ciliary activity in frog mucociliary epithelium and to examine the possibility of cross talk between the cAMP- and Ca2+-dependent pathways in that regulation. Forskolin and dibutyryl cAMP induced strong transient intracellular Ca2+ concentration ([Ca2+]i) elevation and strong ciliary beat frequency enhancement with prolonged stabilization at an elevated plateau. The response was not affected by reduction of extracellular Ca2+concentration. The elevation in [Ca2+]iwas canceled by pretreatment with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid-AM, thapsigargin, and a phospholipase C inhibitor, U-73122. Under those experimental conditions, forskolin raised the beat frequency to a moderately elevated plateau, whereas the initial strong rise in frequency was completely abolished. All effects were canceled by H-89, a selective protein kinase A (PKA) inhibitor. The results suggest a dual role for PKA in ciliary regulation. PKA releases Ca2+ from intracellular stores, strongly activating ciliary beating, and, concurrently, produces moderate prolonged enhancement of the beat frequency by a Ca2+-independent mechanism.

scholarly journals The Role of Calcium in the Regulation of the Steady-State Levels of Sodium and Potassium in the HeLa Cell

1967 ◽  
Vol 50 (4) ◽  
pp. 781-792 ◽  
Author(s):  
Gene A. Morrill ◽  
Elliott Robbins
Keyword(s):  
Steady State ◽  
Free Medium ◽  
Na Transport ◽  
Cell Water ◽  
High K ◽  
Spinner Culture ◽  
Free Choline ◽  
Steady State Levels ◽  
Sodium And Potassium

Studies on HeLa cells in spinner culture at pH 7.0 and 37° have shown that [Na]i decreased and [K]i increased with increasing [Ca]o. In Na-free (choline) medium [K]i remained high whether or not Ca was present in the medium. [Na]i and [K]i approached a new steady state within 1 min after transfer to Ca-free medium and returned to the initial values within 15 min upon readdition of Ca. 40% of the cell Ca exchanged within 1 min followed by a slow exchange of the remaining Ca over several hours. [Ca]i increased with decreasing [Na]o but was independent of [K]o. Equimolar Mg did not substitute for Ca in maintaining low [Na]i and high [K]i. Under steady-state conditions about 50% of the cell Na exchanged in accordance with a single rate constant. The initial Na influx was 270, 100, and 2.5 µM/liter of cell water/sec for 0, 0.10, and 1.0 mM [Ca]o, respectively. When Na transport was inhibited with strophanthidin and [Na]i and [K]i allowed to reach a steady state, Na influx was more rapid for cells incubated in Ca-free medium than for cells incubated in medium containing 1.0 mM Ca. These results suggest that Ca competes with Na at the cell membrane and thus controls the passive diffusion of Na into the cell.

scholarly journals An Outer Arm Dynein Conformational Switch Is Required for Metachronal Synchrony of Motile Cilia in Planaria

2010 ◽  
Vol 21 (21) ◽  
pp. 3669-3679 ◽  
Author(s):  
Panteleimon Rompolas ◽  
Ramila S. Patel-King ◽  
Stephen M. King
Keyword(s):  
Beat Frequency ◽  
Feedback System ◽  
Ciliary Beat Frequency ◽  
Conformational Switch ◽  
Ciliary Beating ◽  
Similar Phenotype ◽  
Motile Cilia ◽  
Metachronal Waves ◽  
Mechanical Feedback

Motile cilia mediate the flow of mucus and other fluids across the surface of specialized epithelia in metazoans. Efficient clearance of peri-ciliary fluids depends on the precise coordination of ciliary beating to produce metachronal waves. The role of individual dynein motors and the mechanical feedback mechanisms required for this process are not well understood. Here we used the ciliated epithelium of the planarian Schmidtea mediterranea to dissect the role of outer arm dynein motors in the metachronal synchrony of motile cilia. We demonstrate that animals that completely lack outer dynein arms display a significant decline in beat frequency and an inability of cilia to coordinate their oscillations and form metachronal waves. Furthermore, lack of a key mechanosensitive regulatory component (LC1) yields a similar phenotype even though outer arms still assemble in the axoneme. The lack of metachrony was not due simply to a decrease in ciliary beat frequency, as reducing this parameter by altering medium viscosity did not affect ciliary coordination. In addition, we did not observe a significant temporal variability in the beat cycle of impaired cilia. We propose that this conformational switch provides a mechanical feedback system within outer arm dynein that is necessary to entrain metachronal synchrony.

Time-dependent increase in Ca2+ influx in rabbit abdominal aorta: role of Na-Ca exchange

1993 ◽  
Vol 265 (5) ◽  
pp. C1325-C1331 ◽  
Author(s):  
M. A. Khoyi ◽  
R. A. Bjur ◽  
D. P. Westfall
Keyword(s):  
Abdominal Aorta ◽  
Sodium Pump ◽  
Time Dependent ◽  
Free Medium ◽  
Phorbol Dibutyrate ◽  
45Ca Fluxes ◽  
High K

Exposure of the rabbit abdominal aorta to the combination of high K+ and norepinephrine resulted in a time-dependent increase in the rate of 45Ca influx and 45Ca and 22Na content over that observed after stimulation with either K+ or norepinephrine alone. The increase in 45Ca influx, but not the increase in 22Na content, was extracellular Ca2+ (Cao2+) dependent. This time-dependent increase in 45Ca influx was prevented by incubating the tissue in Na(+)-free medium. Nifedipine inhibited both the initial depolarization-induced 45Ca influx and time-dependent increase in 45Ca influx and 22Na content. The effect of nifedipine on time-dependent fluxes was prevented by ouabain. Phorbol dibutyrate mimicked the effects of norepinephrine on 22Na retention and 45Ca fluxes. The effects of phorbol dibutyrate and norepinephrine were not additive. It is concluded that, in rabbit abdominal aorta, norepinephrine plus K+ causes 22Na retention (possibly through inhibition of the sodium pump) and a Cao(2+)- and intracellular Na+ (Nai+)-dependent increase in 45Ca influx. This latter effect is possibly the result of increased Nai(+)-Cao2+ exchange.

scholarly journals The role of ATP in the differential ability of Sr2+ to trigger Ca2+ oscillations in mouse and human eggs

2021 ◽  
Author(s):  
Anna Storey ◽  
Khalil Elgmati ◽  
Yisu Wang ◽  
Paul Knaggs ◽  
Karl Swann
Keyword(s):  
Phospholipase C ◽  
Egg Activation ◽  
Apparent Difference ◽  
Free Medium ◽  
Inositol 1 ◽  
Atp Levels ◽  
Mature Mouse ◽  
Differential Ability ◽  
Mouse Eggs

Abstract At fertilization in mice and humans, the activation of the egg is caused by a series of repetitive Ca2+ oscillations which are initiated by phospholipase-C(zeta)ζ that generates inositol-1-4-5-trisphophate (InsP3). Ca2+ oscillations and egg activation can be triggered in mature mouse eggs by incubation in Sr2+ containing medium, but this does not appear to be effective in human eggs. Here we have investigated the reason for this apparent difference using mouse eggs, and human eggs that failed to fertilize after IVF or ICSI. Mouse eggs incubated in Ca2+-free, Sr2+-containing medium immediately underwent Ca2+ oscillations but human eggs consistently failed to undergo Ca2+ oscillations in the same Sr2+ medium. We tested the InsP3-receptor (IP3R) sensitivity directly by photo-release of caged InsP3 and found that mouse eggs were about 10 times more sensitive to InsP3 than human eggs. There were no major differences in the Ca2+ store content between mouse and human eggs. However, we found that the ATP concentration was consistently higher in mouse compared to human eggs. When ATP levels were lowered in mouse eggs by incubation in pyruvate-free medium, Sr2+ failed to cause Ca2+ oscillations. When pyruvate was added back to these eggs, the ATP levels increased and Ca2+ oscillations were induced. This suggests that ATP modulates the ability of Sr2+ to stimulate IP3R-induced Ca2+ release in eggs. We suggest that human eggs may be unresponsive to Sr2+ medium because they have a lower level of cytosolic ATP.

Role of extracellular calcium and calmodulin in prolactin secretion induced by hyposmolarity, thyrotropin-releasing hormone, and high K+ in GH4C1 cells

1990 ◽  
Vol 123 (2) ◽  
pp. 218-224 ◽  
Author(s):  
Xiangbing Wang ◽  
Noriyuki Sato ◽  
Monte A. Greer ◽  
Susan E. Greer ◽  
Staci McAdams
Keyword(s):  
Smooth Muscle ◽  
Muscle Relaxant ◽  
Prolactin Secretion ◽  
Thyrotropin Releasing Hormone ◽  
Dependent Manner ◽  
Cell Toxicity ◽  
High K ◽  
Dose Dependent ◽  
Smooth Muscle Relaxant

Abstract. The mechanism by which 30% medium hyposmolarity induces PRL secretion by GH4C1 cells was compared with that induced by 100 nmol/l TRH or 30 mmol/l K+. Removing medium Ca2+, blocking Ca2+ channels with 50 μmol/l verapamil, or inhibiting calmodulin activation with 20 μmol/l trifluoperazine, 10 μmol/l chlorpromazine or 10 μmol/l pimozide almost completely blocked hyposmolarity-induced secretion. The smooth muscle relaxant, W-7, which is believed relatively specific in inhibiting the Ca2+-calmodulin interaction, depressed hyposmolarity-induced PRL secretion in a dose-dependent manner (r = −0.991, p<0.01 ). The above drugs also blocked or decreased high K+-induced secretion, but had much less effect on TRH-induced secretion. Secretion induced by TRH, hyposmolarity, or high K+ was optimal at pH 7.3-7.65 and was significantly depressed at pH 6.0 or 8.0, indicating that release of hormone induced by all 3 stimuli is due to an active cell process requiring a physiologic extracellular pH and is not produced by nonspecific cell toxicity. The data suggest hyposmolarity and high K+ may share some similarities in their mechanism of stimulating secretion, which is different from that of TRH.

scholarly journals Factors affecting the permeability of isolated fat-cells from the rat to [42K]potassium and [36Cl]chloride ions

1970 ◽  
Vol 117 (3) ◽  
pp. 615-621 ◽  
Author(s):  
M. C. Perry ◽  
C. N. Hales
Keyword(s):  
Initial Phase ◽  
Chloride Ions ◽  
Fat Cells ◽  
Adrenocorticotrophic Hormone ◽  
Isolated Fat Cells ◽  
Free Medium ◽  
Fat Cell ◽  
Factors Affecting ◽  
Exchange Diffusion ◽  
High K

1. The effluxes of 42K+ and 36Cl− from isolated fat-cells from the rat were studied under a variety of conditions known to affect the metabolism of the cells. 2. 42K+ efflux from isolated fat cells was increased in a Na+-free–high-K+ medium and decreased in a K+-free medium. The existence of K+ exchange diffusion across the fat-cell membrane is suggested. 3. 36Cl− efflux from isolated fat-cells was decreased when the Cl− component of the wash medium was replaced by acetate. The basal 36Cl− efflux is suggested to be partly by Cl− exchange diffusion and partly in company with a univalent cation. 4. A variety of lipolytic stimuli, adrenaline, adrenocorticotrophic hormone, N-6,O-2′-dibutyryladenosine cyclic 3′:5′-monophosphate and theophylline, increased 42K+ efflux from isolated fat-cells. The adrenaline stimulation was biphasic; an initial, rapid and transient increase in 42K+ loss from the fat-cells was followed by a slower, more prolonged, increase in 42K+ efflux. The initial phase was inhibited by phentolamine but not by propranolol. 5. Insulin increased 42K+ efflux only after preincubation with the cells.

scholarly journals The Role of Sequestrene 138 in Highbush Blueberry (Vaccinium corymbosum L.) Micropropagation

HortScience ◽  
2018 ◽  
Vol 53 (10) ◽  
pp. 1487-1493 ◽  
Author(s):  
Doina Clapa ◽  
Claudiu Bunea ◽  
Orsolya Borsai ◽  
Adela Pintea ◽  
Monica Hârța ◽  
...  
Keyword(s):  
Culture Media ◽  
Iron Concentration ◽  
Vaccinium Corymbosum ◽  
Carotenoid Content ◽  
Free Medium ◽  
Axillary Shoots ◽  
Different Types ◽  
The Media ◽  
Dark Green

The current research was carried out to investigate the effects of iron source in the culture media for Vaccinium corymbosum L. ʻBluerayʼ, ʻDukeʼ, and ʻPatriotʼ cultivars grown on five different types of medium (Woody Plant Medium supplemented with 1.0 mg·L−1 zeatin and 0, 25, 50, 75, and 100 mg·L−1 Sequestrene 138). After 10 weeks of culture, seven physiological parameters were measured, such as the number and length of axillary shoots, rooting and acclimatization percentage, as well as chlorophyll (a, b, a/b) and carotenoid content of the leaves. Adding Sequestrene 138 to the culture media led to a slight decrease of the proliferation rate but increased the length of the shoots. The chlorophyll and carotenoid content in all of the three cultivars was considerably increased as the iron concentration of the media increased. The shoots developed on the Sequestrene 138–free medium were chlorotic and short, whereas at different concentrations of iron in the culture medium the shoots were dark green and vigorous, providing a greater acclimatization success than those grown in iron-free medium.

Differential effects of UTP, ATP, and adenosine on ciliary activity of human nasal epithelial cells

2001 ◽  
Vol 280 (6) ◽  
pp. C1485-C1497 ◽  
Author(s):  
Diane M. Morse ◽  
Jennifer L. Smullen ◽  
C. William Davis
Keyword(s):  
Epithelial Cells ◽  
Beat Frequency ◽  
Ciliary Beat Frequency ◽  
Ciliary Activity ◽  
Maximal Effect ◽  
Ciliary Beating ◽  
Mediated Effects ◽  
Human Nasal Epithelium ◽  
Human Nasal Epithelial Cells ◽  
Sustained Responses

The purinergic regulation of ciliary activity was studied using small, continuously superfused explants of human nasal epithelium. The P2Y2 purinoceptor (P2Y2-R) was identified as the major purinoceptor regulating ciliary beat frequency (CBF); UTP (EC50 = 4.7 μM), ATP, and adenosine-5′- O-(3-thiotriphosphate) elicited similar maximal responses, approximately twofold over baseline. ATP, however, elicited a post-peak sustained plateau in CBF (1.83 ± 0.1-fold), whereas the post-peak CBF response to UTP declined over 15 min to a low-level plateau (1.36 ± 0.16-fold). UDP also stimulated ciliary beating, probably via P2Y6-R, with a maximal effect approximately one-half that elicited by P2Y2-R stimulation. Not indicated were P2Y1-R-, P2Y4-R-, or P2Y11-R-mediated effects. A2B-receptor agonists elicited sustained responses in CBF approximately equal to those from UTP/ATP [5′-( N-ethylcarboxamido)adenosine, EC50 = 0.09 μM; adenosine, EC50 = 0.7 μM]. Surprisingly, ADP elicited a sustained stimulation in CBF. The ADP effect and the post-peak sustained portion of the ATP response in CBF were inhibited by the A2-R antagonist 8-( p-sulfophenyl)theophylline. Hence, ATP affects ciliary activity through P2Y2-R and, after an apparent ectohydrolysis to adenosine, through A2BAR.

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