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At least 19 recordsLinked to original sources
PubMed1996

Effects of egtazic acid and calcimycin on synthesis of DNA and collagen in cultured human lung fibroblasts.

AIM: To study the effects of egtazic acid (EA) and calcimycin (Cal) on the synthesis of DNA and collagen in cultured human lung fibroblasts (HLF). METHODS: The synthesis of DNA and collagen was determined by measuring the incorporation of [3H]TdR and [3H]proline of HLF respectively. RESULTS: The collagen synthesis increased markedly 24 h after exposure to both EA (0.05-4 mmol.L-1) and Cal (0.25-20 mumol.L-1), and that there was no obvious change in DNA synthesis. After 36-48-h exposure, both DNA and collagen syntheses decreased in the groups of EA (1, 2, and 4 mmol.L-1); the DNA synthesis was also suppressed in Cal groups in a concentration-dependent manner, whereas collagen synthesis decreased only in Cal (10 and 20 mumol.L-1). CONCLUSION: Extracellular Ca2+ influx into fibroblasts increased collagen production, However, the DNA synthesis was suppressed when the cytosolic Ca2+ was too high or too low.

Biological Transport, Active↗
PubMed1999

[Antipyretic action of dexamethasone on egtazic acid-induced fever in rabbits].

The purpose of the present study was to investigate whether the antipyretic effect of dexamethasone (DEX) delivered by intravenous injection (i.v.) on intracerebroventricularly (icv) administered egtazic acid-induced febrile response is relevant to the changes in cytosolic free calcium concentration of the hypothalamus. The colon temperatures were measured by a thermistor and the cytosolic free calcium concentration ([Ca2+]i) in dissociated brain cells was measured by Fura 2-AM. The results demonstrated that the pyretic action of egtazic acid (0.6 mumol, icv) was markedly inhibited by DEX (5 mg/kg, i.v.), but DEX (60-120 mumol/L) did't affect [Ca2+]i in dissociated hypothalamus cells. Actinomycin D, which interferes with gene transcription (3 nmol, icv), completely abolished the antipyretic action of DEX on egtazic acid-induced fever. These findings suggest that the antipyretic action of DEX on egtazic acid-induced fever is related to the activation of certain gene expression in the brain, but not to the changes of transmembrane calcium ion current in hypothalamus neurons.

Analgesics, Non-Narcotic↗
PubMed2000

Effect of protein kinase C on guinea pig sperm acrosome reaction induced by progesterone.

AIM: To investigate the effect of protein kinase C (PKC) on the guinea pig sperm acrosome reaction (AR) induced by progesterone (P4). METHODS: Guinea pig spermatozoa were preincubated in MCM-Ca2+ DF medium at 38.5 degrees C under 5% CO2/air for 6-6.5 h for capacitation, and were then washed through a three-step gradient Percoll, resuspended in MCM-Ca2+ DF and adjusted to 5 x 10(9) cells/L. The AR was assessed by means of phase-contrast microscopy (expressed as percent of AR) 15 min after different reagents were added. RESULTS: In the presence of Ca2+ 2 mmol/L, phorbol 12,13-dibutyrate (PDB) or the permanent synthetic diacylglycerol, 1-oleoyl-2-acetyl-sn-glycerol (OAG) initiated the AR of spermatozoa in a concentration-related manner, whereas staurosporine (STA) exhibited an inhibition of the AR. PDB and OAG significantly enhanced P4-induced AR that was greater than that treated with either agonist separately. STA markedly inhibited the P4-induced AR. The AR induced by PDB was completely antagonized by inclusion of egtazic acid. Also, both egtazic acid and nifedipine antagonized the AR induced by P4 and PDB + P4. In addition, neomycin also prevented the P4-induced AR. This effect could be partly reversed by PDB. CONCLUSION: Activation or inhibition of PKC significantly plays an important role in the signal transduction pathway for the physiological AR.

Acrosome Reaction↗
PubMed2003

Effects of lipopolysaccharides on calcium homeostasis in isolated pancreatic acinar cells of rat.

AIM: To investigate the effects of lipopolysaccharides (LPS, endotoxin) on the calcium content in pancreatic acinar cells and the origin of Ca2+ during calcium overload induced by LPS, further to explore the mechanism of LPS in inducing calcium overload and pancreatic acinar cell injury. METHODS: Male rat pancreatic acinar cells were isolated by collagenase digestion and loaded with Fluo-3/AM, then exposed to varying doses of LPS (from 1 mg/L to 20 mg/L). The dynamic change of [Ca2+]i in single pancreatic acinar cell in the absence and presence of Ca2+ in extracellular fluid was determined by laser scanning confocal microscopy. Cell viability was determined by MTT at different time points after treatment with LPS. RESULTS: Under physiological calcium concentration in extracellular fluid, LPS (10 mg/L) initiated a rapid, concentration-dependent rise in intracellular [Ca2+]i and consequent cell damage (P<0.05). LPS induced a slight rise of [Ca2+]i in the calcium-free extracellular fluid containing egtazic acid 1 mmol/L and addition of extracellular calcium in the presence of LPS resulted in a more immediate and remarkable rise of [Ca2+]i, which reached the peak value within 150 s and maintained the value sustainedly. Egtazic acid attenuated LPS-induced cell damage (P<0.05). The increase in intracellular [Ca2+]i preceded the pathological alteration of pancreatic acinar cells. CONCLUSION: LPS directly induced the injury and the disorder of calcium homeostasis in isolated rat pancreatic acinar cell. Calcium overload is an early event in the pathogenesis of LPS-induced cell damage. Origin of the [Ca2+]i in cytoplasma of pancreatic acinar cells during calcium overload is mainly due to the influx of extracellular Ca2+. Calcium homeostasis disorder may be one of the causes or at least an important mediator of LPS-induced pancreatic acinar cell damage.

Animals↗
PubMed1998

Effect of Coriaria lactone on cytosolic free calcium of cultured neurons from rat cerebral cortex.

AIM: To study the effect of Coriaria lactone (CL) on cytosolic free calcium ([Ca2+]i) of cultured neurons from cerebral cortex. METHODS: Primary neuron culture (14d) and AR-CM-MIC cation measurement system were used, the [Ca2+]i were measured. CL effect was observed by loading egtazic acid. RESULTS: The [Ca2+]i of cultured neurons (99.4-103.4) nmol.L-1 was elevated concentration-dependently by CL (25-500) mumol.L-1 (P < 0.01). This effect disappeared after loading egtazic acid 5 mmol.L-1, but reappeared after adding CaCl2 to 1 mmol.L-1. CONCLUSION: The [Ca2+]i of cultured neurons was elevated by CL, depending on extracellular Ca2+.

Animals↗
PubMed2001

Left ventricular diastolic dysfunction during demand ischemia: rigor underlies increased stiffness without calcium-mediated tension. Amelioration by glycolytic substrate.

OBJECTIVES: The goal of this study was to determine the subcellular mechanism(s) underlying increased left ventricular (LV) diastolic chamber stiffness (DCS) during angina (demand ischemia). BACKGROUND: Increased DCS may result from increased diastolic myocyte calcium concentration and/or rigor. Therefore, we assessed the effects of direct alterations of both calcium-activated tension and high-energy phosphates on increased DCS. METHODS: Demand ischemia was reproduced in isolated, isovolumic, red-cell perfused rabbit hearts by imposing low-flow ischemia and pacing tachycardia. This resulted in increased DCS. Interventions were performed after LV end-diastolic pressure had increased approximately 7 mm Hg. Initially, to determine the effects of altered calcium concentration or myofilament calcium responsiveness, hearts received either: 1) 5 or 14 mmol/L calcium chloride; 2) 8 mmol/L egtazic acid; 3) 5 mmol/L butane-dione-monoxime (BDM); or 4) 50 mmol/L ammonium chloride (NH4Cl). Then, to assess the contribution of decreased high-energy phosphate supply, hearts received 5) glucose (25 mmol/L) and insulin (400 microU/ml). RESULTS: 1) Calcium chloride, 5 and 14 mmol/L, increased LV systolic pressure by 42% and 70%, respectively (p < 0.001), indicating increased calcium-activated tension, but did not further increase DCS, implying intact diastolic calcium resequestration. 2) Egtazic acid reduced LV systolic pressure by 30% (p < 0.001), indicating reduced intracellular calcium, but failed to reduce increased DCS. 3) Butane-dione-monoxime and NH4Cl chloride affected contractile function (i.e., a calcium-driven force) but did not alter increased DCS. 4) Glucose and insulin, which increase high-energy phosphates during ischemia, reduced increased DCS by 50% (p < 0.001). CONCLUSIONS: Increased DCS during demand ischemia was insensitive to maneuvers altering intracellular calcium concentration or myofilament calcium-responsiveness, that is, evidence against an etiology of calcium-activated tension. In contrast, increased glycolytic substrate ameliorated increased DCS, supporting a primary mechanism of rigor-bond formation.

Angina Pectoris↗
PubMed1996

Intracellular Ca2+ during fertilization and artificial activation in mouse oocytes.

AIM: To study the mechanism of oocyte activation in mammals. METHODS: Mouse oocytes arrested at metaphase of the second meiotic division were loaded with Fura 2-AM and then activated with ethanol, calcimycin, electric pulse or fertilization. Intracellular free Ca2+ during activation were measured by Spex AR-CM-MIC cation system. Cortical granule exocytosis after activation was detected under electron microscopy. RESULTS: Sperm penetration initiated a long lasting Ca2+ oscillation in Ca2+ containing IVF medium in mouse ova. The Ca2+ oscillation lasted for over 3-4 h until the ova developed to pronuclear stage. The Ca2+ oscillated faster as extracellular Ca2+ concentration was increased from normal 1.7 mmol.L-1 to 5.0 mmol.L-1 and ceased to oscillate when extracellular Ca2+ was removed. The ova resumed Ca2+ oscillation after transferred back to IVF (Ca2+ 1.7 mmol.L-1). The ova which exhibited Ca2+ oscillation all extruded second polar body and formed pronuclei. Suppression the Ca2+ oscillation by intracellular injection of egtazic acid (2-10 pL, 200 mumol.L-1) blocked the activation of oocytes. Heparin (100 mumol.L-1) injection failed to prevent the Ca2+ oscillation. In artificial activation, ethanol, calcimycin, and a single electric pulse usually induced a monotonic Ca2+ rise and resulted in the activation only in older oocytes (> 18 h after CG injection). Activation of freshly ovulated oocytes required multiple intracellular Ca2+ increases induced by repetitive electric pulses. Artificial activation elicited the similar cortical granule exocytosis in oocytes as occurring at fertilization. Suppression of the intracellular Ca2+ elevation by introduction of egtazic acid into the oocytes blocked the activation process. CONCLUSIONS: The increase of intracellular free Ca2+ is the primary signal responsible for the initiation of oocyte activation but there are distinct differences between fertilization and artificial activation both in Ca2+ change patterns and Ca2+ sources. Young oocytes require oscillatory Ca2+ signals for activation.

Animals↗
PubMed1996

Inhibitory effects of ONO-3708 and S-145 on shape change and aggregation of rabbit platelets induced by STA2.

AIM: To study the mode of inhibition of ONO-3708 and S-145, 2 antagonists of thromboxane A2 (TXA2) receptors, against the rabbit platelet shape change and aggregation induced by stable analogue of TXA2 (STA2). METHODS: The platelet shape change and aggregation were quantified by the light transmission through platelet-rich plasma (PRP) and the intracellular calcium concentration ([Ca2+]i) was measured by fluorescence and imaging. RESULTS: (1) In PRP, STA2 (3 mumol.L-1)-induced aggregation was inhibited by egtazic acid 3 mmol.L-1, ONO-3708 300 mumol.L-1, and S-145 1 mumol.L-1 (P < 0.01), but not by indometacin (Ind) 3 mumol.L-1. The shape change induced by STA2 was inhibited only by S-145 in a concentration-dependent manner. S-145 1 and 3 mumol.L-1 were required to inhibit the shape change and aggregation. (2) The inhibitory effect of S-145, but not ONO-3708, was increased along with the prolongation of preincubation. (3) ONO-3708 lost the inhibitory effect on STA2-induced aggregation after washing, while the inhibitory effect of S-145 was enhanced by prolongation of preincubation and remained after washing. (4) STA2 3 mumol.L-1-induced [Ca2+]i mobilization was unaffected by Ind, partially reduced by ONO-3708 and egtazic acid 3 mmol.L-1 (P < 0.01), but completely inhibited by S-145 (P < 0.01). CONCLUSION: S-145 and ONO-3708 were bound to a different site of the TXA2 receptor.

Animals↗
PubMed2002

Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells.

OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca(2+)](i)) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4-fold. Preincubation with magnesium sulfate (3 x 10(-3) mol/L) for > or = 5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca(2+)](i) in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1998

Mobilization of intracellular Ca2+ modulates activation of Na+/H+ exchange in thrombin-stimulated platelets.

AIM: To study the relationship between intracellular calcium translocation and activation of Na+/H+ exchange in thrombin-stimulated platelets. METHODS: Intracellular Ca2+ ([Ca2+]i) and pH (pHi) were measured by a dual wavelength fluorophotometer with Fura-2 and pH-sensitive probe BCECF. RESULTS: Thrombin 0.1 IU.L-1 elicited an increase in platelet [Ca2+]i and pHi, the maximal increase in [Ca2+]i occurred earlier than the rise in pHi. In Na(+)-free buffers, the Na+/H+ exchange was markedly suppressed without affecting the elevation of [Ca2+]i; while intracellular acidification with nigericin 1 mg.L-1 inhibited the increment of [Ca2+]i. Blockade of Ca(2+)-influx with egtazic acid (EGTA) did not affect cytosolic alkalinization. Depletion of intracellular Ca2+ store with ionomycin in the presence of EGTA, no increment in pHi was observed, the basal value of pHi was even more acidic, this response of pHi to thrombin was rehabilitated after refilling of intracellular Ca2+ store with extracellular Ca2+ 1 mmol.L-1. CONCLUSION: Intracellular Ca2+ mobilization modulated activation of Na+/H+ exchange, which required an effective increment of [Ca2+]i.

Animals↗
PubMed1999

Effect of protopine on cytosolic Ca2+ in rabbit platelets.

AIM: To study the influence of protopine (Pro) on the cytoplasmic free Ca2+ concentration ([Ca2+]i) in rabbit platelets. METHODS: Measurement of [Ca2+]i of platelets in vitro by Fura 2-AM fluorescence technique. RESULTS: In the presence of CaCl2 1 mmol.L-1, Pro 10, 20, and 40 mumol.L-1 attenuated the rise in [Ca2+]i evoked by ADP from (420 +/- 57) to (320 +/- 26), (264 +/- 21), and (180 +/- 14) nmol.L-1, respectively, by arachidonic acid (AA) from (280 +/- 36) to (210 +/- 17), (184 +/- 21), and (143 +/- 16) nmol.L-1, respectively, and by platelet-activating factor (PAF) from (350 +/- 42) to (282 +/- 31), (223 +/- 30), and (165 +/- 15) nmol.L-1, respectively. In the presence of egtazic acid 1 mmol.L-1, Pro 10, 20, and 40 mumol.L-1 reduced the Ca2+ release induced by ADP, AA, and PAF, respectively. Pro 10, 20, and 40 mumol.L-1 also decreased ADP-, AA-, and PAF-induced Ca2+ influx. CONCLUSION: Pro inhibited not only Ca2+ release but also the influx of Ca2+.

Adenosine Diphosphate↗
PubMed1981

Effects of Ca+2 and Mg+2 deprivation of cell shape in cultured ovarian granulosa cells.

After 3 days in culture, rat ovarian granulosa cells assume a flattened epitheloid organization. Ca+2 and Mg+2 deprivation results in cellular rounding which is reversible and was monitored by phase-contrast time-lapse cinematography. Concomitant with the shape change is a dispersion of the structural proteins actin and alpha-actinin. The arrays of large actin-containing bundles (stress fibers) are converted to a diffuse network as observed by electron microscopy. Alpha-actinin, which was observed by immunocytochemistry to be in a periodic array along the actin bundles, is disrupted also and redistributed in the periphery of the cell upon rounding. Measurements made of the culture medium during the rounding process indicate that there is a loss of Ca+2 and Mg+2 from the cell interior. These data led us to speculate that Ca+2 and/or Mg+/ are necessary in order to maintain the integrity of stress fibers and/or restrict the movement of alpha-actinin anchoring sites within the membrane.

Actinin↗
PubMed1979

C3 activation by monosodium urate monohydrate and other crystalline material.

Monosodium urate monohydrate (MSUM) is a potent activator of the complement system as measured by electrophoretic conversion of beta1C to beta1A. Activation of C3 in human serum by MSUM is both time- and dose-dependent. The sensitivity of the assay allows detection of C3 activation by as little as 0.2 mg/ml of MSUM. It was observed that C3 activation is calcium dependent and elimination by both EDTA and EGTA, a finding that demonstrated the major role of the classic pathway of complement activation. Excess calcium or magnesium alone inhibited C3 activation by MSUM in accord with the inhibitory effect of these cations on sensitized sheep cell hemolysis by complement. Heating of MSUM at 200 degrees C for 2 hours removes the water of crystallization such that heated crystals may no longer be considered MSUM. Such treatment has a variable effect on C3 activation. Of the crystals and other material studied, only zymosan was more potent than MSUM in activating C3. Calcium prophosphate dihydrate and hydroxyapatite activated significant amounts of C3. Asbestos, glass wool, or a variety of microcrystalline steroids activated little or no C3.

Calcium↗
PubMedDate not supplied

Magnesium-dependent induction of phagocytosis-associated chemiluminescence of adherent human polymorphonuclear leukocytes by non-opsonized zymosan.

A severe dysfunction in the cellular response of human polymorphonuclear leukocytes (PMNL) to non-opsonized zymosan was observed under a deficiency of extracellular Mg2+. The phagocytosis-association native (luminol-independent) luminescence (NL), as well as luminol-dependent luminescence (LDL) (detected simultaneously and discriminated by spectral methods), was strongly inhibited. Apart from a general decrease of total light production, a Mg2+-concentration-dependent delay of the maximum of NL and LDL was observed. A disorder in recruitment of activated membrane-bound NADPH-oxidase of PMNL is suggested. The presence of extracellular Ca2+ did not compensate for the Mg2+ deficit. In the presence of Mg2+ only a slight Ca2+-dependent reduction of NL was obtained, but Ca2+ seemed to selectively promote LDL. This may indicate a positive influence of Ca2+ on the myeloperoxidase release from the cells. Experiments with the metalions-chelating agents EDTA and EGTA, which complex Mg2+ to differing extents, confirmed the important role of Mg2+ in PMNL-activation by non-opsonized zymosan.

Calcium↗
PubMed1990

Control of astrocyte volume by intracellular and extracellular Ca2+.

Astrocytes from primary culture were exposed to conditions that affect intracellular and extracellular Ca2+ concentrations. Astrocyte cell volume was increased approximately 16% after a 30 min exposure to isoosmotic phosphate-buffered saline (PBS) containing the Ca2+ buffer EDTA. Cell volume returned to control values within 30 min of resuspension in normal PBS. Cellular calcium content was not affected by these treatments; however, the recovery of normal cell volume following EDTA exposure was inhibited by 0.1-1.0 mM quinine HCl in a dose-dependent fashion suggesting that a potassium channel controlled by the intracellular Ca2+ concentration is important in this volume response. Intracellular accumulation of an exogenous Ca2+ buffer, BAPTA, also produced cell swelling that persisted following resuspension in normal PBS. Lowering the extracellular Ca2+ concentration with EDTA enhanced the swelling of BAPTA-loaded cells. These data suggest that conditions leading to a decrease in free intracellular Ca2+ concentration may influence astrocyte volume by a mechanism similar to that described in other cell types.

Animals↗
PubMed1984

Separation of macrophages from mouse peritoneal exudate cells with substrata coated with chemically modified collagens.

A cell-separation technique was designed on the basis of specific interaction between macrophages and chemically modified collagens in the presence of serum. When unseparated mouse peritoneal exudate cells containing approximately 50% macrophages and 50% lymphocytes were incubated in dishes coated with unmodified and chemically modified collagens, only macrophages adhered more rapidly and in greater numbers to succinylated and methylated collagen than to unmodified collagen. The adherent macrophages could be easily detached from the substrata by divalent cation chelating agents. The purity and recovery of macrophages separated by this method were approximately 92-94% and 41-48%, respectively.

Animals↗
PubMed1985

Release of galactosyltransferase from peritoneal macrophages during acute inflammation.

Peritoneal cells harvested from mice injected with Salmonella enteritidis or thioglycollate released large amounts of galactosyltransferase (GT), but not sialyltransferase, into their culture supernatants. Maximum release of GT (using ovalbumin as acceptor) occurred from cells harvested 2-4 days after primary injection, but little GT was released from cells elicited by a secondary injection of salmonella or ovalbumin in sensitised mice or during intraperitoneal allogeneic reactions. Enzyme release in culture did not parallel GT levels in serum. Most enzyme was released by large, poorly adherent, macrophage-enriched, Fc receptor-bearing peritoneal cells of low density. Normal monocytes, bone marrow cells, and platelets also produced large amounts, and normal spleen cells or polymorphonuclear leukocytes moderate amounts, of GT. Lymphocytes, dead cells, mast cells, red blood cells, or whole populations of lymph node and thymus cells released very low levels of enzyme. Very little GT was bound to the cell surface and was not passively absorbed from serum or platelets. Release of GT was prevented at 4 degrees C but was not markedly affected by a variety of metabolic inhibitors except pretreatment of the cells with thrombin, which increased release and trypsin which decreased release.

Animals↗