Complete amino acid sequence of tenebrosin-C, a cardiac stimulatory and haemolytic protein from the sea anemone Actinia tenebrosa

The complete amino acid sequence of the cardiac stimulatory and haemolytic protein tenebrosin-C, from the Australian sea anemone Actinia tenebrosa, has been determined by Edman degradation of the intact molecule and fragments produced by treatment of the polypeptide chain with cyanogen bromide and enzymatic cleavage with endoproteinase Asp-N, thermolysin and trypsin. The molecule is a single-chain polypeptide consisting of 179 amino acid residues with a calculated molecular mass of 19,797 Da. Tenebrosin-C shows a high degree of amino acid sequence similarity (63%) with Stoichactis helianthus cytolysin III [Blumenthal, K. M. and Kem, W. R. (1983) J. Biol. Chem. 258, 5574-5581] and is identical to a partial sequence (90 residues) reported for equinatoxin, a cardiostimulatory and haemolytic protein isolated from the European sea anemone Actinia equina [Ferlan, I. and Jackson, K. (1983) Toxicon Suppl. 3, 141-144]. No amino acid sequence similarity was detected between tenebrosin-C and other protein sequences stored in available databases. The predicted secondary structure of tenebrosin-C suggests that it is a compact, highly structured molecule.

Buffer agents do not reverse intramyocardial acidosis during cardiac resuscitation

We investigated the effects of carbon dioxide-producing and carbon dioxide-consuming buffers on intramyocardial pH and on cardiac resuscitability. In 29 pigs, intramyocardial pH was continuously measured with a glass electrode advanced into the midmyocardium of the posterior left ventricle through a diaphragmatic window. Ventricular fibrillation (VF) was electrically induced by alternating current applied to the epicardium of the left ventricle. After 3 minutes of VF, precordial compression was begun and continued for an interval of 8 minutes. Sodium bicarbonate (a carbon dioxide-generating buffer), Carbicarb (a carbon dioxide-consuming buffer), and hypertonic sodium chloride (control solution) were infused into the right atrium during cardiac resuscitation. Defibrillation was attempted by transthoracic direct-current shock after 11 minutes of VF. Intramyocardial pH progressively decreased from an average value of 7.26 before VF to 6.87 before infusion of buffers. Systemic circulation and great cardiac vein pH significantly increased after administration of the two buffer agents. However, intramyocardial pH continued to decline to an average of 6.62 after 11 minutes of VF, and this decline was not altered by either buffer solution or by the saline control. As in previous studies, resuscitability was closely related to coronary perfusion pressure at the time of direct-current countershock but not to pH. Accordingly, the rationale of reversing acidosis by the administration of these buffer agents is not supported. Even more important, neither carbon dioxide-consuming nor carbon dioxide-producing buffers altered myocardial acidosis or improved myocardial resuscitability under controlled experimental conditions of cardiac arrest.

Virus enhances IgE- and non-IgE-dependent histamine release induced by bacteria and other stimulators

Histamine release from human basophil leukocytes was triggered by Staph. aureus, Salmonella enteritidis, non-haemolytic streptococci, or E. coli. Influenza A virus was found to enhance the mediator release and the effect was caused by synergism, since the virus did not induce release of histamine per se. This potentiating effect of the virus was seen both when the bacteria-induced histamine release was IgE-dependent (i.e. patient sensitized to the bacterium) and when the bacterium caused mediator release by a non-immunological mechanism independent of IgE (putative sugar-lectin mediated). Histamine release induced by anti-IgE and calcium ionophore or agarose-beads was also enhanced in the presence of the virus. These findings indicate that influenza A virus potentiates both IgE- and non-IgE-mediated histamine release induced by bacteria and other stimulators.

Cytokine-induced release of histamine from basophil leukocytes from AIDS patients

Cytokine-induced histamine release from basophil leukocytes was examined in cell suspension from AIDS patients and compared with healthy controls. Cells from approximately half of the AIDS patients, in contrast to none from the control group, showed histamine release after stimulation with interleukin-4 (IL-4), tumor necrosis factor alpha (TNF alpha), lymphotoxin (LT) and interferon gamma (IFN gamma). These cytokines seem to induce histamine release from cells from AIDS patients by interaction with the cell surface immunoglobulins, since removal of the immunoglobulins prior to the exposure of the cytokines completely abolished the response to the cytokines. IL-1 alpha, IL-1 beta, IL-3, colony stimulating factor (CSF) and granulocyte-macrophage-CSF (GM-CSF) caused significant histamine release from cells from a similar number of AIDS patients and controls.

Carbohydrates inhibit the potentiating effect of bacteria, endotoxin and virus on basophil histamine release

Histamine release caused by calcium ionophore A23187 and anti-IgE was examined in leukocyte suspensions from 8 healthy individuals. Staphylococcus aureus, lipopolysaccharide (LPS) from Salmonella typhimurium and influenza A virus were found to enhance the histamine release but did not release histamine per se. The potentiation of mediator release depends on a non-transient signal since the potentiating effect was also obtained by preincubation of the cells with LPS followed by wash-out and stimulation of the cells with anti-IgE. The potentiation was abolished or reduced by galactose, N-acetyl-glucosamine, alpha-methyl-D-glucoside, alpha-methyl-D-mannoside, N-acetylneuraminic acid and lactose, but not by glucose. These findings indicate that the enhancement of mediator release by bacteria, endotoxin, and virus depends on a sugar-mediated reaction.

Haemophilus influenzae potentiates basophil histamine release possibly by its endotoxins

Haemophilus influenzae and its extracellular products (EP) did not release histamine in leukocyte suspensions from normal individuals. However, the EP were found to enhance basophil histamine release triggered by anti-IgE and by the calcium ionophore A23187. Experiments with EP indicate that it is the content of endotoxins which is responsible for the potentiating effect. Removal of endotoxin from the EP thus completely abolished the potentiating effect, whereas inactivation of its protease and proteins by heat-treatment or by proteinase K did not change the potentiation. A reinforcement of mediator release by the extracellular products of H. influenzae might play a pathophysiological role in chronic obstructive pulmonary disease.

Hemolysins: pore-forming proteins in invertebrates

Invertebrates possess lytic molecules which lyse vertebrate erythrocytes. In all the species studied so far, hemolytic activity depends on proteins which possess a wide range of reactivity. It is generally calcium-dependent and heat-labile, although calcium-independent and heat-stable hemolysins have also been detected. The molecules interact with sugars or lipids which could represent the membrane receptors by which circular lesions on target membranes are produced. On the basis of some analogies with vertebrate lytic molecules it is conceivable that the hemolysins evolved from a common ancestral gene which also led to vertebrate pore-forming proteins.

Cardiac effects of carbon dioxide-consuming and carbon dioxide-generating buffers during cardiopulmonary resuscitation

Recent studies have demonstrated an increase in carbon dioxide (CO2) tension (PCO2) in both mixed venous and coronary vein blood early in the course of cardiac arrest and cardiopulmonary resuscitation. Because increased PCO2 in the myocardium correlates with both ischemic injury and depression of contractile function, the effects of hypertonic solutions of either the CO2-"generating" sodium bicarbonate (NaHCO3) buffer, a mixture of sodium carbonate (Na2CO3) and sodium bicarbonate (carbicarb) acting as a CO2-"consuming" buffer, or saline placebo (NaCl) were compared during cardiopulmonary resuscitation in 25 healthy minipigs. Both buffer agents significantly increased the pH and HCO3- of arterial, mixed venous and coronary vein blood. Bicarbonate increased whereas carbicarb reduced blood PCO2 in the systemic circuit as anticipated. However, neither the PCO2 nor the lactate content of coronary vein blood was favorably altered by buffer therapy. Four of eight animals treated with bicarbonate, five of eight treated with carbicarb and six of nine placebo-treated animals were successfully resuscitated and had a comparable 24 h survival rate. Coronary perfusion pressure during precordial compression, a critical determinant of resuscitability, was transiently decreased by each of the hypertonic solutions. Accordingly, neither CO2-generating nor CO2-consuming buffers mitigated increases in coronary vein PCO2 or improved the outcome of cardiopulmonary resuscitation under these experimental conditions.

Regulation of intracellular pH in the myocardium; relevance to pathology

Intracellular pH affects the contractile function of the heart, metabolic reactions, ion exchange and calcium homoeostasis. Numerous studies have concluded that a fall of extracellular pH, by whatever mechanism, causes a fall of contractility by alteration of intracellular pH. Measurement of cytosolic intracellular pH using microelectrodes has confirmed that earlier deduction. Acidosis reduces the slow calcium current and the release of calcium from the sarcoplasmic reticumul but, because the cytosolic calcium does not fall, the major site of action of hydrogen ions appears to be on the calcium sensitivity of the contractile proteins. In man acidosis can be detected 15 s after the occlusion of a coronary artery and is a major mechanism for the simultaneous loss of contractility in ischaemia. A transient alkalosis is not detected in man but has been reported in isolated heart preparations where ATP consumption is low. An imposed mild respiratory acidosis during hypoxia increases the subsequent recovery of mechanical function on reoxygenation whereas a severe acidosis can be harmful. Acidosis in ischaemic may be advantageous due to a cardioplegic effect, inhibition of transsarcolemmal calcium fluxes or a reduction of mitochondrial calcium overload. Calcium uptake on reperfusion or reoxygenation has been linked to an inward movement of sodium in exchange for hydrogen ions on reperfusion and subsequent sodium-calcium exchange. Such a mechanism in its simplest form cannot account for the similar uptake of calcium on reoxygenation and reperfusion. Acidosis is a cause of early contractile failure in ischaemia but the role of acidosis in causing cell necrosis is not established.

Myocardial acidosis associated with CO2 production during cardiac arrest and resuscitation

Previous studies from our institution demonstrated significant hypercarbic acidosis in the mixed venous (pulmonary artery) blood in animals and human patients during cardiac arrest and cardiopulmonary resuscitation (CPR). In the present study, the acid-base state of the myocardium during cardiac arrest was investigated. Cardiac arrest was electrically induced in 11 pentobarbital-anesthetized and mechanically ventilated domestic pigs. Precordial compression was begun 3 minutes after onset of ventricular fibrillation and continued for 8 minutes. During CPR, there was rapid onset of profound myocardial acidosis with an increase in intramyocardial [H+] from 54 +/- 5 to 146 +/- 20 nmol/l (7.27 +/- 0.04 to 6.88 +/- 0.20 pH units). Great cardiac vein PCO2 increased from 57 +/- 2 to 158 +/- 12 mm Hg. Profound hypercarbic acidosis in great cardiac vein blood was associated with myocardial lactate production to levels of 8.1 +/- 0.7 mmol/l. Only moderate decreases in cardiac vein bicarbonate concentrations from 31 +/- 1 to 23 +/- 1 mmol/l were observed. These acid-base changes were almost completely reversed over an interval of 60 minutes after the animals were successfully resuscitated by DC countershock. The PCO2 in cardiac vein blood was significantly greater than that of mixed venous blood, demonstrating disproportionate myocardial production of CO2 during CPR. Accordingly, it is CO2 production during ischemia that is implicated as the predominant mechanism accounting for myocardial [H+] increases during cardiac arrest. Important clinical implications for buffer therapy during CPR and, in particular, treatment with bicarbonate emerge from these observations.

Electrical and mechanical responses to inhibition of cell respiration in vascular smooth muscle of the rat portal vein

Metabolic regulation of contractility in vascular smooth muscle was studied in the spontaneously active rat portal vein using respiratory depression by cyanide (0.2-2.0 mM) as a model for tissue hypoxia. Intracellular recordings of electrical activity were done with concomitant registration of force development. Average membrane potential in the absence of cyanide was -61 +/- 1 mV (n = 27). Addition of cyanide to normal Krebs solution resulted in a reduction of force amplitude and the number of action potentials per burst, with a relatively more pronounced effect on the mechanical activity. At moderate levels of inhibition of force amplitude the frequency of spontaneous bursts of action potentials transiently increased concomitant with a slight depolarization, but after prolonged (15-20 min) exposure to cyanide the membrane repolarized to the level prior to cyanide addition and the burst frequency decreased to be equal to or lower than that in the absence of cyanide. Higher concentrations of cyanide totally inhibited spontaneous mechanical and electrical activity. In contrast to the results with glucose, it was found that when beta-hydroxybutyrate was used as substrate the addition of 2 mM cyanide led to a marked hyperpolarization (13 +/- 1 mV) after total inhibition of spontaneous activity. The hyperpolarization was not prevented by administration of 4-aminopyridine (2.5 mM) or tetraethylammonium (4-6 mM) prior to the addition of cyanide. To investigate the effects of increased metabolic demand on the relation between force and membrane potential in cyanide-treated muscle, high-K+ (40 mM) contractures were studied. Contractures were associated with depolarization of 34 +/- 3 mV (n = 5). 1 mM cyanide reduced the amplitude of the contractures to about 9% of control with a moderate reduction in the amount of depolarization (28 +/- 1 mV, n = 5). It is concluded that the decrease of mechanical activity during respiratory inhibition may partly reflect a reduction in the number of spikes per burst but that other mechanisms, independent of membrane activity, also contribute to the inhibition. The increase of glycolysis during respiratory inhibition seems to prevent more pronounced changes in membrane potential.

In vitro buffering capacity of cardiac and skeletal muscle tissue in normotensive and hypertensive rats. Assessment using PCO2 equilibration of homogenates

Experiments were performed to assess the in vitro buffering capacity (physicochemical buffering) of cardiac and skeletal muscle tissue in normotensive and hypertensive rats using the techniques of PCO2 equilibration of tissue homogenates. We have previously shown (Oldershaw PJ, Cameron IR. Int J Cardiol 1988;18:131-141 and Int J Cardiol 1988;18:143-149) that the ability of myocardial cells to regulate intracellular pH is improved in association with left ventricular hypertrophy (induced by experimental hypertension) and this study purports to investigate the role of physicochemical buffering in this improved control. Rats were made hypertensive using the technique of sub-diaphragmatic aortic constriction and left for 1 or 4 weeks at which time samples of left ventricular and skeletal muscle tissue were taken for analysis; sham-operated animals were used as controls. The tissue was homogenised and in vitro buffering capacity assessed using PCO2 equilibration. The slope of the log PCO2-pH plot was calculated for each tissue and taken as a measure of buffering capacity. In control animals, in vitro buffering was greater in skeletal than cardiac muscle (slopes 1.89 +/- 0.5 cf. 1.64 +/- 0.06 P less than 0.05). In association with hypertension of 1 or 4 weeks duration the buffering capacity of left ventricular tissue increased to 2.00 +/- 0.08 (P less than 0.01) at 1 week and to 2.05 +/- 0.06 (P less than 0.01) at 4 weeks. There was no comparable change in the buffering capacity of skeletal muscle tissue. At least part of the observed in vivo changes in intracellular pH control may therefore be explicable on the basis of improved intracellular physicochemical buffering.

HIV antigen stimulates basophil leukocytes from AIDS patients to release histamine due to type I allergy

HIV antigen-induced histamine release was examined in leukocyte suspensions from 12 patients with AIDS and 10 healthy controls. Nine of the twelve patients released histamine, while no release was obtained in cells from the control group. The mechanism was examined by removal of immunoglobulins (Ig) from the patient cells before stimulation with HIV antigen, which resulted in an abolition of the histamine release. Transfer of the Ig to cells from normal individuals rendered these cells able to respond to HIV. The removal and fixation of Ig were followed by disappearance and reappearance of the response to anti-IgE. These findings indicate that the histamine release by HIV is caused by a type I (IgE-mediated) reaction.

Effect of amiloride on arachidonic acid and histamine release from rat mast cells

The effect of a putative Na+/H+ exchange inhibition on histamine and [14C]arachidonic acid ([14C]AA) release has been examined in rat peritoneal mast cells, using either addition of amiloride or removal of extracellular Na+. The cells were stimulated by non-immunological agents, i.e. calcium ionophore A23187, nerve growth factor (NGF), thapsigargin and compound 48/80. On the basis of the results obtained, a possible role for Na+/H+ exchange in rat mast cell secretion is discussed.

Influenza A virus enhances IgE-mediated histamine release from human basophil leukocytes. Examination of the effect of viral neuraminidase and haemagglutinin

Histamine release caused by anti-IgE was examined in leukocyte suspensions from 10 healthy individuals. Influenza A virus was found to enhance the histamine release but did not release histamine per se. When monoclonal antibodies directed against the viral neuraminidase were included in the samples, the potentiating effect of the virus was completely abolished. The same occurred using a neuraminidase inhibitor. However, monoclonal antibodies directed against the viral haemagglutinin also abolished the potentiation. A binding of virus to the basophil cell surface by haemagglutinin therefore seems to be necessary for the viral neuraminidase to cause potentiation of mediator release.

Influenza A virus enhances allergic histamine release. Effect of neuraminidase

Histamine release was examined in leukocyte suspensions from patients allergic to house dust mite, grass pollen, birch pollen or cat dander. Influenza A virus was found to enhance the antigen-induced mediator release, but did not cause release of histamine from the cells per se. Also histamine release induced by anti-IgE in cell suspensions from normal individuals was enhanced by virus. The potentiating effect of influenza A virus might be due to neuraminidase on the surface of virus, since a similar effect was caused by a purified neuraminidase obtained from Vibrio cholerae, and the effect of virus as well as the neuraminidase was completely abolished by a potent neuraminidase inhibitor. The synergistic enhancement in IgE-mediated histamine release by virus could be of significance for the conversion from latent to manifest asthma.

Influenza A virus enhances Staphylococcus aureus-induced basophil histamine release in normal individuals and patients with intrinsic asthma

Influenza A virus was found to enhance Staphylococcus aureus-induced histamine release in human leukocyte suspensions, but did not per se release histamine. This potentiating effect was found to be similar in cells from normal individuals and from patients with intrinsic asthma. The enhancement of mediator release could be due to viral neuraminidase on the surface of the virus, since a similar potentiating effect was caused by a purified neuraminidase preparation obtained from Vibrio cholerae, and the effect of virus as well as of the purified neuraminidase was completely abolished by a potent neuraminidase inhibitor. The potentiating effect of virus on bacteria-induced mediator release might be of importance for the conversion from latent to manifest asthma in upper respiratory tract infections.

Inhibition by amiloride and by Na+-depletion of A23187-stimulated arachidonic acid and histamine release from rat mast cells

Rat peritoneal mast cells, labelled with [14C]arachidonic acid, released histamine and [14C]arachidonic acid upon the addition of A23187. The release induced by low concentrations of A23187 was suppressed by removal of extracellular Na+ and by addition of the Na+/H+ exchange inhibitor, amiloride. Addition of protein kinase C inhibitors resulted in only a modest decrease of [14C]arachidonic acid and histamine release. [14C]Arachidonic acid was hydrolyzed from both phosphatidylcholine and triacylglycerol. Amiloride inhibited only the hydrolysis from phosphatidylcholine. It is suggested that an Na+/H+ exchange is stimulated secondary to an A23187-induced increase in intracellular calcium concentration. Increased Na+/H+ exchange seems to facilitate the activation by intracellular calcium ions of phospholipase A2 as well as of histamine secretion.

A new immunotoxin built by linking a hemolytic toxin to a monoclonal antibody specific for immature T lymphocytes

Hybrid molecules built by conjugation between monoclonal antibodies (MAbs) and toxins are currently being experimentally tested as potential new anti-cancer agents. These immunotoxins have mainly used the plant toxin ricin as the toxic component, which inhibits protein synthesis at the ribosome level. We present an alternative for toxic components using a hemolytic toxin acting at the membrane level, due to its phospholipase activity. The hemolytic toxin (HT), isolated from the sea anemone Stoichactis helianthus, has been conjugated to an antibody towards an antigen expressed on immature T lymphocytes (IOR-T6), by means of an artificial disulphide bridge. The hybrid IOR-T6-HT exhibits no hemolytic activity unless it is reduced. It is toxic for cells (CEM) expressing the IOR-T6 antigen and non-toxic for cells (K562) not bearing the antigen. An excess of unconjugated antibody reverses the toxicity. Immunotoxins based on membrane-active, hemolytic toxins can be a useful alternative when directed towards antigens which do not mediate internalization, as is the case for most carcinoma antigens.

Effects of tromethamine and sodium bicarbonate buffers during cardiac resuscitation

The effects on cardiac resuscitability of iso-osmolal solutions of tris-hydroxymethyl-aminomethane (tromethamine), sodium bicarbonate (NaHCO3) and sodium chloride placebo were compared in 30 domestic pigs using a well-established model of electrically induced cardiac arrest and resuscitation. We hypothesized that a carbon dioxide (CO2) consuming buffer like tromethamine would reduce and sodium bicarbonate would increase the respiratory acidosis of mixed venous blood, which had recently been demonstrated in our laboratory, Tromethamine did decrease and sodium bicarbonate did increase both arterial and mixed venous CO2 during cardiopulmonary resuscitation (CPR). Both concentrations of end-tidal CO2 and coronary venous PCO2 were significantly lower after tromethamine than after bicarbonate. However, tromethamine produced an unexpected vasodilator effect with reduction of mean aortic and coronary perfusion pressures to levels that are known to reduce resuscitability and survival independently of its buffer action. Neither resuscitability nor survival was altered by bicarbonate therapy in comparison with sodium chloride placebo.

Virus enhances histamine release from human basophils

Histamine release from human basophil leukocytes was triggered by Staph. aureus or by complement activation caused by endotoxins isolated from E. coli or Salmonella bacteria. Influenza A virus was found to enhance the mediator release and the effect was caused by synergism, since the virus itself did not release histamine. The potentiating effect of the virus was abolished by a potent neuraminidase inhibitor. Furthermore, a purified neuraminidase preparation obtained from Vibrio cholerae caused a similar potentiating effect, which was also abolished by the neuraminidase inhibitor. These findings indicate that the neuraminidase on the surface of influenza A virus is responsible for the potentiating effect of the virus on basophil histamine release.

Basophil histamine release in insect venom allergy

The aim of the present study was to investigate venom-related and venom-non-related immunological reactions in patients stung by bee or wasp. Sixteen consecutive patients (7 with local and 9 with systemic reactions) were tested with skin tests, RAST and basophil histamine release (BHR) test immediately after the insect sting and 2, 4, and 16 weeks later. No test was useful immediately after the insect sting, the "anergic period". In agreement with earlier findings, the SPT was the only allergy test that showed statistically significant differences between patients with local and systemic reactions, although a great overlap was found. Release of histamine from basophils after incubation with anti-IgE also showed statistically significant differences between local and systemic reactions. Further studies are needed, especially measurement of BHR after incubation with anti-IgE before insect stings.

Influenza A virus potentiates basophil histamine release caused by endotoxin-induced complement activation. Examination of normal individuals and patients with intrinsic asthma

Histamine release from human basophil leukocytes was triggered by complement activation by means of endotoxins isolated from E. coli and Salmonella bacteria. Influenza A virus was found to enhance the mediator release, and the effect was caused by synergism, since virus itself did not release histamine. The potentiating effect was similar in cells from normal individuals and from patients with intrinsic asthma. The involvement of viral neuraminidase was examined by a potent neuraminidase inhibitor and this inhibitor completely abolished the potentiating effect by virus. A purified neuraminidase preparation obtained from Vibrio cholerae caused a similar potentiating effect in mediator release and the effect was abolished by the neuraminidase inhibitor. These findings indicate that viral neuraminidase is responsible for the potentiating effect of virus on the histamine release. This effect might play a role in septic conditions and possibly contribute to asthmatic attacks by infections.

Separation and characterization of four different amino acid sequence variants of a sea anemone (Stichodactyla helianthus) protein cytolysin

A basic protein cytolysin previously isolated from the Caribbean sea anemone Stichodactyla helianthus was shown by CM cellulose chromatography to consist of four isotoxins possessing different N-terminal amino acid sequences. These are designated as toxins I-IV in order of increasing isoelectric point. The estimated molecular sizes (17,400-18,200) of toxins I-III were very similar; toxins I and II posses one additional amino acid at their amino terminus relative to toxin III. Under denaturing conditions, toxin IV behaved as a significantly larger (19,600) polypeptide; Edman sequencing established that it possesses a seven residue extension at the N-terminal end relative to toxin III. None of the variants contained half-cystines or reducing sugars. Toxin III contributed 83% of the total purified cytolytic (hemolytic) activity, toxin II 14%, and the relatively insoluble toxins I and IV together only contributed about 3% of the total cytolytic activity. Cytolysin III lysed Ehrlich ascitic tumour cells, but when administered intraperitoneally in nonlethal doses to mice already inoculated with this tumour, it failed to protect the mice against the tumour. Comparison of the partial amino acid sequence of equinatoxin, another sea anemone protein cytolysin, with that of Stichodactyla cytolysin III indicates they are highly homologous. Many other cytolytic proteins isolated from sea anemones share these properties with Stichodactyla cytolysins: (1) selective inhibition of hemolytic activity by preincubation with sphingomyelin, (2) a molecular size of 10,000-20,000, and (3) an isoelectric point of 9 or above.

Phospholipase D activity of Vibrio damsela cytolysin and its interaction with sheep erythrocytes

Exposure of sheep erythrocytes to sublytic amounts of Vibrio damsela cytolysin markedly reduced their membrane sphingomyelin content and their sensitivity to lysis by the sphingomyelin-dependent cytolysins staphylococcal sphingomyelinase C (beta-toxin) and helianthin. The toxin was found to be a phospholipase D active against sphingomyelin.

Histamine release from basophil leukocytes in asthma patients after in vitro provocation with various neuromuscular blocking drugs and intravenous anaesthetic agents

Basophil histamine release is a relatively new investigation technique, which can be used in the diagnosis of anaphylactoid reactions. Our aim in this investigation was to determine reference values for asthma patients and normal subjects. Blood from eight asthmatic patients and eight normal subjects was tested for histamine release after in vitro provocation with various neuromuscular blocking drugs and intravenous anaesthetic agents. There was significantly higher histamine release for asthmatic patients than for normal subjects, P less than 0.001 (analysis of variance). This had no effect on the calculated reference value (mean +/- 2 s.d.), which was found to be 0-30%.

Comparison of the action of calcium antagonists on basophil histamine release

The inhibitory capacity of calcium antagonists on basophil histamine release was examined in allergic patients and in controls. All dihydropyridines tested (nifedipine, nimodipine, nitrendipine, nicardipine, felodipine) dose-dependently inhibited anti-IgE- and A23187-induced release with an order of potency of felodipine greater than nicardipine greater than nifedipine = nimodipine = nitrendipine. Only the inhibition induced by felodipine and nicardipine on anti-IgE-induced release could be counteracted by increasing extracellular calcium. Diltiazem, not belonging to the dihydropyridines, was a weak inhibitor. A combination of felodipine and verapamil in low concentrations exerted a synergistic inhibitory effect on histamine release, whereas this was not the case with other combinations of antagonists. The results suggest differences in the mode of action of the 1.4-dihydropyridines. This might be of significance in the search for calcium antagonists suitable in the treatment of allergic diseases.

Coronary sinus pH during percutaneous transluminal coronary angioplasty: early development of acidosis during myocardial ischaemia in man

Coronary sinus pH was measured continuously in eight patients undergoing angioplasty to the left anterior descending coronary artery. A catheter tip pH sensitive electrode with a response time of less than 300 ms and an output of greater than or equal to 57 mV/pH unit was placed high in the coronary sinus. Recordings were obtained during a total of 24 balloon occlusions of the left anterior descending coronary artery varying in duration from 5 to 45 s. Continuous 12 lead surface electrocardiograms were recorded. During or after balloon inflation of greater than or equal to 12 s (n = 4) there was no change in coronary sinus pH or the electrocardiogram. During balloon inflation of greater than or equal to 15 s (n = 20) coronary sinus pH was unaltered but between 4 and 6 s after balloon deflation coronary sinus pH fell transiently by between 0.010 and 0.120 pH units before returning to the control value within 65 s. Ischaemic changes were seen on the electrocardiogram during 15 balloon occlusions. In individual patients the peak fall in coronary sinus pH was related to the duration of occlusion of the left anterior descending coronary artery. A rise in coronary sinus pH (alkalosis) was never seen. In man acidosis occurs in the myocardium after short periods (greater than or equal to 12 s) of ischaemia. The fall of pH precedes ischaemic changes on the surface electrocardiogram and occurs concurrently with the earliest reported changes in contractile function.

A new glass microfibre-based histamine analysis for allergy testing in children. Results compared with conventional leukocyte histamine release assay, skin prick test, bronchial provocation test and RAST

A new microfibre method for allergy testing measuring histamine release from human basophil leukocytes is described. Samples of 50 microliter washed blood are challenged with the suspected allergens. Released histamine is bound to microfibres and measured by a spectrofluorometrical method after removal of interfering substances by washing. The microfibre method (HR-MM) was compared to the conventional histamine release assay using the Ficoll-Hypaque gradient method (HR-FH) in 19 allergic children tested with one of three allergens. In addition, a comparison was made between the microfibre method and in vivo provocation tests, i.e. skin prick test (SPT), bronchial provocation test (BPT) and allergen specific serum IgE (RAST). It was found that the same individuals responded with histamine release to the same allergens in both histamine release assays, and the dose-response curves were almost identical. A positive correlation was found between the in vivo and in vitro tests. Thus it is concluded that the new method can provide reproducible, analytically precise (at the nanogram level) histamine release results in pediatric cases where: a positive SPT does not correlate with case history; BPT may be considered too hazardous or inconvenient; confirmation of negative or inconclusive SPT or RAST is needed. In contrast to other histamine release assays it is a convenient diagnostic tool in children since only small amounts of blood are needed and at least 96 tests can be carried out in 2 1/2 h.

Complexity of the influence of gangliosides on histamine release from human basophils and rat mast cells

The influence of exogenous addition of gangliosides on histamine release from human basophils and rat mast cells was examined in vitro. Gangliosides dose-dependently inhibited histamine release, and this inhibition was dependent on the ganglioside sialic acid content, since GT1b, having 3 sialic acid moieties, was more potent than gangliosides with 2 moieties (GD1a and GD1b), which again were more potent inhibitors than GM1 with one moiety. Asialo-GM1 was without effect. In high concentrations the gangliosides potentiated basophil histamine release. The modulation of histamine release was reflected in the sensitivity of the cells to extracellular calcium, since inhibition of the release could be counteracted by increasing the extracellular concentration of calcium.

Histamine release from basophil leukocytes induced by microbial antigen preparations in patients with AIDS

Type I allergy against some common microorganisms was investigated in 14 patients with AIDS and 11 human immunodeficiency virus (HIV) antibody-positive homosexual men, and in a control group consisting of 13 heterosexual men without HIV antibodies. Basophil histamine release technique was used as a sensitive method to detect type I allergy against Candida albicans (CA), Herpes simplex virus type I (HSV-I) and cytomegalovirus (CMV). Of the 14 AIDS patients 11 (78%) showed significant histamine release when stimulated with CA, and HSV-I caused release in 10 (71%), whereas no response was obtained by CMV. In the group of HIV antibody-positive men only one released histamine when stimulated with CA and HSV-I and this patient also had lymphadenopathia. In contrast to these results, no release of histamine was obtained in the control group consisting of 13 heterosexual men. The histamine release caused by CA and HSV-I is mediated by an immunological reaction, since the release was abolished and regained by removal from and refixation to the cell surface of the cell-bound immunoglobulins. These results suggest an involvement of type I allergy as a pathogenetic co-factor in some infections in AIDS, and allergic type I reactions to CA and HSV-I might be an indicator for the presence of manifest AIDS.

Selective venous hypercarbia during human CPR: implications regarding blood flow

Thirty-five patients presenting to the emergency department in cardiopulmonary arrest had simultaneous measurement of central venous (cv) and arterial (a) blood gases during CPR with a pneumatic chest compressor and ventilator. The mean cv, arterial pH, and PCO2 values were markedly different (P less than .001). The mean pH gradient (pHa - pHcv) was .31 +/- .10 units and the mean PCO2 gradient (PcvCO2 - PaCO2) was 60.5 +/- 23.6 torr. This selective venous hypercarbia is probably due to a cardiac output that is inadequate to eliminate the CO2 produced from both residual aerobic metabolism and the buffering of anaerobically produced lactic acid. Central venous blood gases are probably a better reflection of actual tissue environment during prolonged cardiac arrest than are arterial blood gases.

Bacteria and their products peptidoglycan and teichoic acid potentiate antigen-induced histamine release in allergic patients

Histamine release was examined in leukocyte suspensions from patients allergic to grass pollen, mite or cat dander or to bacteria (antigen). When the cells were challenged with specific antigen plus bacteria to which the person was not sensitized, these bacteria were found to potentiate the allergic histamine release. The potentiating effect by bacteria might be due to the bacterial cell wall components, peptidoglycan and teichoic acid, which mimic the effect of bacteria.

The influence of cimetidine and ranitidine on basophil histamine release and bronchial reactivity in asthmatic patients

Anti-IgE induced histamine release from isolated basophils after Cimetidine and Ranitidine administration was evaluated in 22 patients with atopic bronchial asthma. The histamine provocation test after Ranitidine treatment in 10 patients with atopic bronchial asthma and 10 patients with peptic ulcer was also performed. Investigations in vitro revealed that Cimetidine and Ranitidine in low concentrations had an inhibitory effect whereas in concentrations of over 10(-6) M and 10(-4) M, respectively, they enhanced histamine release. Investigations in vivo after administration of Ranitidine showed that it does not cause marked changes in the bronchial reactivity in patients with bronchial asthma and any change in patients with peptic ulcer. These preliminary studies seem to suggest that in patients with atopic bronchial asthma and concomitant peptic ulcer Ranitidine is preferable to Cimetidine in the treatment of digestive tract disorders.

Membrane sialic acid influences basophil histamine release by interfering with calcium dependence

The influence of the cell membrane content of sialic acid on basophil histamine release was examined in vitro in allergic patients and normal controls. Enzymatical removal of sialic acid enhanced histamine release induced by allergen and anti-IgE, whereas an increase in membrane sialic acid content by insertion of sialic acid containing gangliosides into the membrane inhibited the mediator release. The reduction in membrane sialic acid content abolished the inhibitory capacity of the calcium channel antagonist nimodipine, whereas the inhibition produced by verapamil and lanthanum was not affected. This difference, together with the previous finding that alterations in membrane sialic acid content is reflected in the cell sensitivity to extracellular calcium, suggest an interaction between membrane sialic acid and the calcium channels involved in basophil histamine release.

Influence of nimodipine, verapamil and lanthanum on histamine release from human basophils: effect of pretreatment with sialidase

Our previous studies suggest that the membrane content of sialic acid influences histamine release from human basophils by interfering with the transmembraneous calcium fluxes preceding histamine release. In this study we investigated a possible interaction between membrane sialic acid and the calcium channels, using the calcium antagonists nimodipine, verapamil and lanthanum. Anti-IgE-induced histamine release was inhibited by verapamil, nimodipine and lanthanum. When cells were pretreated with sialidase in order to remove sialic acid from the cell membrane, the inhibitory action of nimodipine was abolished, whereas the inhibition by verapamil or lanthanum was unaffected. This difference may be explained by the different mode of action of the calcium channel antagonists, and the results suggest an association between membrane sialic acid and the calcium channel.

Effect of lysophosphatidylserine on immunological histamine release

The effect of lysophosphatidylserine on immunological histamine release has been studied in rat peritoneal mast cells actively sensitized with horse serum and in human basophils challenged with anti-IgE. In contrast to other lysophospholipids, lysophosphatidylserine enhances the immunological histamine release in rat mast cells. The effect shows the kinetics of a saturable process with an apparent Km for lysophosphatidylserine of 0.26 microM. A similar Km value (0.21 microM) is found when measuring the non-immunological histamine release activated by lysophosphatidylserine plus nerve growth factor. A comparison with phosphatidylserine shows that a half-maximal response to lysophosphatidylserine occurs at a concentration 4-times lower. In addition, the magnitude of the response is higher. At variance with rat mast cells, lysophosphatidylserine does not influence the histamine release elicited by immunological and non-immunological stimuli in human basophils. The histamine secretion in these cells is instead affected by a calcium ionophore or tetradecanoylphorbolacetate, a compound producing activation of protein kinase C.

Histamine release induced by bacteria. A new mechanism in asthma?

Bacteria release histamine from human basophil leukocytes and mast cells. The release can be caused by an immunological (IgE-dependent) mechanism, but mostly we found a non-immunological (lectin-mediated) mechanism which indicates that mediator release triggered by bacteria can occur without the person being sensitized to the micro-organism in question. Both bacteria and bacterial products such as endotoxins potentiate basophil histamine release caused by allergens in allergic patients or by bacteria in persons sensitized to the micro-organisms. It is therefore tempting to speculate that bacteria and their products might be of importance for asthma by their capacity to release histamine and to potentiate mediator release.

Staphylococcus aureus alpha-toxin. 2. Reduction of epidermal growth factor receptor affinity in PC12 cells

Staphylococcus aureus alpha-toxin, at sub-cytotoxic concentrations, inhibits both the 125I-labeled epidermal growth factor (EGF) binding and autophosphorylation properties of EGF-receptors in PC12 cells. This inhibition occurred only in intact cells and is probably due to a decrease in the affinity of the receptor for EGF. Streptolysin S and parcelsin could mimic the alpha-toxin effect below cytotoxic concentrations, as measured by a 51Cr release assay. In contrast, other membrane perturbing toxins with different lipid specificity, such as tetanolysin and cobra direct lytic factor, inhibited [125I]EGF binding only at cytotoxic concentrations. Staphylococcal alpha-toxin also stimulated 3-fold the specific binding of a radioactive tumor-promoting phorbol ester (PDBu) to PC12 cells at concentrations similar to those required for the inhibition of [125I]EGF binding. Although the exact mechanism for the inhibition of EGF binding by alpha-toxin has not been established, our results suggest that protein kinase C may be involved in this time-dependent process.

Inhibition of basophil histamine release by gangliosides. Further studies on the significance of cell membrane sialic acid in the histamine release process

Histamine release from human basophils was inhibited by preincubation of the cells with a glucolipid mixture containing sialic acid-containing gangliosides. This was true for histamine release induced by anti-IgE, Concanavalin A and the calcium ionophore A23187, whereas the release induced by S. aureus Wood 46 was not affected. It was demonstrated that the inhibitory capacity of the glucolipid mixture could be attributed to the content of gangliosides, since no inhibition was obtained with cerebrosides or with gangliosides from which sialic acid was removed. Preincubation of the cells with the glucolipid mixture increased the sialic acid content of the cells, and this increase was attributed to an insertion of gangliosides into the cell membrane. The inhibition of histamine release was abolished by increasing the calcium concentration, which substantiates our previous findings that cell membrane sialic acid in basophil leukocytes is involved in the regulation of histamine release, possibly by a modulation of the transmembraneous calcium fluxes preceding histamine release.

Basophil histamine release in cord blood. Regulatory role of IgE

Thirty-two cord blood samples were studied for histamine releasing capability by using a sensitive glass microfibre-based histamine analysis. Histamine was obtained after challenge with anti-IgE in 24 of the 32 samples. However, the net release in cord blood was only 25% of that in adult blood and no relationship was found between histamine release response, total IgE in cord plasma, and a family history of atopic diseases. The low histamine release in cord blood seemed to be associated with the immunological IgE receptor complex activation and not with an immature basic cell function, since the calcium ionophore A23187 which bypasses the receptor complex induced identical histamine release curves in cord and adult blood. Furthermore, when comparing the results of passive sensitization of basophils from new-born and adult persons, the new-born basophils possessed a significant fraction of free IgE receptors, whereas in adults most of the receptors were occupied by IgE.

Arteriovenous carbon dioxide and pH gradients during cardiac arrest

In a porcine preparation of cardiac arrest, we demonstrated that there is a marked paradox of venous acidemia and arterial alkalemia. This paradox is related to decreased clearance of CO2 from the lungs when pulmonary blood flow is critically reduced. Accordingly, increased venous PCO2 rather than metabolic acidosis due to lactic acidosis predominates during the initial 8 min of cardiopulmonary resuscitation. Arterial blood gases fail as indicators of systemic acid-base status and therefore as indicators of tissue acidosis.

Copurification of Leptospira interrogans serovar pomona hemolysin and sphingomyelinase C

The hemolytic and sphingomyelinase C activities of supernatants of cultures of Leptospira interrogans serovar pomona tended to copurify when isoelectric fractionation was carried out. Both activities focused primarily at pH 8.1. Considered in conjunction with other circumstantial evidence, the results led to the conclusion that sphingomyelinase C is responsible for hemolysis.

Intra- and extracellular actions of proton on the calcium current of isolated guinea pig ventricular cells

External or internal application of proton on the calcium current was investigated using the whole-cell patch clamp technique in single ventricular cells of the guinea pig. The effect of acid pHo on the calcium current depended on the strength of the buffer in the internal solution. In the presence of 5 mM HEPES in the pipette, external acidification depressed calcium current with the half maximum inhibition of pHo 5.5. When the intracellular pH was buffered strongly to pH 7.2 by 50 mM HEPES within the pipette solution, half maximum inhibition of the calcium current was shifted to the acidic side markedly. When acid was applied in the patch electrode, calcium current was hardly affected by the pH values down to 6.0 in the pipette solution but was depressed by approximately half on further acidification to pH 4.5. When the Na+-H+ exchange system was blocked by superfusing the cell with either amiloride or Na+-deficient solutions (Tris substituted), calcium current was decreased by half at a pipette pH of around 6.5 and was completely and irreversibly blocked at pHpip 6.0. From the above results, we concluded that the calcium current of the ventricular cell is much more sensitive to intracellular protons than extracellular ones.

Enhancement of histamine release from human basophils pretreated with different sialidases

Histamine release from human basophils was investigated in vitro after removal of cell membrane sialic acid by three different sialidases. Pretreatment of the cells with sialidases from Cl. Perfringens, V. Cholera or Influenza virus A2 enhanced histamine release induced by subsequent stimulation of the cells with anti-IgE or the plant lectin Concanavalin A and caused a shift to the left of the dose-response curve for anti-IgE. The enhanced histamine release was reflected in a increased calcium sensitivity, thus suggesting that cell membrane sialic acid might be involved in the calcium fluxes preceeding histamine release. In higher doses the sialidase from Cl. Perfringens caused the cells to release histamine by itself, whereas the sialidases from V. Cholera and Influenza virus A2 in high doses inhibited the cell response to Concanavalin A.

The releasing action of calcium upon cyclic AMP-dependent meiotic arrest in hamster oocytes

The effect of increasing cytoplasmic calcium on cyclic adenosine monophosphate (cAMP)-dependent meiotic arrest (%GV where GV is germinal vesicle) in hamster oocytes was investigated. The hypotheses tested were that calcium is required for the spontaneous maturation of hamster oocytes, elevation of calcium in the oocyte-cumulus complex can antagonize cAMP-dependent meiotic arrest, and the intraoocyte level of cAMP remains unchanged, but heterologous metabolic coupling decreases, concomitant with calcium-stimulation of germinal vesicle breakdown (GVBD). Levels of cAMP were elevated by culturing cells in the presence of dibutyryl cAMP (dbcAMP), isobutylmethylxanthine (IBMX) or forskolin and intracellular levels of calcium were manipulated by altering the CaCl2 concentration in the medium and/or by utilizing EGTA or A23187. Intracellular cAMP was determined by RIA, functional metabolic coupling was assessed by determination of the fraction of radiolabeled uridine marker transferred from the cumulus mass to the oocyte, and meiotic stage was determined cytogenetically. Compared with the proportion of oocytes that underwent meiotic maturation in control medium containing 1.53 mM CaCl2, that of cumulus-free (denuded) oocytes was unaffected by culture in the absence of added CaCl2, while that of cumulus-enclosed (intact) oocytes was significantly decreased (%GV = 59.5 +/- 4.8 and 4.2 +/- 0.9 in 0 and 1.53 mM CaCl2, respectively, P less than 0.001, where GV is germinal vesicle). EGTA prevented, in a dose-dependent manner, the spontaneous maturation of denuded oocytes that occurred in 0 mM CaCl2 (ID50 = 0.05 mM, where ID50 is the dose of EGTA that inhibited GVBD in 50% cultured oocytes). In contrast, compared with the control, less than 1 mM EGTA failed to increase the %GV of intact oocytes, although 5 mM EGTA significantly increased meiotic arrest. The %GVBD of oocytes cultured in medium containing 0 mM CaCl2 was dose-dependent on A23187 for both intact oocytes (ID50 = 3.0 microM) and for denuded oocytes cultured in the presence of 0.5 mM EGTA (ID50 = 2.7 microM). Elevated extracellular calcium significantly antagonized dbcAMP-maintained meiotic arrest in both types of oocyte and the %GV was significantly correlated with the pH of the medium [(r) = -0.78 and -0.60 for intact and denuded oocytes, respectively, P less than 0.001 in both cases]. Both CaCl2 and A23187 induced dose-dependent antagonistic effects on forskolin-maintained meiotic arrest in intact oocytes but neither antagonism was accompanied by significant dose-dependent decreases in either the intraoocyte content of cAMP or the extent of heterologous metabolic coupling.(ABSTRACT TRUNCATED AT 400 WORDS)