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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat cardiac muscle was dissociated into single cells by a coronary perfusion technique with collagenase and hyaluronidase in a Ca-free medium. Retention of the cylindrical shape of isolated muscle cells could be achieved by regulation of [Ca2+]0 and temperature. Cells kept at 4 degrees C, and 0-01 mM CaCl2 remained cylindrical for more than a week and contracted spontaneously upon warming at 37 degrees C. At [Ca2+]0 between 0-1-2 mM and 37 degrees C, cells underwent contracture and rounded up. Scanning (SEM) and transmission electron microscopy were used to analyze the structure of cylindrical and rounded muscle cells. The extracellular aspect of the sarcolemma at lateral cell surfaces and intercalated disc regions were clearly revealed for SEM analysis. Both the distribution and number of T-tubule openings on the surfaces can be estimated and a three-dimensional description of the intercalated disc obtained. This study reveals that isolated adult heart cells are extremely sensitive to [Ca2+]0, but with careful control of this cation, this preparation should be helpful in the analysis of both sarcolemmal structure and the pathological changes which accompany myocardial injury.
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PMID:Studies of isolated adult rat heart cells: the surface morphology and the influence of extracellular calcium ion concentration on cellular viability. 20 Oct 46

To study limb vascular responses in man to elevations in plasma calcium concentrations, we infused test isosmolar solutions of CaCl2 (0.115, 0.230, and 0.460 meq calcium/min) and NaCl and control isosmolar solutions of NaCl into the brachial arteries of 10 normotensive men and eight men with essential hypertension of mild to moderate severity. Limb blood pressures were monitored, limb blood flow was measured by indicator-dilution, and limb vascular resistance was calculated as mm Hg/ml flow/min/100 cm3 limb volume. Measured concentration of calcium in limb venous plasma during infusion of 0.460 meq calcium/min was 11.5 +/- 0.8 meq/liter (mean +/- SEM) with individual values ranging up to 20 meq/liter. Changes in limb venous serum sodium, potassium, magnesium, and osmolality were similar during control and CaCl2 infusions. Decreases in limb venous blood hematocrit during CaCl2 infusions were the same or greater than those during control infusions. The infusions did not significantly change systemic blood calcium concentration or blood pressures. Limb blood flow decreased and resistance increased in response to CaCl2. Increments averaging as little as 2.2 meq/liter elevated limb resistance by about 45%. Log dose-response curves were linear. Responses did not differ in normotensives and hypertensives (P greater than 0.8). We conclude that the vascular response to acute elevation of plasma calcium concentrations up to 20 meq/liter in the limb oman is an impressive vasoconstriction. We found no evidence for abnormal vascular responses to calcium in essential hypertensive men.
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PMID:Similar vasoconstrictor responses to calcium in normotensive and esssential hypertensive men. 109 55

It is very important to find suitable reaction conditions to attain a high specific binding (specific/total binding) in the receptor binding study. Membrane homogenates of pig choroid plexus are known to have exclusively serotonin (5-hydroxytryptamine, 5-HT) receptor of the subtype 5-HT1c. In this study, we used the membrane preparation of pig choroid plexus tissue and the specific binding of [3H]5-HT was 72-84% to serotonin receptor subtype 5-HT1c, as defined by the inhibition of 1 uM 5-HT, when a radioligand concentration of 0.5 nM of [3H]5-HT was used in the assay. Analysis of the properties of specific [3H]5-HT binding in pig choroid plexus tissue membrane preparation revealed linear Scatchard plots. In Tris-HCl buffer without CaCl2, pargyline or ascorbic acid, high average of affinity dissociation constant (Kd) of 1.3 +/- 0.2 nM (SEM, n = 4) and also a high average of receptor density (Bmax) of 284 +/- 12 fmol/mg of protein were found. Pig choroid plexus proves to be a good material for 5-HT1c receptor binding study.
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PMID:Serotonin (5-HT1c) receptors in pig choroid plexus. 184 41

The present study adapted the overwintering strategy employed by freeze-tolerant amphibians and reptiles to freeze-preserve the isolated rat heart. The heart was flushed with a cardioplegic solution and supercooled to -1.2 and -3 degrees C. Then freezing was induced by inoculation of ice crystal. The viability of the heart explant was assessed after reanimation by the isolated working heart perfusion. There was no recovery of function in hearts flushed with solution containing 0.28 mM CaCl2. Lowering the concentration of CaCl2 to 0.15 mM, however, rendered good functional return. Furthermore, inclusion of 50 mM glycerol in the flush solution dramatically improved functional preservation. Under the best conditions defined here, the recoveries of aortic flow, coronary flow, cardiac output, systolic pressure, and work in hearts stored at -1.2 degrees C for 3 h were 72.8 +/- 6.8, 87.2 +/- 4.2, 77.6 +/- 5.4, 83.4 +/- 2.8, and 66.6 +/- 5.9% (mean +/- SEM, n = 8) of the unstored control levels, respectively. The myocardial ice content was 18.6 +/- 5.4% (n = 5) of tissue water. Prolonging the storage time to 5 h increased the ice content to 45.3 +/- 8.1% and reduced the recovery of cardiac output to 23 +/- 11% of the control value (mean +/- SEM, n = 5). Hearts frozen at -3 degrees C for 1.5 h showed 29.4 +/- 8.7% (n = 3) of control cardiac output during reperfusion. This novel approach may provide an opportunity to advance our knowledge about freezing preservation of not only the heart but other solid organs as well.
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PMID:Freezing preservation of adult mammalian heart at high subzero temperatures. 207 Jun 19

Gap junctional conductance (gj) between cardiac ventricular myocyte pairs is rapidly, substantially, and reversibly reduced by sarcoplasmic acidification with CO2 when extracellular calcium activity is near physiological levels (1.0 mM CaCl2 added; 470 microM Ca++). Intracellular calcium concentration (Cai), measured by fura-2 fluorescence in cell suspensions, was 148 +/- 39 nM (+/- SEM, n = 6) and intracellular pH (pHi), measured with intracellular ion-selective microelectrodes, was 7.05 +/- 0.02 (n = 5) in cell pair preparations bathed in medium equilibrated with air. Cai increased to 515 +/- 12 nM (n = 6) and pHi decreased to 5.9-6.0 in medium equilibrated with 100% CO2. In air-equilibrated low-calcium medium (no added CaCl2; 2-5 microM Ca++), Cai was 61 +/- 9 nM (n = 13) at pHi 7.1. Cai increased to only 243 +/- 42 nM (n = 9) at pHi 6.0 in CO2-equilibrated low-calcium medium. Junctional conductance, in most cell pairs, was not substantially reduced by acidification to pHi 5.9-6.0 in low-calcium medium. Cell pairs could still be electrically uncoupled reversibly by the addition of 100 microM octanol, an agent which does not significantly affect Cai. In low-calcium low-sodium medium (choline substitution for all but 13 mM sodium), acidification with CO2 increased Cai to 425 +/- 35 nM (n = 11) at pHi 5.9-6.0 and gj was reduced to near zero. Junctional conductance could also be reduced to near zero at pHi 6.0 in low-calcium medium containing the calcium ionophore, A23187. The addition of the calcium ionophore did not uncouple cell pairs in the absence of acidification. In contrast, acidification did not substantially reduce gj when intracellular calcium was low. Increasing intracellular calcium did not appreciably reduce gj at pHi 7.0. These results suggest that, although other factors may play a role, H+ and Ca++ act synergistically to decrease gj.
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PMID:Gap junctional conductance between pairs of ventricular myocytes is modulated synergistically by H+ and Ca++. 211 74

Pretreatment of the dentinal surface with acidic solution is now considered to be necessary to obtain strong bonding between dentin and resin materials. Effects of various surface treatments for dentin bonding on dentinal smear removal have been reported by SEM observation. In this study, changes of dentin permeability after the surface treatments were measured using Pashley's technique. Forty-second treatments with either phosphoric acid gel, aqueous phosphoric acid, 10-3 solution or aqueous 10-20 Ca solution (10% citric acid containing 20% CaCl2) produced greater increases in dentin permeability compared with the treatments using either 10-20 Ca gel, Tenure Conditioner, Scotchprep or Gluma 2 for 40 seconds. Treatments with primers including adhesive monomers such as Scotchprep and Mirage Conditioner also increased the dentin permeability by removal of the smear layers and smear plugs. Application of a bonding agent (Clearfil Photobond) for 1 minute did not remove the smear plugs and the dentin permeability remained the same as before the treatment. The changes in dentin permeability were not predictable by SEM observation in some cases.
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PMID:[Effect of various pretreatments for dentin bonding on dentin permeability]. 213 14

Ca and phenylephrine, both of which increase mean arterial pressure (MAP), are often administered concurrently during resuscitation of critically ill patients. To determine whether the response to phenylephrine is potentiated by Ca administration, we studied eight adult patients 24 h after aortocoronary bypass surgery. Each patient received three doses of phenylephrine (150, 300, and 450 ng/kg.min), administered both with and without CaCl2 (5 mg/kg bolus followed by a 2-mg/kg.h infusion). Phenylephrine alone at 150, 300, and 450 ng/kg.min increased MAP by 2%, 6%, and 17%, respectively. Ca alone increased serum ionized Ca levels from 1.00 +/- .03 (SEM) to 1.20 +/- .02 mM (p less than .05) and increased MAP from 84 +/- 1 to 90 +/- 2 mm Hg (p less than .05), but had no effect on cardiac index (CI). When administered concurrently with Ca, phenylephrine at 150, 300, and 450 ng/kg.min increased MAP by 6%, 7%, and 13%, respectively. Phenylephrine had no effect on CI, pulmonary capillary wedge pressure, CVP, or heart rate whether or not it was administered with Ca. We conclude that concomitant Ca administration does not augment the hypertensive response to phenylephrine in normotensive patients recovering from open heart surgery.
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PMID:Calcium does not augment phenylephrine's hypertensive effects. 234 49

The thrombolytic dose-response effectiveness and pharmacokinetics of tissue-type plasminogen activator (rt-PA) was evaluated in anesthetized, open-chest dogs instrumented for the measurement of systemic hemodynamics. Intracoronary thrombi were formed by injecting thrombin (100 U) and CaCl2 (50 microM) into a cannulated, isolated segment of the left anterior descending coronary artery (LAD). Coronary blood flow was measured by placing an electromagnetic flow probe proximal to the LAD thrombus. Thirty minutes after formation of a stable LAD thrombus, intravenous infusion of rt-PA was given at rates of 0.5, 1, 2, 4, or 8 micrograms/kg/min (n = 8/dose) for 60-90 min, and the animals were followed for an additional 30 min. In vehicle-treated animals, residual thrombus wet weight, determined at the end of the experiment, was 30 +/- 4 mg (mean +/- SEM, n = 8) and spontaneous reperfusion did not occur. The rt-PA produced a dose-related increase in the number of animals reperfusing, a decrease in the time to reperfusion, and a decrease in residual thrombus weight, but had no effect on systemic hemodynamics. The increase in infusion rate from 0.5 to 4 micrograms/kg/min resulted in a linear increase in both the steady-state rt-PA plasma concentration and the area under the rt-PA plasma concentration versus time curve (n = 3-5 animals/dose); between the infusion rates of 4 and 8 microgram/kg/min there was a disproportionate increase in both these parameters that was due to a decrease in the total systemic clearance of rt-PA. The postdosing elimination half-life (t1/2 alpha) did not differ significantly at any dose of rt-PA, and the pooled half-life (t1/2 alpha) for all doses of rt-PA was 2.36 +/- 0.12 min (n = 19).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evaluation of the acute hemodynamic effects and pharmacokinetics of coronary thrombolysis produced by intravenous tissue-type plasminogen activator in the anesthetized dog. 246 3

The effect of calcium on plasma atrial natriuretic factor (ANF) concentration was determined in spontaneously hypertensive rats (SHR) and their control, Wistar-Kyoto (WKY) rats. CaCl2 10.5 mg (0.095 mmol) in 0.54 ml 5% glucose or an equal volume of vehicle alone was infused intravenously for 30 minutes into conscious precannulated SHR (vehicle, n = 16; CaCl2, n = 16) and WKY rats (vehicle, n = 25; CaCl2, n = 15). Direct systolic blood pressure was measured throughout the infusion period. Blood samples for serum total calcium and plasma ANF were obtained at the end of each experiment. The systolic blood pressure did not change significantly during infusion of the vehicle or CaCl2 in either strain. No significant difference was observed in serum total calcium concentration between SHR and WKY rats after vehicle (9.8 +/- 0.1 [mean +/- SEM] mg/dl vs. 10.0 +/- 0.1) or after CaCl2 infusion (12.2 +/- 0.3 vs. 12.2 +/- 0.2). Plasma ANF concentrations after both vehicle and CaCl2 infusion were significantly higher in SHR than in WKY rats (vehicle, 211 +/- 24 pg/ml vs. 129 +/- 11, p less than 0.05; CaCl2, 395 +/- 21 vs. 278 +/- 33, p less than 0.05). There were high degrees of correlation between serum total calcium and plasma ANF both in SHR (r = 0.77, p less than 0.001) and in WKY rats (r = 0.76, p less than 0.001). No significant difference was observed in the slopes of the regression lines of ANF as a function of the serum total calcium concentration between SHR and WKY rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Calcium infusion increases plasma atrial natriuretic factor in spontaneously hypertensive rats. 252 28

Direct measurements of free intracellular calcium (Ca)i are needed for an understanding of the regulation of contractility. An on-line measurement of (Ca)i with Ca-selective microelectrodes in intact muscle strips provides a suitable means of investigating this problem, although considerable methodologic difficulties exist. Measurements of (Ca)i concentrations during muscle contraction have been carried out by different methods such as Ca-binding techniques and aequorin luminescence, but remain unsatisfying, since they were not performed on intact muscle strips. The authors' measurements were carried out with Ca-selective microelectrodes on rat papillary muscles (stretched to optimal length in a perfusion bath of 1.54 mL at 30 degrees C). The impalement of electrodes was considered adequate when the heights of Ca-electrode potential and membrane potential remained constant for more than twenty minutes. For provoking contractile responses, the authors replaced the normal Tyrode solution by a caffeine-containing contracture solution (content in mM: 0 NaCl [choline], 4 CaCl2, 30 KCl, 25 caffeine, 1.05 MgCl2). Ca-selective microelectrodes were calibrated before and after each measurement and only those impalements were taken as adequate that showed identical calibration curves before and after the experiment. They measured the (Ca)i at 20%, 50%, and 80% of maximal contractile force and obtained (Ca)i concentrations of 1.1 +/- 0.3 microM (at 20%), 3.6 +/- 1.2 microM (at 50%), and 11.8 +/- 0.27 microM (at 80%) (n = 6, +/- SEM). These results represent the fist on-line measurements of the myocardial (Ca)i concentrations with Ca++-selective microelectrodes in intact muscle strips during various degrees of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Free calcium in rat papillary muscle at contraction assessed with Ca-selective microelectrodes. 275 65


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