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1.
Activation of salivary secretion: coupling of cell volume and [Ca2+]i in single cells 总被引：7，自引：0，他引：7
High-resolution differential interference contrast microscopy and digital imaging of the fluorescent calcium indicator dye fura-2 were performed simultaneously in single rat salivary gland acinar cells to examine the effects of muscarinic stimulation on cell volume and cytoplasmic calcium concentration ([Ca2+]i). Agonist stimulation of fluid secretion is initially associated with a rapid tenfold increase in [Ca2+]i as well as a substantial cell shrinkage. Subsequent changes of cell volume in the continued presence of agonist are tightly coupled to dynamic levels of [Ca2+]i, even during [Ca2+]i oscillations. Experiments with Ca2+ chelators and ionophores showed that physiological elevations of [Ca2+]i are necessary and sufficient to cause changes in cell volume. The relation between [Ca2+]i and cell volume suggests that the latter reflects the secretory state of the acinar cell. Agonist-induced changes in [Ca2+]i, by modulating specific ion permeabilities, result in solute movement into or out of the cell. The resultant cell volume changes may be important in modulating salivary secretion. 相似文献
2.
Atrionatriuretic peptide transforms cardiac sodium channels into calcium-conducting channels 总被引：3，自引：0，他引：3
The atrionatriuretic peptide (ANP) is released from atrial cells in response to increased extracellular fluid volume and reduces sodium absorption by the kidney, thus reducing the blood volume. In this report, ANP suppressed the calcium and sodium currents in rat and guinea pig ventricular myocytes. The suppression of sodium current was caused by enhanced permeability of the sodium channel to calcium without significant changes in the kinetics or the tetrodotoxin sensitivity of the channel. Thus, ANP may regulate the sodium channel by altering its cationic selectivity site to calcium, thereby repressing the sodium current. The suppression of sodium and calcium channels and the resultant depressed excitability of the atrial cells may help to regulate ANP secretion. 相似文献
3.
INOUE T 《Science (New York, N.Y.)》1963,142(3597):1299-1300
The nasal salt-secreting gland of the domestic duck can produce a fluid with a sodium chloride concentration about three times that in blood plasma. To study the cellular mechanism responsible for the formation of the highly concentrated fluid, the gland was poisoned by retrograde injection of mercuric chloride into the lumen, decreasing the salt concentration to that in plasma while the volume of secretion was unchanged. Carbonic anhydrase inhibitor (acetazoleamide) caused a moderate decrease in salt concentrations, again with maintenance of volume of secretion. The results suggest that concentration and volume of the secreted fluid depend on two different cellular mechanisms. 相似文献
4.
Futatsugi A Nakamura T Yamada MK Ebisui E Nakamura K Uchida K Kitaguchi T Takahashi-Iwanaga H Noda T Aruga J Mikoshiba K 《Science (New York, N.Y.)》2005,309(5744):2232-2234
Type 2 and type 3 inositol 1,4,5-trisphosphate receptors (IP3R2 and IP3R3) are intracellular calcium-release channels whose physiological roles are unknown. We show exocrine dysfunction in IP3R2 and IP3R3 double knock-out mice, which caused difficulties in nutrient digestion. Severely impaired calcium signaling in acinar cells of the salivary glands and the pancreas in the double mutants ascribed the secretion deficits to a lack of intracellular calcium release. Despite a normal caloric intake, the double mutants were hypoglycemic and lean. These results reveal IP3R2 and IP3R3 as key molecules in exocrine physiology underlying energy metabolism and animal growth. 相似文献
5.
在研究中国水牛鼻唇腺显微与亚微结构的基础上,对水牛鼻唇腺的组织化学(核酸、多糖、糖蛋白、脂类,碱性磷酸酶和酸性磷酸酶等)进行测定。显微镜观察表明,鼻唇腺腺泡细胞胞质与导管管腔内的分泌物均含较多的 PAS 阳性颗粒。用不同 pH 的 AB 染色加以鉴别,证实这些 PAS阳性颗粒属于涎粘液,是分泌物的重要成分。鼻唇腺是一种由纯浆液性腺泡构成的唾液腺,其分泌物通过导符系统运送到鼻唇镜表面,水牛不断用舌舔其表面,从而咽入腺体分泌物。 相似文献
6.
《Science (New York, N.Y.)》1989,245(4916):343
In the report "Activation of salivary secretion: Coupling of cell volume and [Ca(2+)](i) in single cells" by J. K. Foskett and J. E. Melvin (30 June, p. 1582), figures 1 and 2 were inadvertently interchanged. The correct figures are printed below. [See Figures in source pdf.]. 相似文献
7.
The role of sodium-calcium exchange at the sarcolemma in the release of calcium from cardiac sarcoplasmic reticulum was investigated in voltage-clamped, isolated cardiac myocytes. In the absence of calcium entry through voltage-dependent calcium channels, membrane depolarization elicited release of calcium from ryanodine-sensitive internal stores. This process was dependent on sodium entry through tetrodotoxin-sensitive sodium channels. Calcium release under these conditions was also dependent on extracellular calcium concentration, suggesting a calcium-induced trigger release mechanism that involves calcium entry into the cell by sodium-calcium exchange. This sodium current-induced calcium release mechanism may explain, in part, the positive inotropic effects of cardiac glycosides and the negative inotropic effects of a variety of antiarrhythmic drugs that interact with cardiac sodium channels. In response to a transient rise of intracellular sodium, sodium-calcium exchange may promote calcium entry into cardiac cells and trigger sarcoplasmic calcium release during physiologic action potentials. 相似文献
8.
Regulation of chloride channels by protein kinase C in normal and cystic fibrosis airway epithelia 总被引：21，自引：0，他引：21
M Li J D McCann M P Anderson J P Clancy C M Liedtke A C Nairn P Greengard M J Welsch 《Science (New York, N.Y.)》1989,244(4910):1353-1356
Apical membrane chloride channels control chloride secretion by airway epithelial cells. Defective regulation of these channels is a prominent characteristic of cystic fibrosis. In normal intact cells, activation of protein kinase C (PKC) by phorbol ester either stimulated or inhibited chloride secretion, depending on the physiological status of the cell. In cell-free membrane patches, PKC also had a dual effect: at a high calcium concentration, PKC inactivated chloride channels; at a low calcium concentration, PKC activated chloride channels. In cystic fibrosis cells, PKC-dependent channel inactivation was normal, but activation was defective. Thus it appears that PKC phosphorylates and regulates two different sites on the channel or on an associated membrane protein, one of which is defective in cystic fibrosis. 相似文献
9.
Generation of calcium oscillations in fibroblasts by positive feedback between calcium and IP3 总被引：22，自引：0，他引：22
A wide variety of nonexcitable cells generate repetitive transient increases in cytosolic calcium ion concentration ([Ca2+]i) when stimulated with agonists that engage the phosphoinositide signalling pathway. Current theories regarding the mechanisms of oscillation disagree on whether Ca2+ inhibits or stimulates its own release from internal stores and whether inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DG) also undergo oscillations linked to the Ca2+ spikes. In this study, Ca2+ was found to stimulate its own release in REF52 fibroblasts primed by mitogens plus depolarization. However, unlike Ca2+ release in muscle and nerve cells, this amplification was insensitive to caffeine or ryanodine and required hormone receptor occupancy and functional IP3 receptors. Oscillations in [Ca2+]i were accompanied by oscillations in IP3 concentration but did not require functional protein kinase C. Therefore, the dominant feedback mechanism in this cell type appears to be Ca2+ stimulation of phospholipase C once this enzyme has been activated by hormone receptors. 相似文献
10.
Direct demonstration of macula densa-mediated renin secretion 总被引：10，自引：0，他引：10
An in vitro method has been used to examine whether secretion of renin from the juxtaglomerular apparatus is affected by changes in the sodium chloride concentration of the tubular fluid at the macula densa. Single juxtaglomerular apparatuses were microdissected from rabbits and the tubule segment containing the macula densa was perfused, while simultaneously the entire juxtaglomerular apparatus was superfused, and the fluid was collected for renin measurement. In this preparation, in which influences from renal nerves and local hemodynamic effects are eliminated, a decrease in the tubular sodium chloride concentration at the macula densa results in a prompt stimulation of the renin release rate. 相似文献
11.
Allen GJ Chu SP Schumacher K Shimazaki CT Vafeados D Kemper A Hawke SD Tallman G Tsien RY Harper JF Chory J Schroeder JI 《Science (New York, N.Y.)》2000,289(5488):2338-2342
Cytosolic calcium oscillations control signaling in animal cells, whereas in plants their importance remains largely unknown. In wild-type Arabidopsis guard cells abscisic acid, oxidative stress, cold, and external calcium elicited cytosolic calcium oscillations of differing amplitudes and frequencies and induced stomatal closure. In guard cells of the V-ATPase mutant det3, external calcium and oxidative stress elicited prolonged calcium increases, which did not oscillate, and stomatal closure was abolished. Conversely, cold and abscisic acid elicited calcium oscillations in det3, and stomatal closure occurred normally. Moreover, in det3 guard cells, experimentally imposing external calcium-induced oscillations rescued stomatal closure. These data provide genetic evidence that stimulus-specific calcium oscillations are necessary for stomatal closure. 相似文献
12.
Endothelin stimulation of cytosolic calcium and gonadotropin secretion in anterior pituitary cells 总被引：11，自引：0，他引：11
S S Stojilkovi? F Merelli T Iida L Z Krsmanovi? K J Catt 《Science (New York, N.Y.)》1990,248(4963):1663-1666
The presence of endothelin, a vasoconstrictor peptide, in the hypothalamus and posterior pituitary suggests that it also regulates neural and other nonvascular target cells. In pituitary gonadotrophs, low doses of endothelin evoked oscillations in the intracellular calcium concentration, and high doses induced a biphasic calcium response. Mobilization of intracellular calcium predominated during the spike phase of the calcium response to endothelin, whereas calcium entry through dihydropyridine-sensitive channels contributed to both the spike and plateau phases of the calcium response. Endothelin was a potent as hypothalamic gonadotropin-releasing hormone (GnRH) in stimulation of gonadotropin release in perifused pituitary cells. Endothelin bound specifically to pituitary cells with a dissociation constant of 70 picomolar, and induced rapid formation of inositol trisphosphate and diacyglycerol. Although intracellular calcium concentration and gonadotropin secretory responses to endothelin were independent to the GnRH receptor, endothelin and GnRH appeared to have a common signal transduction mechanism. These observations suggest that endothelin can act as a neuropeptide to regulate anterior pituitary function. 相似文献
13.
Insect salivary glands: stimulation of fluid secretion by 5-hydroxytryptamine and adenosine-3',5'-monophosphate 总被引：4，自引：0，他引：4
Low concentrations (10(-9)M) of 5-hydroxytryptamine increase the rate of fluid secretion by isolated salivary glands of adult Calliphora. 5-Hydroxytry ptamine is present in Calliphora brain. Adenosine-3',5'-monophosphate (cyclic AMP) also stimulates fluid secretion and may be involved in the mode of action of 5-hydroxytryptamine. 相似文献
14.
本文报道了引入甘肃省武威地区的豁眼鹅及皖西白鹅的某些生理生化常值和性激素水平。测定项目有红细胞数、血红蛋白、白细胞总数、白细胞分类计数、血清总蛋白、血糖、血脂、血液钙、磷、镁、钾、钠、氯离子含量以及雌二醇和睾酮水平。结果表明:具较高产蛋量的豁眼鹅雌鹅其雌二醇水平显著高于皖西白鹅雌鹅,前者血液总蛋白、血糖、血脂、血钙、血磷含量显著或极显著高于后者。说明这几项常值与产蛋性状有关。睾酮含量对红细胞数目起一定作用。文中还讨论了性激素水平对公鹅配种能力的影响。 相似文献
15.
张兆旺 《甘肃农业大学学报》1993,28(4):384-387
测定了60只引入甘肃省兰州地区乌骨鸡血液中红细胞数,血红蛋白,红细胞压积,白细胞总数,白细胞分类计数,血糖,血清胆固醇,钠、钾、氯、无机磷和钙水平等生理生化常值。其结果均在正常范围内,还讨论了鸡冠类型、引种地和性别对上述测定项目的影响。 相似文献
16.
Tang RH Han S Zheng H Cook CW Choi CS Woerner TE Jackson RB Pei ZM 《Science (New York, N.Y.)》2007,315(5817):1423-1426
Various signaling pathways rely on changes in cytosolic calcium ion concentration ([Ca2+]i). In plants, resting [Ca2+]i oscillates diurnally. We show that in Arabidopsis thaliana, [Ca2+]i oscillations are synchronized to extracellular Ca2+ concentration ([Ca2+]o) oscillations largely through the Ca2+-sensing receptor CAS. CAS regulates concentrations of inositol 1,4,5-trisphosphate (IP3), which in turn directs release of Ca2+ from internal stores. The oscillating amplitudes of [Ca2+]o and [Ca2+]i are controlled by soil Ca2+ concentrations and transpiration rates. The phase and period of oscillations are likely determined by stomatal conductance. Thus, the internal concentration of Ca2+ in plant cells is constantly being actively revised. 相似文献
17.
Aberrant centrosome duplication is observed in many tumor cells and may contribute to genomic instability through the formation of multipolar mitotic spindles. Cyclin-dependent kinase 2 (Cdk2) is required for multiple rounds of centrosome duplication in Xenopus egg extracts but not for the initial round of replication. Egg extracts undergo periodic oscillations in the level of free calcium. We show here that chelation of calcium in egg extracts or specific inactivation of calcium/calmodulin-dependent protein kinase II (CaMKII) blocks even initial centrosome duplication, whereas inactivation of Cdk2 does not. Duplication can be restored to inhibited extracts by addition of CaMKII and calmodulin. These results indicate that calcium, calmodulin, and CaMKII are required for an essential step in initiation of centrosome duplication. Our data suggest that calcium oscillations in the cell cycle may be linked to centrosome duplication. 相似文献
18.
A sea surface temperature (SST) record based on planktonic foraminiferal magnesium/calcium ratios from a site in the western equatorial Pacific warm pool reveals that glacial-interglacial oscillations in SST shifted from a period of 41,000 to 100,000 years at the mid-Pleistocene transition, 950,000 years before the present. SST changes at both periodicities were synchronous with eastern Pacific cold-tongue SSTs but preceded changes in continental ice volume. The timing and nature of tropical Pacific SST changes over the mid-Pleistocene transition implicate a shift in the periodicity of radiative forcing by atmospheric carbon dioxide as the cause of the switch in climate periodicities at this time. 相似文献
19.
In this study, the direct effects of exterior abscisic acid （ABA） on both calcium distribution of mesophyll cells and cytosolic calcium concentration of guard cells were examined. The distribution of Ca^2＋ localization were observed with calcium antimonate precipitate-electromicroscopic-cyto-chemical methods after treated with ABA and pretreated with ethylene glycol-bis-（2-aminoethylether）-N,N,N＇,N＇-tetraacetic acid （EGTA）, verapamil （Vp）, and trifluoperazine （TFP）. The laser scanning confocal microscopy was used to measure the cytosolic calcium concentrations of guard cells under different treatments. The results showed that the cytosolic Ca^2＋ concentration of mesophyll ceils was induced to increase by ABA, but to decrease in both outside cell and the vacuoles within 10 rain after treatments. The cytosolic calcium concentration of guard cells was increased gradually with the lag in treatment time. However, both EGTA and TFP could inverse those effects, indicating that the increase of cytosolic calcium induced by exterior ABA was mainly caused by calcium influx. The results also showed that calmodulin could influence both the calcium distribution of mesophyll cells and calcium concentration of guard cells. It shows that calmodulin participates in the process of ABA signal transduction, but the mechanism is not known as yet. The changes both calcium distribution of mesophyll cells and calcium concentration of guard cells further proved that the variations of cytosolic Ca^2＋ concentration induced by ABA were involved in the stomatal movements of maize seedlings. 相似文献
20.
Electrophysiological recordings of inward currents from whole cells showed that vascular muscle cells have one type of sodium channel and two types of calcium channels. One of the calcium channels, the transient calcium channel, was activated by small depolarizations but then rapidly inactivated. It was equally permeable to calcium and barium and was blocked by cadmium, but not by tetrodotoxin. The other type, the sustained calcium channel, was activated by larger depolarizations, but inactivated very little; it was more permeable to barium than calcium. The sustained calcium channel was more sensitive to block by cadmium than the transient channel, but also was not blocked by tetrodotoxin. The sodium channel inactivated 15 times more rapidly than the transient calcium channel and at more negative voltages. This sodium channel, which is unusual because it is only blocked by a very high (60 microM) tetrodotoxin concentration but not by cadmium, is the first to be characterized in vascular muscle, and together with the two calcium channels, provides a basis for different patterns of excitation in vascular muscles. 相似文献