• Applied Microscopy
• /
• v.20 no.1
• /
• pp.65-76
• /
• 1990

The effect of calcium-free reperfusion for 5, 10, and 15 minutes, respectively, followed by continuous reperfusion with normal Tyrode solution containing 1.0mM calcium chloride, after global ischemia in the isolated perfused guinea pig heart by Langendorff techniques was examined with transmission electron microscope. Compared to the nomal Tyrode solution-perfused control hearts, the 5 minute calcium-free-reperfused hearts showed loss or thickening of Z lines, focal sarcolemmal disruption, mitochondrial swelling, clumping of chroma-tin, intracellular fluid accumulation, and some separation of cell junctions, especially the fasciae adherentes. These changes became more severe in the hearts of 10 minute calcium-free reperfusion. Subsarcolemmal larger bleb and near complete separation of cell junctions were noticed. In the 15 minute calcium-free-reperfused hearts, irreversible ultrastructural changes including contraction bands, biazrre mitochondria, and sarcolemmal destruction were widely distributed. The severity of myocardial changes were in accordance with the duration of calcium-free reperfusion. These changes indicate that calcium-free reperfusion regardless of its duration could not salvage the post-ischemic myocardium probably due to development of calcium paradox.

• Proceedings of the Korean Society of Toxicology Conference
• /
• 2005.05a
• /
• pp.146-146
• /
• 2005

• Proceedings of the Korea Environmental Mutagen Society Conference
• /
• 2004.05a
• /
• pp.89-89
• /
• 2004

• The Korean Journal of Physiology and Pharmacology
• /
• v.21 no.2
• /
• pp.241-249
• /
• 2017

Plasma membrane hyperpolarization associated with activation of $Ca^{2+}$-activated $K^+$ channels plays an important role in sperm capacitation during fertilization. Although Slo3 (slowpoke homologue 3), together with the auxiliary ${\gamma}^2$-subunit, LRRC52 (leucine-rich-repeat-containing 52), is known to mediate the pH-sensitive, sperm-specific $K^+$ current KSper in mice, the molecular identity of this channel in human sperm remains controversial. In this study, we tested the classical $BK_{Ca}$ activators, NS1619 and LDD175, on human Slo3, heterologously expressed in HEK293 cells together with its functional interacting ${\gamma}^2$ subunit, hLRRC52. As previously reported, Slo3 $K^+$ current was unaffected by iberiotoxin or 4-aminopyridine, but was inhibited by ~50% by 20 mM TEA. Extracellular alkalinization potentiated hSlo3 $K^+$ current, and internal alkalinization and $Ca^{2+}$ elevation induced a leftward shift its activation voltage. NS1619, which acts intracellularly to modulate hSlo1 gating, attenuated hSlo3 $K^+$ currents, whereas LDD175 increased this current and induced membrane potential hyperpolarization. LDD175-induced potentiation was not associated with a change in the half-activation voltage at different intracellular pHs (pH 7.3 and pH 8.0) in the absence of intracellular $Ca^{2+}$. In contrast, elevation of intracellular $Ca^{2+}$ dramatically enhanced the LDD175-induced leftward shift in the half-activation potential of hSlo3. Therefore, the mechanism of action does not involve pH-dependent modulation of hSlo3 gating; instead, LDD175 may modulate $Ca^{2+}$-dependent activation of hSlo3. Thus, LDD175 potentially activates native KSper and may induce membrane hyperpolarization-associated hyperactivation in human sperm.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.7
• /
• pp.949-956
• /
• 2002

There are several physiological and pharmacological evidences indicating that opening of voltage dependent $Ca^{2+}$ channels play a critical role in induction of acrosome reaction in mammalian sperm. We determined the intracellular free $Ca^{2+}$ concentration in ejaculated goat sperm using a fluorescent, $Ca^{2+}$-specific probe, Fura2/AM, after the suspension of sperm in KRB medium, capable of sustaining capacitation and the acrosome reaction. We used nifedipine, D-600 and diltiazem, the $Ca^{2+}$ channel antagonists belonging to the classes of dihydropyridines, phenylalkylamines and benzothiazepines, to investigate the possibility that L-type voltage gated $Ca^{2+}$ channels play a role in the progesterone-stimulated exocytotic response. Progesterone promoted a rise in intracellular $Ca^{2+}$ in goat sperm and addition of nifedipine (100 nM) just prior to progesterone induction, significantly inhibited both intracellular $Ca^{2+}$ rise and exocytosis suggesting that $Ca^{2+}$ channels are involved in the process. However, the intracellular $Ca^{2+}$ increase during the process of capacitation was not affected with the addition of nifedipine suggesting a role of focal channel for $Ca^{2+}$ during capacitation. Studies using monensin and nigericin, two monovalent cation ionophores showed that an influx of $Na^+$ also may play a role in the opening of $Ca^{2+}$ channels. These results strongly suggests that the entry of $Ca^{2+}$ channels with characteristics similar to those of L-type, voltage-sensitive $Ca^{2+}$ channels found in cardiac and skeletal muscle, is a crucial step in the sequence of events leading to progesterone induced acrosome reaction in goat sperm.

• Journal of Chest Surgery
• /
• v.19 no.2
• /
• pp.197-208
• /
• 1986

Propranolol is one of clinically useful antiarrhythmic agents and electrophysiologically classified as group II. And the negative inotropic effect which is not related to adrenolytic effect has been demonstrated with high concentration of propranolol. On the other hand, it has been well known that the calcium plays a central role in excitation-contraction coupling process of myocardium and also in electrophysiological changes of cell membrane. Author studies the effect of propranolol on calcium uptake and release in sarcoplasmic reticulum and mitochondria prepared from porcine myocardium to investigate the mechanism of action of propranolol on myocardium. The results are summarized as follow: 1] The maximum Ca++-uptake of sarcoplasmic reticulum is inhibited by propranolol in a dose dependent manner. 2] The release of calcium from sarcoplasmic reticulum is not affected by propranolol but with higher than 1x10-3 M of propranolol, rate of calcium release from sarcoplasmic reticulum is decreased. 3] Propranolol inhibits the maximum uptake and uptake rate of calcium in mitochondria non-competitively. [Ki = 6.21 x 10-4 M] 4] The rate of Na+ induced calcium release from mitochondrion shows a function of [Na+]2 and is inhibited by propranolol with the concentration significantly lower than that affect the calcium uptake in sarcoplasmic reticulum and in mitochondria [Ki = 2.91 x 10-5 M]. These results suggest that propranolol affects the intracellular calcium homeostasis which may considered to be one of the mechanism of action of propranolol on myocardium.

• Journal of Plant Biology
• /
• v.39 no.2
• /
• pp.113-121
• /
• 1996

The role of Ca2+ on benzyladenine (BA)-induced senescence retardation in mature wheat (Triticum aestivum L.) primary leaves was investigated. When an extracellular calcium chelator, ethylene glycol-bis-($\beta$-aminoethylether)-N, N'-tetraacetic acid (EGTA) together with BA, was applied to senescing leaves for 4 days of dark incubation, the content of chlorophyll and soluble protein decreased rapidly. And, the content of malondialdehyde (MDA), known to be a degradation product of membrane lipids, increased compared with the BA alone control. The BA-EGTA combination also caused the stimulation of protease and RNase activity and a rapid loss of catalase activity owing to the decling of BA effects. In the case of treatment with only intracellular calcium antagonist 3, 4, 5-trimethoxybenzoic acid 8-(diethylamino) octyl ester (TMB-8) without the BA addition, the chlorophyll content at day 4 after dark incubation decreased in paralled with the increasing concentration of the antagonist. In addition, the chlorophyll content at 10-5 M calcium ionophore A23187 treatment in the absence of BA was similar to that of the BA alone treatment. These results suggest that calcium may mediate the retardation effect of BA on leaf senescence by acting as a second messenger and that the calcium input from cell organelles, as well as the calcium inflow from intercellular spaces and cell walls, may be involved in modulating cytosolic calcium levels related to BA action.

• ALGAE
• /
• v.33 no.2
• /
• pp.181-189
• /
• 2018

Emiliania huxleyi (a haptophyte) is the most abundant coccolithophore species that produces delicate calcite scales called coccoliths. In this study, we identified several candidate genes associated with coccolith production by comparing the transcriptomes of the calcifying (CCMP 371) and non-calcifying (CCMP 2090) strains of E. huxleyi. Among the candidates, genes highly expressed in CCMP 371 were identified. To confirm whether these genes are associated with calcification, we modulated coccolith production in CCMP 371 by culturing it at different calcium concentrations. At an ambient (10 mM) concentration of calcium in the growth medium, CCMP 371 sustained its calcifying ability. However, at a low (0.1 mM) concentration or absence of calcium, there was no calcite formation, demonstrating that calcium-limiting conditions negatively affect calcification. We also evaluated the expression patterns of the putative genes in cells grown at different calcium concentrations by quantitative reverse transcription polymerase chain reaction. In addition, we showed that the growth rate of cells cultured under calcium-limiting conditions does not differ from that under ambient conditions. Further studies are required to investigate the roles of the putative calcification-associated genes at the molecular level.

• The Korean Journal of Physiology and Pharmacology
• /
• v.23 no.4
• /
• pp.237-249
• /
• 2019

Confirming the direct link between neural circuit activity and animal behavior has been a principal aim of neuroscience. The genetically encoded calcium indicator (GECI), which binds to calcium ions and emits fluorescence visualizing intracellular calcium concentration, enables detection of in vivo neuronal firing activity. Various GECIs have been developed and can be chosen for diverse purposes. These GECI-based signals can be acquired by several tools including two-photon microscopy and microendoscopy for precise or wide imaging at cellular to synaptic levels. In addition, the images from GECI signals can be analyzed with open source codes including constrained non-negative matrix factorization for endoscopy data (CNMF_E) and miniscope 1-photon-based calcium imaging signal extraction pipeline (MIN1PIPE), and considering parameters of the imaged brain regions (e.g., diameter or shape of soma or the resolution of recorded images), the real-time activity of each cell can be acquired and linked with animal behaviors. As a result, GECI signal analysis can be a powerful tool for revealing the functions of neuronal circuits related to specific behaviors.

• Journal of Ginseng Research
• /
• v.20 no.2
• /
• pp.159-167
• /
• 1996

To study the effects of ginseng saponin components on the signal transduction in the ac tivation of murine macrophages, phagocytosis and Intracellular calcium concentration of peritoneal exuded mouse macrophages were examined. The phagocytosis was increased significantly after treatment with total saponin, diol-saponin, $Rg_1$ and $Rg_2$, but triol-saponin was unable to increase phagocytosis. The phagocytosis were increased when H7, a PKC inhibitor, was pretreated and increased significantly by saponin fractions except total saponin. Pertussis toxin, which inactivates G-protein, decreased the phagocytosis. But the phagocytosis was restored to the control level by saponin fractions and the phagocytosis was increased significantly by $Rg_2$ and $Rg_2$. The triol saponin increased phagocytosis approximately by 2-fold as compared with the TMB-8 treated group. Peritoneal exuded macrophages displayed a prominent rise in cytosolic calcium following treatment with triol-saponin, $Rg_1$, $Rg_2$ and $Rg_2$. Incubation of macrophages with PT resulted in an inhibition of cytosolic calcium mobilization, but increased cytosolic calcium mobilization with saponin fraction.