ISSN 00124966, Doklady Biological Sciences, 2015, Vol. 460, pp. 64–67. © Pleiades Publishing, Ltd., 2015. Original Russian Text © D.A. Nikishin, S.V. Kremnyov, N.S. Glagoleva, 2015, published in Doklady Akademii Nauk, 2015, Vol. 460, No. 6, pp. 729–732.
CELL BIOLOGY
Role of Gap Junctions and Mechanosensitive Ion Channels in the Mechanisms of Growth Pulsations of Gonothyraea loveni D. A. Nikishina, b, S. V. Kremnyova, and N. S. Glagolevaa Presented by Academician S.A. Lukyanov August 28, 2014 Received August 28, 2014
DOI: 10.1134/S0012496615010184
dermal cells, gastrodermal cells are always extremely vacuolated, and their movements are not accompa nied by changes in volume. The gastrodermal compo nent of growth pulsation includes changes in the shape of the gastrodermal tube: the tube narrowing and elon gation (probably, through contraction of the annular muscle processes of the epithelial–muscular gastro dermal cells) alternate with the tube thickening and shortening [5]. Thus, growth pulsation is a result of coordinated movements of epidermal and gastroder mal cells: the gastroderm is involved in pushing the apex and stretching of young perisarc; the epidermal cell movements ensure fixation of a amount of growth. What remains unclear is how cell movements are coordinated during pulsating growth. Changes in cell orientation have been noticed to spread wavelike in the proximal–distal direction. Only at the stage of short ening do all cells begin to move almost synchronously [6]. In epithelia, cell communications can take place via the gap junctions by means of depolarization or signaling molecules. The gap junction proteins, innex ines, have been described in invertebrates, including Coelenterata [8]. Cell movements during growth pul sation are most likely coordinated via the gap junc tions, which explains the proximal–distal waves of cell movements. On the other hand, during the retraction stage, triggering of cell movements occurs probably due to activation of the mechanosensitive ion channels [1], as it happens in the case of directed movements of keratinocytes [9]. Here, we studied the mechanisms underlying coor dination of cell movements during growth pulsation of hydroid polyps and; the stolon tips served as the sim plest system, because it is not exposed to morphogen esis and is methodically convenient. The study has been conducted on the Pertsov White Sea Biological Station, Moscow State University. Col onies of Gonothyraea loveni (Allman, 1859) were col lected on the Eremeevsky Rapids (66°33′06.8′′ N, 33°06′57.2′′ E). The shoot fragments placed on glass slides were planted in an aerated aquarium and culti
Growth and morphogenesis of all rudiments of colonial hydroid polyps occurs due to pulsation of a specialized apical portion of the colony body, the growing tips. Growth pulsation is a result of recurrent proximal–distal waves of contractions and relaxations of epi and gastrodermal cells. There is no prolifera tion within the growing tips and growth is exclusively due to cell movements [1]. The shape of a developing rudiment is directly dependent on the growth pulsa tion parameters in the course of natural or experimen tal apical growth [2]. The mechanisms underlying growth pulsation of hydroid polyps are of interest because hydroid polyps represent a simple and con trollable model of the epithelial morphogenesis, which is widely involved in organogenesis of many animals, including mammals. The cellular mechanisms of growth pulsation in hydroid polyps are well described in studies by Belousov [1–3] and Kosevich [5]. While growing, the hydroid tips have successive rhythmic cell movements leading to a gradual slight amount of growth after each cycle. This phenomenon is accompanied by periodic changes in the volume and orientation of epidermal cells by means of the osmosis–contractile mechanism. An increase in epidermal cell volume occurs at the stage of extension because of accumulation of volumi nous vacuoles; after vacuole fusion, they are poured out into the environment to reduce the cell volume at the stage of retraction [6, 7]. At the same time, the proximal–distal shifts of cell apical surfaces take place, which makes it possible to start the next cycle of cell movements from a new point. As demonstrated by indi rect methods, the retraction phase is accompanied by cell membrane depolarization, as well as by an increase in the cytoplasmic calcium concentration [2, 7]. Unlike epi
a
Moscow State University, Moscow, 119234 Russia; email; [email protected] b Kol’tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 117808 Russia 64
ROLE OF GAP JUNCTIONS AND MECHANOSENSITIVE ION CHANNELS
65
(a)
Amount of growth, μm 200 Control Carbenoxolon 100 μM 150
Washing
100
50
0
20
40
60
80
100
120 Time, min
80
100
120 Time, min
(b)
Amount of growth, μm 200 Control Gadolinium 50 μM 150
Washing
100
50
0
20
40
60
Fig. 1. The growth pulsation curves of G. loveni stolon tips under the influence of the agents blocking either (a) gap junctions (car benoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)).
vated at room temperature (20–22°С) and daily fed with Artemia nauplii. The young colonies grown for three days consisted of the maternal shoot, stolon, and one or two new shoots. Wellgrowing stolon tips with out anomalies were used in the experiments. The sto lon tip growth was examined using an MBI1 (LOMO, Soviet Union) using a digital eyepiece attachment DCM130 (ScopeTek, China) and the ScopePhoto software (ScopeTek), which saved images in the JPEG format every 5 s. Automated image processing has been performed using an original software developed in the Laboratory of Developmental Biophysics, Bio logical Faculty, Moscow State University [10]. The coordinates of the growing tip distal end were deter mined from a succession of images by means of this software. The following active substances were used: octanol1 (SigmaAldrich, United States), carbenox DOKLADY BIOLOGICAL SCIENCES
Vol. 460
2015
olone disodium salt (SigmaAldrich), and gadolinium chloride (III) (SigmaAldrich). To study the role of gap junctions in cell communi cation in the course of growth pulsation, two blocking agents were used, octanol and carbenoxolone, the effi cacy of which has been demonstrated on numerous objects, including invertebrates [11]. The effects of both compounds were similar. When a colony was incubated in the presence of either octanol or car benoxolone, the tip growth decelerated. This effect was dependent on the concentration of the agents blocking gap junctions. At a concentration of 10 µM, both octanol and carbenoxolone reduced the growth rate by a factor of two, while at a concentration of 100 µM, they inhibited growth completely. The effects of both substances were not instantaneous: it took about 40 min to attain the maximum. After washing off
66
NIKISHIN et al.
Control, the stage of extension
Control, the stage of retraction
Gadolinium 50 μM
Carbenoxolon 100 μM
Fig. 2. The micrographs of G. loveni stolontip sections in control and on different stages of growth pulsation in experiments under the influence of agents blocking either (a) gap junctions (carbenoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)).
of the blocking agent, the growth rate was gradually restored (Fig. 1a). Despite the fact that, under the influence of agents blocking gap junctions, the tip growth is inhibited, the periodic extensions and retractions of the tips were still observed. Analysis of the growth curve characteristics showed that the period remained unchanged, but pulsation did not lead to any amount of growth (data not shown). As demonstrated by the timelapse video recording, there was no changes in epidermal cell orientation or tip sur face under the influence of the blocking agents, while changes in the gastroderm shape were still periodically observed. This evidence suggests that the gap junctions play a significant role in coordination of the epidermal cell movements. Histological analysis of the growing tips demonstrated that, under the influence of octanolol and carbenoxolone, the epidermal cells acquire elongated shape and inclined position with respect to the surface (Fig. 2). The angles of epidermal cell inclination at the stages of extension and retrac The inclination angle of epidermal cells, grad 60 The stage of extension 50 The stage of retraction * 40 30 20 10 0
Control Carbenoxolon Octanol
Gadolinium
Fig. 3. The epidermal cell inclination angles in G. loveni stolon tips on different stages of growth pulsation in con trol and in experiments under the influence of agents blocking either (a) gap junctions (carbenoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)). M± m; *p < 0.005 according to the Wilcoxon and Mann– Whitney tests, as compared to the values on the stages of cell extension and retraction in the control group.
tion were similar in the experimental group and corre sponded to the control values at the stage of retraction (Fig. 3). Thus, blocking of gap junctions prevented the epi dermal cell transition to the stage of extension; hence, these cells remained shrunk and obliquely oriented. According to the osmosis–contractile model of growth pulsation, the periodic alternation of the epi dermal cell extension and retraction is required for a amount of growth. In addition, transition to the stage of extension spreads throughout a growing tip in the form of a proximal–distal wave [6, 7]. Probably, a sig nal stimulating cell transition to the stage of extension is transmitted through the gap junctions within epider mis. Cell membrane depolarization serves, probably, as such a signal, which is confirmed by earlier data [2]. The role of mechanical factors in regulation of the osmosis–contractile mechanism of growth pulsation was studied in experiments with gadolinium ion (III), which inhibits specifically mechanosensitivity of the ion channels [12]. Gadolinium ceased completely the stolon tip growth at a concentration of 50 µM (Fig. 1b). As in the case of the gap junction blockage, the pulsation period remained almost unchanged, but the gadolin ium effect was mainly expressed in a smaller amount of growth. The gadolinium effect was instantaneous, but, after about 40 min, the growth rate restored gradually. This is most likely to be related to instability of gado linium ions in the presence of phosphates and carbon ates [12], because there was no growth recovery if gad olinium solution was periodically substituted for that freshly prepared. The influence of gadolinium on the rate of growth pulsation was reversible, and the effect disappeared immediately after washing off of the prep aration (Fig. 1b). Similar to the agents blocking gap junctions, gadolinium did not affect the gastrodermal pulsation component, but had an effect only on epi dermis. As determined by histological analysis, under the influence of gadolinium, the epidermal cell shape was typical of the stage of extension in most tips (Fig. 2). The inclination angles of epidermal cells did not differ sig DOKLADY BIOLOGICAL SCIENCES
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2015
ROLE OF GAP JUNCTIONS AND MECHANOSENSITIVE ION CHANNELS
nificantly at different stages of pulsation, and their val ues were intermediate between the control values at the stages of retraction and extension (Fig. 3).
67
REFERENCES
We are grateful to the staff of the Pertsov White Sea Biological Station, Moscow State University and per sonally to I.A. Kosevich for the help in organization of the work, as well as to L.V. Belousov for discussion of the results.
1. Labas, Yu.A., Belousov, L.V., and Kazakova, N.I., Tsi tologiya, 1992, vol. 34, no. 1, pp. 5–23. 2. Beloussov, L.V., Kazakova, N.I., Luchinskaia, N.N., et al., Int. J. Dev. Biol., 1997, vol. 41, pp. 793–799. 3. Belousov, L.V., Dokl. Akad. Nauk SSSR, 1961, vol. 136, no. 6, pp. 1490–1493. 4. Belousov, L.V., Ermakov, A.S., and Luchinskaya, N.N., Tsitologiya, 2000, vol. 42, no. 1, pp. 84–91. 5. Kosevich, I.A., Ontogenez, 2006, vol. 37, no. 2, pp. 115–129. 6. Zaraiskii, A.G., Belousov, L.V., Labas, Yu.A., et al., Ontogenez, 1984, vol. 15, no. 2, pp. 163–170. 7. Beloussov, L.V., Labas, J.A., Kazakova, N.I., et al., J. Exp. Zool., 1989, vol. 249, no. 3, pp. 258–270. 8. Alexopoulos, H., Boettger, A., and Fischer, S., Curr. Biol., 2004, vol. 14, no. 20, pp. 879–880. 9. Lee, J., Ishihara, A., Oxford, G., et al., Nature, 1999, vol. 400, no. 6742, pp. 382–386. 10. Troshina, T.G., Glagoleva, N.S., and Belousov, L.V., Ontogenez, 2011, vol. 42, no. 5, pp. 346–356. 11. Adler, E.L. and Woodruff, R.I., Arch. Insect. Biochem. Physiol., 2000, vol. 43, no. 1, pp. 22–32. 12. Adding, L.C., Bannenberg, G.L., and Gustafsson, L.E., Cardiovasc. Drug. Rev., 2001, vol. 19, no. 1, pp. 41–56. 13. Labas, Yu.A., Zinchenko, V.P., Belousov, L.V., et al., Zh. Obshch. Biol., 1989, vol. 50, no. 4, pp. 504–515.
This study was supported by the Russian Founda tion for Basic Research (project no. 140400337).
Translated by A. Nikolaeva
Thus, blockage of the mechanosensitive ion chan nels impairs the ability of tip epidermal cells to enter the stage of retraction. Fusion of cell vesicles, as well as active cell movements, which take place at this stage, are known to be calciumdependent processes [13]. The mechanosensitive calcium channels repressible by gadolinium ions are most likely involved in the induc tion of the retraction stage of growth pulsation. Thus, we have obtained evidence suggesting that gap junctions and mechanosensitive ion channels play an important role in growth pulsation of hydroid pol yps; the functional activity of gap junctions is more important at the stage of extension; mechanosensitive ion channels, at the stage of retraction. ACKNOWLEDGMENTS
DOKLADY BIOLOGICAL SCIENCES
Vol. 460
2015
CELL BIOLOGY
Role of Gap Junctions and Mechanosensitive Ion Channels in the Mechanisms of Growth Pulsations of Gonothyraea loveni D. A. Nikishina, b, S. V. Kremnyova, and N. S. Glagolevaa Presented by Academician S.A. Lukyanov August 28, 2014 Received August 28, 2014
DOI: 10.1134/S0012496615010184
dermal cells, gastrodermal cells are always extremely vacuolated, and their movements are not accompa nied by changes in volume. The gastrodermal compo nent of growth pulsation includes changes in the shape of the gastrodermal tube: the tube narrowing and elon gation (probably, through contraction of the annular muscle processes of the epithelial–muscular gastro dermal cells) alternate with the tube thickening and shortening [5]. Thus, growth pulsation is a result of coordinated movements of epidermal and gastroder mal cells: the gastroderm is involved in pushing the apex and stretching of young perisarc; the epidermal cell movements ensure fixation of a amount of growth. What remains unclear is how cell movements are coordinated during pulsating growth. Changes in cell orientation have been noticed to spread wavelike in the proximal–distal direction. Only at the stage of short ening do all cells begin to move almost synchronously [6]. In epithelia, cell communications can take place via the gap junctions by means of depolarization or signaling molecules. The gap junction proteins, innex ines, have been described in invertebrates, including Coelenterata [8]. Cell movements during growth pul sation are most likely coordinated via the gap junc tions, which explains the proximal–distal waves of cell movements. On the other hand, during the retraction stage, triggering of cell movements occurs probably due to activation of the mechanosensitive ion channels [1], as it happens in the case of directed movements of keratinocytes [9]. Here, we studied the mechanisms underlying coor dination of cell movements during growth pulsation of hydroid polyps and; the stolon tips served as the sim plest system, because it is not exposed to morphogen esis and is methodically convenient. The study has been conducted on the Pertsov White Sea Biological Station, Moscow State University. Col onies of Gonothyraea loveni (Allman, 1859) were col lected on the Eremeevsky Rapids (66°33′06.8′′ N, 33°06′57.2′′ E). The shoot fragments placed on glass slides were planted in an aerated aquarium and culti
Growth and morphogenesis of all rudiments of colonial hydroid polyps occurs due to pulsation of a specialized apical portion of the colony body, the growing tips. Growth pulsation is a result of recurrent proximal–distal waves of contractions and relaxations of epi and gastrodermal cells. There is no prolifera tion within the growing tips and growth is exclusively due to cell movements [1]. The shape of a developing rudiment is directly dependent on the growth pulsa tion parameters in the course of natural or experimen tal apical growth [2]. The mechanisms underlying growth pulsation of hydroid polyps are of interest because hydroid polyps represent a simple and con trollable model of the epithelial morphogenesis, which is widely involved in organogenesis of many animals, including mammals. The cellular mechanisms of growth pulsation in hydroid polyps are well described in studies by Belousov [1–3] and Kosevich [5]. While growing, the hydroid tips have successive rhythmic cell movements leading to a gradual slight amount of growth after each cycle. This phenomenon is accompanied by periodic changes in the volume and orientation of epidermal cells by means of the osmosis–contractile mechanism. An increase in epidermal cell volume occurs at the stage of extension because of accumulation of volumi nous vacuoles; after vacuole fusion, they are poured out into the environment to reduce the cell volume at the stage of retraction [6, 7]. At the same time, the proximal–distal shifts of cell apical surfaces take place, which makes it possible to start the next cycle of cell movements from a new point. As demonstrated by indi rect methods, the retraction phase is accompanied by cell membrane depolarization, as well as by an increase in the cytoplasmic calcium concentration [2, 7]. Unlike epi
a
Moscow State University, Moscow, 119234 Russia; email; [email protected] b Kol’tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 117808 Russia 64
ROLE OF GAP JUNCTIONS AND MECHANOSENSITIVE ION CHANNELS
65
(a)
Amount of growth, μm 200 Control Carbenoxolon 100 μM 150
Washing
100
50
0
20
40
60
80
100
120 Time, min
80
100
120 Time, min
(b)
Amount of growth, μm 200 Control Gadolinium 50 μM 150
Washing
100
50
0
20
40
60
Fig. 1. The growth pulsation curves of G. loveni stolon tips under the influence of the agents blocking either (a) gap junctions (car benoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)).
vated at room temperature (20–22°С) and daily fed with Artemia nauplii. The young colonies grown for three days consisted of the maternal shoot, stolon, and one or two new shoots. Wellgrowing stolon tips with out anomalies were used in the experiments. The sto lon tip growth was examined using an MBI1 (LOMO, Soviet Union) using a digital eyepiece attachment DCM130 (ScopeTek, China) and the ScopePhoto software (ScopeTek), which saved images in the JPEG format every 5 s. Automated image processing has been performed using an original software developed in the Laboratory of Developmental Biophysics, Bio logical Faculty, Moscow State University [10]. The coordinates of the growing tip distal end were deter mined from a succession of images by means of this software. The following active substances were used: octanol1 (SigmaAldrich, United States), carbenox DOKLADY BIOLOGICAL SCIENCES
Vol. 460
2015
olone disodium salt (SigmaAldrich), and gadolinium chloride (III) (SigmaAldrich). To study the role of gap junctions in cell communi cation in the course of growth pulsation, two blocking agents were used, octanol and carbenoxolone, the effi cacy of which has been demonstrated on numerous objects, including invertebrates [11]. The effects of both compounds were similar. When a colony was incubated in the presence of either octanol or car benoxolone, the tip growth decelerated. This effect was dependent on the concentration of the agents blocking gap junctions. At a concentration of 10 µM, both octanol and carbenoxolone reduced the growth rate by a factor of two, while at a concentration of 100 µM, they inhibited growth completely. The effects of both substances were not instantaneous: it took about 40 min to attain the maximum. After washing off
66
NIKISHIN et al.
Control, the stage of extension
Control, the stage of retraction
Gadolinium 50 μM
Carbenoxolon 100 μM
Fig. 2. The micrographs of G. loveni stolontip sections in control and on different stages of growth pulsation in experiments under the influence of agents blocking either (a) gap junctions (carbenoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)).
of the blocking agent, the growth rate was gradually restored (Fig. 1a). Despite the fact that, under the influence of agents blocking gap junctions, the tip growth is inhibited, the periodic extensions and retractions of the tips were still observed. Analysis of the growth curve characteristics showed that the period remained unchanged, but pulsation did not lead to any amount of growth (data not shown). As demonstrated by the timelapse video recording, there was no changes in epidermal cell orientation or tip sur face under the influence of the blocking agents, while changes in the gastroderm shape were still periodically observed. This evidence suggests that the gap junctions play a significant role in coordination of the epidermal cell movements. Histological analysis of the growing tips demonstrated that, under the influence of octanolol and carbenoxolone, the epidermal cells acquire elongated shape and inclined position with respect to the surface (Fig. 2). The angles of epidermal cell inclination at the stages of extension and retrac The inclination angle of epidermal cells, grad 60 The stage of extension 50 The stage of retraction * 40 30 20 10 0
Control Carbenoxolon Octanol
Gadolinium
Fig. 3. The epidermal cell inclination angles in G. loveni stolon tips on different stages of growth pulsation in con trol and in experiments under the influence of agents blocking either (a) gap junctions (carbenoxolon) or (b) mechanosensitive ion channels (gadolinium ion (III)). M± m; *p < 0.005 according to the Wilcoxon and Mann– Whitney tests, as compared to the values on the stages of cell extension and retraction in the control group.
tion were similar in the experimental group and corre sponded to the control values at the stage of retraction (Fig. 3). Thus, blocking of gap junctions prevented the epi dermal cell transition to the stage of extension; hence, these cells remained shrunk and obliquely oriented. According to the osmosis–contractile model of growth pulsation, the periodic alternation of the epi dermal cell extension and retraction is required for a amount of growth. In addition, transition to the stage of extension spreads throughout a growing tip in the form of a proximal–distal wave [6, 7]. Probably, a sig nal stimulating cell transition to the stage of extension is transmitted through the gap junctions within epider mis. Cell membrane depolarization serves, probably, as such a signal, which is confirmed by earlier data [2]. The role of mechanical factors in regulation of the osmosis–contractile mechanism of growth pulsation was studied in experiments with gadolinium ion (III), which inhibits specifically mechanosensitivity of the ion channels [12]. Gadolinium ceased completely the stolon tip growth at a concentration of 50 µM (Fig. 1b). As in the case of the gap junction blockage, the pulsation period remained almost unchanged, but the gadolin ium effect was mainly expressed in a smaller amount of growth. The gadolinium effect was instantaneous, but, after about 40 min, the growth rate restored gradually. This is most likely to be related to instability of gado linium ions in the presence of phosphates and carbon ates [12], because there was no growth recovery if gad olinium solution was periodically substituted for that freshly prepared. The influence of gadolinium on the rate of growth pulsation was reversible, and the effect disappeared immediately after washing off of the prep aration (Fig. 1b). Similar to the agents blocking gap junctions, gadolinium did not affect the gastrodermal pulsation component, but had an effect only on epi dermis. As determined by histological analysis, under the influence of gadolinium, the epidermal cell shape was typical of the stage of extension in most tips (Fig. 2). The inclination angles of epidermal cells did not differ sig DOKLADY BIOLOGICAL SCIENCES
Vol. 460
2015
ROLE OF GAP JUNCTIONS AND MECHANOSENSITIVE ION CHANNELS
nificantly at different stages of pulsation, and their val ues were intermediate between the control values at the stages of retraction and extension (Fig. 3).
67
REFERENCES
We are grateful to the staff of the Pertsov White Sea Biological Station, Moscow State University and per sonally to I.A. Kosevich for the help in organization of the work, as well as to L.V. Belousov for discussion of the results.
1. Labas, Yu.A., Belousov, L.V., and Kazakova, N.I., Tsi tologiya, 1992, vol. 34, no. 1, pp. 5–23. 2. Beloussov, L.V., Kazakova, N.I., Luchinskaia, N.N., et al., Int. J. Dev. Biol., 1997, vol. 41, pp. 793–799. 3. Belousov, L.V., Dokl. Akad. Nauk SSSR, 1961, vol. 136, no. 6, pp. 1490–1493. 4. Belousov, L.V., Ermakov, A.S., and Luchinskaya, N.N., Tsitologiya, 2000, vol. 42, no. 1, pp. 84–91. 5. Kosevich, I.A., Ontogenez, 2006, vol. 37, no. 2, pp. 115–129. 6. Zaraiskii, A.G., Belousov, L.V., Labas, Yu.A., et al., Ontogenez, 1984, vol. 15, no. 2, pp. 163–170. 7. Beloussov, L.V., Labas, J.A., Kazakova, N.I., et al., J. Exp. Zool., 1989, vol. 249, no. 3, pp. 258–270. 8. Alexopoulos, H., Boettger, A., and Fischer, S., Curr. Biol., 2004, vol. 14, no. 20, pp. 879–880. 9. Lee, J., Ishihara, A., Oxford, G., et al., Nature, 1999, vol. 400, no. 6742, pp. 382–386. 10. Troshina, T.G., Glagoleva, N.S., and Belousov, L.V., Ontogenez, 2011, vol. 42, no. 5, pp. 346–356. 11. Adler, E.L. and Woodruff, R.I., Arch. Insect. Biochem. Physiol., 2000, vol. 43, no. 1, pp. 22–32. 12. Adding, L.C., Bannenberg, G.L., and Gustafsson, L.E., Cardiovasc. Drug. Rev., 2001, vol. 19, no. 1, pp. 41–56. 13. Labas, Yu.A., Zinchenko, V.P., Belousov, L.V., et al., Zh. Obshch. Biol., 1989, vol. 50, no. 4, pp. 504–515.
This study was supported by the Russian Founda tion for Basic Research (project no. 140400337).
Translated by A. Nikolaeva
Thus, blockage of the mechanosensitive ion chan nels impairs the ability of tip epidermal cells to enter the stage of retraction. Fusion of cell vesicles, as well as active cell movements, which take place at this stage, are known to be calciumdependent processes [13]. The mechanosensitive calcium channels repressible by gadolinium ions are most likely involved in the induc tion of the retraction stage of growth pulsation. Thus, we have obtained evidence suggesting that gap junctions and mechanosensitive ion channels play an important role in growth pulsation of hydroid pol yps; the functional activity of gap junctions is more important at the stage of extension; mechanosensitive ion channels, at the stage of retraction. ACKNOWLEDGMENTS
DOKLADY BIOLOGICAL SCIENCES
Vol. 460
2015
