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PubMed1995

The role of calcium in the hydrolysis of the organophosphate paraoxon by human serum A-esterase.

Human serum A-esterase is a calcium-dependent enzyme that hydrolyzes the organophosphate paraoxon by an Ordered Uni Bi kinetic mechanism. Incubation of various concentrations of calcium chloride with human serum A-esterase resulted in corresponding changes in appk3 and appE for the reaction, while appk2 was unaffected. Carboxyglutamic acid (CAG) prevented calcium chloride from altering appk3, but not appE. Similarly CAG reduced the calcium-stimulated nonenzymatic hydrolysis of paraoxon, as well as the calcium-stimulated de-phosphorylation of chymotrypsin phosphorylated by paraoxon. These results suggest that calcium plays two roles in the hydrolysis of paraoxon by A-esterase. Firstly, calcium is required in order to maintain an active site. In this capacity calcium might participate directly in the catalytic reaction, or it might be required in order to maintain the appropriate confirmation of the active site. And secondly, free calcium (or calcium weakly associated with A-esterase) facilitates the removal of diethyl phosphate from A-esterase, probably by polarizing the P = O bond of the diethyl phosphate-A-esterase intermediate, thereby rendering phosphorus more susceptible to nucleophilic attack by hydroxide ions.

Adult↗
PubMed2000

Effect of magnesium on calcium-dependent brain function that prolongs ethanol-induced sleeping time in mice.

The effect of intracerebroventricular (i.c.v.) administration of magnesium on calcium- and dopamine-dependent brain function was investigated behaviorally and biochemically. The duration of ethanol-induced sleeping time in mice was prolonged following i.c.v. administration of calcium chloride (10 micromol/kg) or dopamine (30nmol/mouse); however, it was not affected by magnesium chloride (10 or 40 micromol/kg). The ability of calcium to prolong ethanol-induced sleeping time was inhibited by the administration of magnesium chloride. The brain dopamine level in mice was significantly increased following i.c.v. administration of calcium chloride. Taking into consideration these results and those from previous studies, it is suggested that calcium enhances dopamine synthesis in the brain through a calmodulin-dependent system, and the increase in dopamine level prolongs ethanol-induced sleeping time. However, magnesium inhibits dopamine release. Therefore, magnesium may inhibit calcium-dependent brain function through dopaminergic neurons, and consequently reduce the effect of calcium on ethanol activity.

Animals↗
PubMed1998

Distinct roles for sodium, chloride, and calcium in excitotoxic dendritic injury and recovery.

The postsynaptic neuronal dendrite is selectively vulnerable to hypoxic-ischemic brain injury and glutamate receptor overactivation. We explored the glutamate receptor pharmacology and ionic basis of rapid, reversible alterations in dendritic shape which occur in cultured neurons exposed to glutamate. Dendrite morphology was assessed with the fluorescent membrane tracer, DiI, or immunofluorescence labeling of the somatodendritic protein, MAP2. Cortical cultures derived from 15-day-old mouse embryos underwent segmental dendritic beading when exposed to NMDA, AMPA, or kainate, but not to metabotropic glutamate receptor agonists. Varicosity formation in response to NMDA or kainate application was substantially attenuated in reduced sodium buffer (substituted with N-methyl-D-glucamine). Furthermore, veratridine-induced sodium entry mimicked excitotoxic alterations in dendrites and additionally caused varicosity formation in axons. Solutions deficient in chloride (substituted with Na methylsulfate) and antagonists of chloride-permeable GABA/glycine receptors reduced NMDA- or kainate-induced varicosity formation. An increase in dendrite volume was observed as varicosities formed, and varicosity formation was attenuated in sucrose-supplemented hypertonic media. Despite marked structural changes affecting virtually all neurons, dendrite shape returned to normal within 2 h of terminating glutamate receptor agonist application. Neurons exposed to kainate recovered more rapidly than those exposed to NMDA, and neurons exposed to NMDA in calcium-free buffer recovered more rapidly than cells treated with NMDA in normal buffer. While sodium, chloride, and water entry contribute to excitotoxic dendritic injury acutely, calcium entry through NMDA receptors results in lasting structural changes in damaged dendrites.

Animals↗
PubMed1985

In vitro inhibition of the activation of the human complement and coagulation systems by chloroquine.

The ability of chloroquine to inhibit the activation of the complement and coagulation systems was investigated. The activation of the classical pathway of complement by antibody coated sheep erythrocytes and aggregated IgG was blocked by chloroquine. Similarly, it prevented normal rabbit erythrocytes and zymosan from activating the the alternative pathway of complement. The activation of C3 by immune complexes of different solubilities also was inhibited by this drug. In addition, it abrogated the clotting of plasma by calcium chloride and thrombin. This effect could be reversed by the addition of excess thrombin but not of calcium chloride. It is suggested that the inhibition of these two important phlogistic mediator systems of inflammation may contribute to the anti-inflammatory property of chloroquine.

Animals↗
PubMed2006

Characterization of calcium alginate beads containing structurally similar drugs.

The aim of this study was to investigate the characteristics of alginate beads prepared by ionotropic gelation in which structurally similar drugs were incorporated. For this purpose theophylline and theobromine were selected as model drugs. The influence of incorporated drugs on bead characteristics such as size, shape, and morphology, as well as encapsulation efficiency, was examined. It was found that theobromine as well as theophylline content in beads significantly decreased with increasing hardening time due to drug diffusion into the hardening media. In theobromine beads the drug content was extremely improved by dropping the alginate and drug solution into an acidic calcium chloride solution, while theophylline content was to some extent improved by the hardening of beads in a calcium chloride solution saturated with the drug. The most evident difference between theophylline and theobromine beads was in their shape and morphology. Theobromine beads were round, while theophylline ones had an irregular shape with an extremely wrinkled surface. The distinction in shape was highly dependent on drug content. Additionally, it was demonstrated that beads' shape was dependent on preparation conditions as well. On the basis of x-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) analyses and scanning electron microscope (SEM) photographs it was found that the most of the drug in bead was present in an amorphous state. Therefore, it is suggested that some drug-alginate interactions could be present in beads and might be responsible for the different shape of theophylline and theobromine beads. Thus it can be concluded that the preparation of beads by ionotropic gelation cannot be generalized even though structurally similar drugs are incorporated.

Alginates↗
PubMed1990

[Sudden cardiac arrest during percutaneous nephrostolithotomy (PNL) under epidural anesthesia].

There have been few major complications of percutaneous nephrostolithotomy (PNL) reported. We recently experienced cardiac arrest during PNL under epidural anesthesia. The patient was a 52 year old man weighing 64 kg who had been suffering from right renal pelvic stone for years. He was scheduled for PLN under epidural anesthesia. Analgesia was obtained to the level of Th6. The operation proceeded uneventfully for about 60 min. By this time, he suddenly complained nausea, and hypotension with bradycardia occurred. Blood pressure and pulse rate returned immediately to the normal level by IV atropine and ephedrine. But after three minutes, blood pressure and pulse rate went down again. This hypotension with bradycardia was unresponsive to epinephrine, calcium chloride and sodium bicarbonate. This was followed by asystole. Resuscitation was successful with the addition of epinephrine, calcium chloride, and sodium bicarbonate about 15 min after cardiac massage had started. The patient was, on the fifth postoperative day, with no evidence of impairment of renal, cardiac and respiratory functions but a slight impairment of neurologic function. Several possible causes for this cardiac arrest and anesthetic management of percutaneous nephrostolithotomy are discussed.

Anesthesia, Epidural↗
PubMed1986

New theory on the pathogenesis of acute myocardial infarction.

Autopsy studies of hearts from 140 patients who had suffered acute myocardial infarction (AMI) and 26 cases of sudden coronary death revealed two distinct types of myocardial cell death: "kinetic cell death" (KD) and "static cell death" (SD). In KD, the predominant type of cell death in AMI-myofibrils disintegrated through alternating overcontraction and overextension. KD was found not only in patients having died after some time had elapsed from the onset of AMI, but also in cases of sudden coronary death. Muscle fibers in SD, which by contrast began to appear at least seven hours after the onset of AMI, characteristically preserved cross striations, while their nuclei were pyknotic or had already disappeared. Such fibers were observed only in territories peripheral to occlusive coronary thrombus, a secondary rather than a primary event that takes place during the course of AMI. As a result of the above observations, we were able to produce a new experimental model of AMI using mongrel dogs. As a preparatory procedure we first injected them intravenously with 2% calcium chloride at a constant rate for 90 or 120 minutes, and then with a sudden injection of caffeine, calcium chloride and catecholamine in order to induce KD. In contrast, ligation of the intraventricular coronary artery near its origin caused SD of myocardial fibers in the dependent territories. Overall results led us to conclude that AMI is initiated by instantaneous overcontraction of myocardial fibers, resulting in their KD, a phenomenon that could be called "myocardial self-destruction."

Adult↗
PubMed1992

Selectivity of a CaCl2 continuous infusion screening method in rats.

In albino rats the combined use of two methods based on a continuous perfusion of aconitine nitrate (0.15 mg/ml) or calcium chloride (0.4 M) demonstrated the selectivity of the calcium chloride-induced dysrhythmias model. This rapid screening was carried out with antidysrhythmic agents according to the Vaughan-Williams's classification (1): quinidine (class I) 5 mg/kg; atenolol (class II) 2 mg/kg; amiodarone (class III) 10 mg/kg and verapamil (class IV) 2 mg/kg. A compound synthesized in our laboratory was used to verify model selectivity.

Aconitine↗
PubMed2004

Crystal structures of dihydroxyacetone and its derivatives.

The crystal and molecular structures of three crystalline forms of the dihydroxyacetone dimer, C6H12O6, DHA-dimer: alpha (1a), beta (1b), and gamma (1c), the hydrated calcium chloride complex of dihydroxyacetone monomer, CaCl2(C3H6O3)(2) x H2O, CaCl2(DHA)2 x H2O (2a), the tetrahydrated calcium chloride complex of dihydroxyacetone monomer, CaCl2(C3H6O3) x 4H2O, CaCl2(DHA) x 4H2O (2b), the dihydroxyacetone monomer, C3H6O3, DHA (2c), and dihydroxyacetone dimethyl acetal, C5H12O4, (MeO)2DHA (3) are described. Compounds 1a and 2b crystallize in the triclinic system, and 1b,c, 2a,c, and 3 are monoclinic. Molecules of all forms of dihydroxyacetone dimer 1a,b, and 1c are the trans isomers, with the 1,4-dioxane ring in the chair conformation and the hydroxyl and hydroxymethyl groups in axial and equatorial dispositions, respectively. The Ca2+ ions in 2a and 2b are bridged by the carbonyl O atoms from two symmetry-related DHA molecules to form centrosymmetric dimers with Ca...Ca distance of 4.307(2)A in 2a and 4.330(2) and 4.305(2)A in two crystallographically independent dimers in 2b. DHA molecules coordinate to the Ca2+ ions by hydroxyl and carbonyl oxygen atoms. The eight-coordinate polyhedra of Ca2+ are completed by water molecule and Cl- ion in 2a and by four water molecules in 2b. The dihydroxyacetone molecules in 2a,b, and 2c are in an extended conformation, with both hydroxyl groups being synperiplanar (sp) to the carbonyl O atom. All hydroxyl groups in 2c (along with water molecules in 2a and 2b) are involved as donors in medium strong and weak intermolecular O-H...O hydrogen bonding. Some of them, as well as carbonyl O atoms or Cl- ions in 2a and 2b, act as acceptors in C-H...O (and C-H...Cl) hydrogen interactions.

Crystallography, X-Ray↗
PubMed1980

The diuretic effect of secretin in man.

Six young healthy male students were studied with an intravenous infusion of 50 ml/h saline for three 2 h periods. In the second 2 h period pure natural secretin was added to the saline infusion in a dose of 2 CU/kg . h. Urine was collected separately in the three 2 h periods, and blood was drawn every 1 h. Urinary water, sodium, potassium, chloride, calcium, creatinine and solute excretion increased significantly during the 2-h secretin period. The clearance of sodium, potassium, chloride, calcium and solutes as a percentage of glomerular filtration rate (creatinine clearance) increased significantly, whereas tubular reabsorption of sodium as a percentage of filtrated sodium decrased significantly during secretin infusion. Even though plasma secretin remained elevated in the first half of the last 2 h control period, no diuretic effect was noted in this period. It would appear therefore that the diuretic effect of secretin most likely is a pharmagological effect only.

Body Water↗
PubMed1996

A biologic function for an "orphan" messenger: D-myo-inositol 3,4,5,6-tetrakisphosphate selectively blocks epithelial calcium-activated chloride channels.

Inositol phosphates are a family of water-soluble intracellular signaling molecules derived from membrane inositol phospholipids. They undergo a variety of complex interconversion pathways, and their levels are dynamically regulated within the cytosol in response to a variety of agonists. Relatively little is known about the biological function of most members of this family, with the exception of inositol 1,4,5-trisphosphate. Specifically, the biological functions of inositol tetrakisphosphates are largely obscure. In this paper, we report that D-myo-inositol 3,4,5,6-tetrakisphosphate (D-Ins(3,4,5,6)P4) has a direct biphasic (activation/inhibition) effect on an epithelial Ca(2+)-activated chloride channel. The effect of D-Ins(3,4,5,6)P4 is not mimicked by other inositol tetrakisphosphate isomers, is dependent on the prevailing calcium concentration, and is influenced when channels are phosphorylated by calmodulin kinase II. The predominant effect of D-Ins(3,4,5,6)P4 on phosphorylated channels is inhibitory at levels of intracellular calcium observed in stimulated cells. Our findings indicate the biological function of a molecule hitherto considered as an "orphan" messenger. They suggest that the molecular target for D-Ins(3,4,5,6)P4 is a plasma membrane Ca(2+)-activated chloride channel. Regulation of this channel by D-Ins(3,4,5,6)P4 and Ca2+ may have therapeutic implications for the disease states of both diabetic nephropathy and cystic fibrosis.

Adenosine Triphosphate↗
PubMed1979

Physical studies on isolated human prothrombin fragment-2. Comparisons with human prothrombin fragment-1.

Variation of pH strongly affects the fluorescence intensity of human prothrombin fragment-1 in a manner suggesting contributions from a number of protropic equilibria including groups with apparent pKa values near 3.0. These results suggest a structural role for pK1a of gamma-carboxyglutamic acid noieties. Added calcium ions (9 mM calcium chloride) quench the fluorescence titration curve uniformly above pH 4. Below pH 4, however, the titration curve in the presence of calcium ions suggests that calcium-ion-dependent processes leading to fluorescence quenching are pH-dependent. Upon back titration of human fragment-1, from pH 9, hysteresis is observed. Human prothrombin fragment-2 fluorescence titration curves are relatively broad at low pH suggesting the titration of normal carboxyl groups. The titration curves of fragment-2 are not affected by the presence of calcium ions, and hysteresis occurs upon back titration from low pH values. Circular dichroism (CD) Cotton effects appear at 232 nm and 280 nm and a trough appears at 203 nm in the CD spectrum of human prothrombin fragment-2. The Cotton effects in the region from 230 nm to 300 nm are sensitive to pH, ellipticity values at 232 nm increasing from approximately 300 at pH 2.5 to 1300 (degree-cm/decimole) at neutral pH and finally become negative at high pH values. In contrast to fragment-1, at neutral pH the fragment-2 Cotton effect at 232 nm is insensitive to the presence of 8 mM calcium chloride.

Calcium↗
PubMed2002

The large conductance potassium channel beta-subunit can interact with and modulate the functional properties of a calcium-activated chloride channel, CLCA1.

We have recently compared the biophysical and pharmacological properties of native Ca(2+)-activated Cl(-) currents in murine portal vein with mCLCA1 channels cloned from murine portal vein myocytes (Britton, F. C., Ohya, S., Horowitz, B., and Greenwood, I. A. (2002) J. Physiol. (Lond.) 539, 107-117). These channels shared a similar relative permeability to various anions, but the expressed channel current lacked the marked time dependence of the native current. In addition, the expressed channel showed a lower Ca(2+) sensitivity than the native channel. As non-pore-forming regulatory beta-subunits alter the kinetics and increase the Ca(2+) sensitivity of Ca(2+)-dependent K(+) channels (BK channels) we investigated whether co-expression of beta-subunits with CLCA1 would alter the kinetics/Ca(2+) sensitivity of mCLCA1. Internal dialysis of human embryonic kidney cells stably expressing CLCA1 with 500 nM Ca(2+) evoked a significantly larger current when the beta-subunit KCNMB1 was co-expressed. In a small number of co-transfected cells marked time dependence to the activation kinetics was observed. Interaction studies using the mammalian two-hybrid technique demonstrated a physical association between CLCA1 and KCNMB1 when co-expressed in human embryonic kidney cells. These data suggest that activation of CLCA1 can be modified by accessory subunits.

Animals↗
PubMed1976

Prevention by calcium administration of reserpine action on rat brain noradrenaline stores: a reappraisal.

The conditions under which pretreatment with a calcium salt may prevent the action of reserpine on brain noradrenaline stores in the rat were investigated. The results show that only after subcutaneous administration of reserpine in the same site as a previous CaCl2 injection, was the action of reserpine prevented and reduced levels of this drug were found in the brain. Conversely, the depletion of encephalic noradrenaline following reserpine, as well as the reserpine brain concentration, were not affected by subcutaneously administered calcium chloride, when reserpine was administered either intravenously, or subcutaneously in a site different from that selected for pretreatment with the calcium salt. In essence calcium chloride, a well known irritant, acts accordingly at the site of subcutaneous administration, thus limiting by a non specific mechanism the absorption of reserpine. Under similar conditions, in fact, the absorption of a different drug, i.e. harmaline, was likewise altered. In view of these findings the significance of some studies on calcium-reserpine interaction appearing in the literature requires a reappraisal.

Animals↗
PubMed1982

Calcium-induced spongiform and necrotizing myelopathy.

Selective axonal calcification has been consistently observed in experimental spinal cord trauma in laboratory animals as well as in human spinal cord injury. A hypothesis of calcium influx resulting in activation of proteolytic and/or lipolytic enzymes has been proposed as a major mechanism of nerve fiber degeneration. The current study was undertaken to determine the effects of calcium influx into nontraumatized spinal cord tissue, utilizing 10 per cent calcium chloride at a pH of 7.4 slowly dripped onto the dorsal surface of the surgically exposed spinal cord of adult male Sprague-Dawley rats. Controls consisted of animals similarly treated with solutions of sodium chloride, magnesium chloride, and potassium chloride at the same pH and osmolarity. Sham-operated and normal animals were also observed. The experimental animals that received calcium chloride consistently developed paraplegia that was evident within 24 hours after treatment. The initial spinal cord lesion consisted of discrete areas of spongiosis in posterior and lateral columns in the segment beneath the application of calcium. The spongiosis progressed in severity and was accompanied or followed by necrosis. The gray matter was relatively spared; however, the posterior horns became consistently necrotic. Calcium was observed histochemically in the areas of spongiosis/necrosis but not in spared areas. Although the topography of the calcium-induced myelopathy differs from that of spinal cord injury, the progression of the clinical and pathologic changes is consistent with the calcium-mediated hypothesis of necrosis in the latter.

Animals↗
PubMed1977

Eelvated postoperative renal clearance of amylase without pancreatitis after cardiopulmonary bypass.

Two postoperative cardiopulmonary bypass patients who had pancreatitis within a two week period provided the impetus for pursuing this study. Amylase-creatinine clearance ratios (ACCR) were measured in a series of ten thoracic surgery patients: six coronary artery bypass patients with cardiopulmonary bypass (cardiac group), and four exploratory thoracotomy patients (pulmonary group). These ratios were obtained in the preoperative, recovery room, and postoperative periods. Comparisons were made among the following data: clinical history, pre- and postoperative medications, intraoperative vital signs, drugs, and anesthetics. The preoperative mean ACCR was 3.34 per cent. All cardiac patients had a significantly elevated ACCR in the recovery room with a mean of 17.36 per cent (p less than 0.05). The ACCR had returned to preoperative levels by the second postoperative day in five of six cases. There were no elevated ACCR levels in the pulmonary group. All patients were asymptomatic for pancreatitis. The intraoperative course of the cardiac patients involved four common factors, besides cardiopulmonary bypass, which were not present in the pulmonary group. These similarities included transfusion of citrated fresh whole blood activated by calcium chloride, hypotension treated with ephedrine, administration of mannitol, and intraoperative morphine analgesia. The mechanisms of increased amylase secretion by calcium chloride or ephedrine administration and transient sphincter of Oddi constriction by morphine or the alpha-adrenergic response of ephedrine are considered with the theoretical implications toward pancreatitis. The background and significance of the ACCR are also analyzed, especially in association with the osmotic diuresis of mannitol and a subsequent low urine creatinine level.

Aged↗
PubMed1993

Solubility of calcium salts and carrageenan used in infant formulas did not influence calcium absorption in rats.

Calcium absorption from tricalcium phosphate (TCP) was compared to that from calcium chloride, CaCl2, in the presence and absence of carrageenan in the rat model. There was no difference in percent calcium absorption as indicated by femur uptake of TCP or CaCl2 intrinsically labeled with 45Ca given by gavage (78.4 +/- 9.6 vs. 80.0 +/- 5.9, respectively). Thus, the difference in solubility of the two salts did not influence calcium absorption. When TCP was delivered by gavage in a solution containing 1% carrageenan, calcium absorption was not decreased compared to that of a control without carrageenan. In this model, calcium from TCP in the presence of up to 1% carrageenan is well absorbed.

Animals↗
PubMed2005

Influence of short-term venous stasis on clinical chemistry testing.

Control and standardization of preanalytical variability is a critical factor for achieving accuracy and precision in laboratory testing. Although venous stasis from tourniquet placement during venepuncture should be minimized, as it has been claimed to account for spurious and significant variations for several analytes in plasma, there is controversy surrounding its real impact on laboratory testing. The aim of the present study was the investigation of the influence of short-term venous stasis on routine biochemical testing, by measuring the plasma concentration of 12 common analytes, including proteins, protein-bound substances, enzymes and electrolytes, in plasma specimens collected either without venous stasis or following the application of standardized external pressure of 60 mm Hg using a sphygmomanometer for 1 and 3 min. Although the overall correlation between measures was acceptable, the pattern of change was mostly dependent on the length of stasis, size and protein-binding characteristics of the analytes, achieving clinical significance for albumin, calcium and potassium after 1-min stasis, and alanine aminotransferase, albumin, calcium, chloride, total cholesterol, glucose and potassium after 3-min stasis. Statistically significant differences could be observed in seven (alanine aminotransferase, albumin, calcium, total cholesterol, creatine kinase, iron and potassium) and ten (alanine aminotransferase, albumin, calcium, chloride, total cholesterol, creatine kinase, creatinine, glucose, iron and potassium) out of the 12 analytes tested, after 1- and 3-min venous stasis, respectively. The most clinically significant changes from standard venepuncture, when compared to the current analytical quality specifications for desirable bias, occurred for potassium (1-min stasis, -2.8%; 3-min stasis, -4.8%, both p<0.001), calcium (1-min stasis, +1.6%, p<0.05; 3-min stasis, +3.6%, p<0.001) and albumin (1-min stasis, +3.5%; 3-min stasis, +8.6%, both p<0.001). As most of these effects are dependent on the stasis time during venepuncture and biochemical or physiological characteristics of the analyte, these variations could likely be anticipated, allowing the most appropriate preventive measures to be adopted.

Adult↗