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)

Difference in acid-base state between venous and arterial blood during cardiopulmonary resuscitation

We investigated the acid-base condition of arterial and mixed venous blood during cardiopulmonary resuscitation in 16 critically ill patients who had arterial and pulmonary arterial catheters in place at the time of cardiac arrest. During cardiopulmonary resuscitation, the arterial blood pH averaged 7.41, whereas the average mixed venous blood pH was 7.15 (P less than 0.001). The mean arterial partial pressure of carbon dioxide (PCO2) was 32 mm Hg, whereas the mixed venous PCO2 was 74 mm Hg (P less than 0.001). In a subgroup of 13 patients in whom blood gases were measured before, as well as during, cardiac arrest, arterial pH, PCO2, and bicarbonate were not significantly changed during arrest. However, mixed venous blood demonstrated striking decreases in pH (P less than 0.001) and increases in PCO2 (P less than 0.004). We conclude that mixed venous blood most accurately reflects the acid-base state during cardiopulmonary resuscitation, especially the rapid increase in PCO2. Arterial blood does not reflect the marked reduction in mixed venous (and therefore tissue) pH, and thus arterial blood gases may fail as appropriate guides for acid-base management in this emergency.

Cardiac cell action potential duration is dependent upon induced changes in free Ca2+ activity during pH changes in vitro

We examined how changes in solution pH alter myocardial cell action potentials (AP) with and without changes in free [Ca2+] caused by pH induced effects on calcium binding. Guinea pig ventricular tissue was isolated, superfused either with Krebs-Ringer (K-R) bicarbonate, phosphate buffered solution, or with Hepes buffered solution, and electrically paced during control (5% CO2 in O2), acidic (12% CO2), and alkalotic (0% CO2) conditions. Action potentials were recorded with intracellular microelectrodes. Extracellular free [Ca2+] was measured with a calcium ion selective electrode and total soluble calcium was measured by ultrafiltration and spectrophotometry. With a total [CaCl2] of 2.5 mM in the K-R solution, we found a free [Ca2+] of 2.14 mM at pH 7.44 (control), 2.48 mM at pH 6.97 and 1.60 mM at pH 8.19; total soluble calcium concentration was 2.00 mM at pH 8.19. In the Hepes solution, free [Ca2+] was only slightly altered (2.42 to 2.55 mM) within this pH range. Equivalent acidosis of either K-R or Hepes suffusate significantly, and similarly, prolonged the AP and its refractory period. Alkalosis of the Hepes suffusate shortened the AP; but equivalent alkalosis of the K-R suffusate prolonged the AP as did a reduction of [CaCl2] in Hepes suffusate from 3.0 to 1.5 mM at pH 7.43. Our study demonstrates that a paradoxical increase in APD occurs because free Ca2+ ion activity falls in K-R solution and overrides the effect of alkalosis alone to decrease APD.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunologic histamine release from isolated human basophils during specific immunotherapy

Anti-IgE- and antigen-induced histamine release from basophils isolated from 20 atopic patients sensitive to grass pollen allergens was evaluated. The studies were made before and after short-term immunotherapy with Pollinex. It was shown, that after hyposensitization a significant decrease on anti-IgE and specific antigen-induced histamine release from basophils occurs.

Bronchial hyper-reactivity in atopic patients during H2-receptor blocker treatment

Bronchial reactivity after Cimetidine treatment was evaluated by the histamine provocation test in 24 patients with atopic bronchial asthma and 10 patients with peptic ulcer. Anti-IgE induced histamine release from isolated basophils was also investigated. After blockade of H2 receptors, an increase of bronchial reactivity and an exacerbation of clinical symptoms were observed in 4 asthmatic patients [17%]. A moderate increase in bronchial reactivity without exacerbation of asthma symptoms was observed in 16 other patients [66%]. In some of the patients treated with Cimetidine an enhancement of IgE-induced histamine release from isolated basophils was observed.

Endotoxins release histamine by complement activation and potentiate bacteria-induced histamine release

The histamine-releasing capability of bacterial lipopolysaccharides (LPS) was examined in human leukocyte suspensions. LPS alone did not release histamine, but it was found to enhance the histamine release caused by bacteria in basophils from persons sensitized to these bacteria. In the presence of serum, LPS was able to release histamine through complement activation. It is speculated that endotoxins reinforce release of histamine caused by bacteria in persons sensitized to these microorganisms, and a direct mediator release via complement activation might play a role in septic conditions.

Influence of bacterial endotoxins on basophil histamine release. Potentiation of antigen- and bacteria-induced histamine release

The histamine-releasing capability of lipopolysaccharides (LPS) was examined in human leukocyte suspensions. LPS alone did not release histamine, but was found to enhance the histamine release caused by anti-IgE. Also the IgE-mediated histamine release caused by specific antigens (allergens or bacteria) in sensitized individuals was enhanced by LPS. The potentiating effect of LPS was observed in grass pollen and dog dander allergic patients as well as in patients sensitized to E. coli or Staph. aureus bacteria. No potentiation was obtained by exposure to unspecific allergens or bacteria to which the persons were not sensitized. Bacteria can release histamine by immunological or nonimmunological mechanisms, and only the immunological histamine release was found to be potentiated by LPS. It is speculated that endotoxins reinforce release of histamine caused by allergens in allergic patients or by bacteria in persons sensitized to these microorganisms.

Influence of neuraminidase and N-acetylneuraminic acid on basophil histamine release in vitro

Since N-acetylneuraminic acid (NANA) in cell membrane glucocalyx mediates or modulates a variety of actions, such as mediator release, we examined a possible modulating role of this amino sugar in histamine release from human basophil leukocytes. Removal of NANA from the cell membrane by the enzyme neuraminidase caused a dose-dependent histamine release. Removal of smaller amounts of NANA enhanced histamine release induced by anti-IgE, Concanavalin A and the calcium ionophore A23187, and reduced the interval between addition of antigen and initiation of histamine release. Pretreatment with free NANA had the opposite effects, i.e. a diminished and delayed maximal histamine release. The hypothesis that NANA in the cell membrane modulates the cellular response to stimulation was further substantiated by demonstrating that the altered response was reflected by a change in the sensitivity of the cell to extracellular calcium. NANA in the cell membrane glucocalyx thus seems to modulate the basophil response to stimulation by modulating transmembraneous calcium transport.

Na+-H+ exchange in cardiac sarcolemmal vesicles

The transport of Na+ by a purified sarcolemmal vesicular preparation from canine ventricular tissue was studied as a function of both internal and external pH. The uptake of Na+ into sarcolemmal vesicles increased upon raising the extravesicular pH of the reaction medium. Half-maximal uptake of Na+ was observed at a pHo of about 8.1 and maximal uptake occurred at pH 8.6. The uptake of Na+ by sarcolemma was also dependent upon the intravesicular pH. Na+ uptake into sarcolemmal vesicles was greatly attenuated in the absence of a H+ gradient across the membrane. Transport of Na+ was potently inhibited by amiloride, a known blocker of Na+-H+ exchange. LiCl was also an effective inhibitor of Na+ transport. In the presence of optimal H+ gradients, Na+ uptake was linear for the first 5 seconds of the reaction and exhibited a Vmax of 290 nmol Na+/mg per min and a KNa of 3.5 mM. These experiments strongly indicate the presence of a Na+-H+ exchange system in cardiac sarcolemma. This activity appeared to be relatively specific for this membrane fraction. The identification of Na+-H+ exchange activity in a sarcolemmal vesicular fraction from the heart will permit extensive characterization of the regulation and kinetics of this antiporter in future investigations.

Comparative toxinology of Loxosceles reclusa and Corynebacterium pseudotuberculosis

In contrast to other kinds of phospholipases, phospholipases D that are toxic for humans and animals are not commonly encountered as constituents of venoms or as products of pathogenic microorganisms. Toxic phospholipases D are present, however, in the venom of the brown recluse spider (Loxosceles reclusa) and in supernatants or filtrates of cultures of Corynebacterium pseudotuberculosis. Although the two enzyme toxins are derived from phylogenetically disparate entities, they are similar in molecular weight, charge, substrate specificity, and in several biological activities. They are immunologically distinguishable.

Basophil histamine release in asthma patients after in vitro provocation with Althesin and etomidate

Our aim was to compare the histamine-releasing effect of etomidate and Althesin on basophil leukocytes from asthmatic patients and normal persons. Blood from eight asthmatic patients and six normal persons was tested for histamine release after in vitro provocation with etomidate and althesin. In the group of asthmatic patients there was a significantly higher histamine release after provocation with althesin than after provocation with etomidate at all concentrations (P less than 0.05, P less than 0.01, P less than 0.02). There was significantly higher histamine release for asthmatic patients than for normal persons after provocation with althesin at all concentrations (P less than 0.05, P less than 0.01, P less than 0.02). There was no difference between the asthma group and the normal group after provocation with etomidate. Data were analysed using Wilcoxon's and Mann-Whitney's rank sum tests. We conclude that asthmatic patients may risk bronchospasm during induction of anaesthesia with althesin, and that etomidate may be suitable intravenous anaesthetic for asthmatic patients.

Sensitive glass microfibre-based histamine analysis for allergy testing in washed blood cells. Results compared with conventional leukocyte histamine release assay

The new microfibre method for allergy testing is based on basophil histamine release after challenge with suspected allergens in samples of 50 microliter washed blood cells. Released histamine is bound to microfibres and measured after removal of interfering substances by washing. The microfibre method was compared with the conventional leukocyte histamine release assay in 18 allergic patients tested with 10 different allergens. It was found that the same individuals responded with histamine release to the same allergens in both assays, and the number of responders was almost identical. Also the dose-response curves and the cell sensitivity were almost identical, which further substantiated identity between the results obtained by the new microfibre method and the conventional assay. A comparison between the microfibre method and in vivo provocation tests showed good agreement when comparing the number of positive and negative responses in these test. The new method overcomes the problems in allergy testing, where only small amounts of blood are available and many tests have to be carried out.

Bacteria-induced histamine release. Examination of the bacterial cell wall components peptidoglycan, teichoic acid and protein A

The histamine-releasing capability of whole bacteria was examined in leukocyte suspensions from normal individuals. Both gram-positive and gram-negative bacteria caused basophil histamine release. It is probably the bacterial cell wall which interacts with the basophil cell surface leading to release of histamine, since cell walls showed higher histamine releasing capability than the whole bacteria. The releasing effect of the bacterial cell wall components peptidoglycan, teichoic acid and protein A was examined. The peptidoglycan preparations were found to be more potent than the corresponding whole bacteria and cell walls. Since peptidoglycan is found in the cell wall of both gram-positive and gram-negative bacteria, it might be a common factor responsible for histamine release by different bacteria. No release was obtained by teichoic acid, whereas protein A caused histamine release in leukocytes from allergic patients, but only a poor release in normal individuals. The initial step in protein A-induced histamine release might be a binding of protein A to IgE on the cell surface, since removal of cell-bound IgE reduced the release and a high correlation was found between protein A- and anti-IgE-induced histamine release.

Functional compartmentation of glycolytic versus oxidative metabolism in isolated rabbit heart

To investigate whether energy derived from glycolytic and oxidative metabolism are preferentially used for different functions in heart, tension, intracellular potential, and extracellular [K+] and pH (using triple barrel K/pH electrodes, tip diameter 0.5 mm) were monitored in isolated arterially perfused rabbit interventricular septa during exposure to hypoxia and metabolic inhibitors. Myocardial content of high energy phosphates, lactate, and glycogen were determined under the same conditions. Inhibiting oxidative metabolism with hypoxia, dinitrophenol (10(-5)M), or Na-azide (10(-3)M) caused marked suppression of tension (by 73 +/- 5, 65 +/- 8, and 50 +/- 14%, respectively) and a small increase in [K+]0 (0.8 +/- 0.4, 0.5 +/- 0.25, and 0.4 +/- 0.2 mM, respectively) after 10 min. Inhibiting glycolysis with iodoacetate (IAA) (10(-3)M) had a much smaller suppressant effect on tension (28 +/- 24%) but markedly increased [K+]0 accumulation (by 1.8 +/- 1.1 mM) at 10 min. These differences, when IAA was compared individually to the other interventions, were highly significant. The shortening of action potential duration was not significantly different for the four interventions. pH0 increased slightly during IAA (+0.04-+0.06 U) and fell during the other interventions (-0.10--0.16 U), but this did not account for the differences in [K+]0 accumulation and tension between inhibition of glycolytic vs. oxidative metabolism. Except for hypoxia, total cellular content of high energy phosphates was not significantly depressed under the various conditions. This data suggests that energy from glycolysis is preferentially used to support sarcolemmal function (as manifested by K+ loss), whereas oxidatively derived energy preferentially supports contractile function. Indexing terms: cardiac metabolism, extracellular pH, metabolic inhibitors, hypoxia, extracellular K+ accumulation, and glycolysis.

Intracellular pH and contraction of isolated rabbit and cat papillary muscle: effect of superfusate buffering

The influence of external buffering on surface pH (pHs), intracellular pH (pHi) and developed twitch tension was investigated in rabbit and cat papillary muscle. pHs and pHi were measured using single and double-barreled microelectrodes respectively. In 20 mM HEPES buffered solution, steady state pHi is close to that in control CO2/HCO-3 (25 mM HCO-3, 5% CO2) solution. pHs and developed tension also do not differ greatly from their control values. Decreasing the HEPES concentration to 5 mM, at constant external pH, lowers pHs considerably. The surface acidosis is associated with a small intracellular acidification; steady state pHi in 5 mM HEPES is always more acid than that in control CO2/HCO-3. A significant decrease in developed tension is also seen in 5 mM HEPES. Alteration of the superfusion velocity influences pHs only slightly. Stimulation of the muscle at high frequency is shown to increase surface acidification, the extent of which is dependent on the buffer concentration. The conclusion from the present experiments is that in papillary muscle external buffering influences intracellular pH and contraction via its effect on pHs.

Staphylococcus aureus peptidoglycan induces histamine release from basophil human leukocytes in vitro

Whole killed cells, cell walls, and peptidoglycans of Staphylococcus aureus were found to release histamine from human leukocytes and isolated rat mast cells in vitro. The histamine-releasing capability increased in the order of whole bacteria, cell walls, and peptidoglycans. Peptidoglycan was found to release histamine by a nonimmunological mechanism, as demonstrated by release in cells deprived of surface immunoglobulins, whereas whole bacteria and cell walls seemed to operate both by immunological and nonimmunological mechanisms. Histamine release was not a specific property of S. aureus; a wide range of whole bacterial species had this activity. We suggest that peptidoglycan may be a common factor responsible for histamine release by different bacteria.

Some hormonal effects on myocardial phosphate efflux

The effects of 23 agonists on the rates of cellular 32P efflux and lactate dehydrogenase (LDH) release were tested in a perfused rat heart preparation which had been prelabelled in vitro with [32P]Pi. Some 13 compounds produced detectable changes at high doses within 10 min, and in most cases a polyphasic response was observed. Six classes of compound gave rise to substantial effects, as follows. Catecholamines and glucagon produced a transient initial stimulation of Pi efflux, followed by a long-term inhibition of Pi transport and an increased rate of LDH release. These effects were clearly different from the response seen after treatment with dibutyryl cyclic AMP, which had a slower, stimulatory, effect on Pi output in doses which gave rise to a pronounced inotropic effect, and produced a marked increase in both coronary flow and LDH release. Carbachol also gave rise to a large transient stimulation of Pi efflux, which was followed by smaller sustained increase in Pi output without any obvious effect on LDH release. Dibutyryl cyclic GMP had no effect on Pi efflux or LDH release. Insulin decreased the rate of Pi efflux, although the loss rate partially recovered towards the control value after prolonged exposure to the hormone. Insulin had no obvious inotropic effects and produced no change in the rate of LDH release. Corticosteroids increased the rate of Pi efflux, although the loss rate partially declined towards the control value with prolonged exposure to the hormones. Corticosteroids produced a very slight inotropic response, and large doses sometimes increased the rate of LDH release from the tissue. Aldosterone slightly stimulated Pi output. A small, transient and somewhat variable stimulation of Pi efflux was observed with vasopressin and angiotensin, whereas tri-iodothyronine was slightly inhibitory, but adenosine, histamine, spermidine, des-Asp1-angiotensin, prolactin, parathyroid substances, calcitonin and somatostatin had no significant effects under our experimental conditions. Ouabain stimulated Pi efflux in doses that had no detectable inotropic effect. It is suggested that Pi efflux involves the electroneutral transport of NaH2PO4 across the cardiac plasmalemma and that many of the hormonal effects might be explained by changes in the intracellular [Na+] and pH in addition to changes in the intracellular [Pi].

Allergic and pseudo-allergic reactions caused by penicillins, cocoa and peppermint additives in penicillin factory workers examined by basophil histamine release

Allergic and pseudo-allergic reactions were examined in penicillin factory workers exposed to the dust of preparations of pivampicillin and pivmecillinam. Among 14 workers basophils from five persons showed histamine release by challenge with penicillins, whereas no release was observed in controls of non-atopic individuals not working with the manufacturing of penicillin. Positive skin response was obtained in four workers by path testing and in three persons by scratch test revealing late but no immediate response. All the eight workers who were also exposed to flavour additives used in the penicillin preparations showed histamine release by cocoa and peppermint. The release was not changed by removal of immunoglobulins from the basophil cell surface and the additives caused a similar release in the controls. The histamine release caused by cocoa and peppermint therefore depend on non-immunological mechanisms, i.e. pseudo-allergic reactions which might contribute to the symptoms in penicillin factory workers.

Complexity of lectin-mediated reactions in bacteria-induced histamine release

We have earlier suggested that bacteria-induced histamine release is caused by different mechanisms, including allergic and non-immunological mechanisms, and that the latter probably depends on lectin-mediated reactions. Two possibilities of lectin-mediated reactions were examined in this study, bacterial surface lectins bind to sugars on the basophil cell membrane leading to histamine release, and the reverse reaction where bacterial aminosugars react with lectins on the basophil cell surface. In the bacterial histamine release caused by the Staph. aureus strain Wood 46 it was possible to demonstrate a reverse reaction, but not a bacterial lectin-mediated reaction. The reaction seems to be complex, as lower concentrations of sugars might potentiate the release of histamine by binding to the target cell or bacteria, while the release is inhibited by higher concentrations.

Bacterial histamine release by immunological and non-immunological lectin-mediated reactions

The mechanisms of bacteria-induced histamine release were examined in vitro in human leukocytes and rat mast cells. Three types of bacterial responders were found. In persons with IgE-bearing basophilocytes bacterial histamine release could be triggered by two different mechanisms, an IgE-dependent mechanism where removal of IgE abolished the release and a non-immunological mechanism where this was not the case. In responders with no IgE-bearing cells bacterial histamine release was caused by a non-immunological mechanism. The non-immunological mechanism was further substantiated by release in isolated mast cells from germ-free rats. These experiments suggest a direct interaction between bacteria and target cell, and experiments with multi-washed bacteria and bacteria cell wall preparations indicate the possibility of the bacteria wall interacting with the target cell. It is probable that the non-immunological mechanism depends on lectin-mediated reactions, since bacteria-induced histamine release was inhibited by lectin-binding sugars as is release caused by plant lectins.

Potassium and the heart

The electrical stability of the heart is more sensitive to the extracellular than to the intracellular potassium concentration. During exercise, extracellular potassium varies rapidly. Catecholamines also modulate the plasma potassium concentration. Hypokalaemia of any cause can precipitate arrhythmias. Ischaemic myocardium loses potassium into the extracellular space within seconds and the cell becomes depolarized. The rise of the extracellular potassium ion concentration accounts for many of the early electrophysiological changes. Abrupt changes of plasma potassium concentration in normal myocardium and a high potassium concentration in ischaemic myocardium can set up electrical forces which initiate arrhythmias. The same phenomenon can account for changes on the electrocardiogram early after the cessation of an exercise test in a patient with ischaemic heart disease. Accumulation of potassium between cells in response to an increase of heart rate is a possible mechanism for false positive exercise tests and Syndrome X.

Increased leucocyte histamine release by Entamoeba histolytica antigen in patients with amoebic abscess of the liver

Leucocytes (basophils) from non-atopic adult subjects living in an area highly endemic with Entamoeba histolytica release histamine in a dose-dependent fashion upon in vitro exposure to an antigen of axenically grown E. histolytica (histolyticin). Leucocytes of patients with acute amoebic liver abscess were significantly more sensitive to this antigen than leucocytes of control subjects, including patients that had recovered from amoebic liver abscess. By comparison Concanavalin-A induced histamine release found in patients with amoebic liver abscess and healthy controls suggest an immunological mechanism for histolyticin induced in vitro histamine release. This is also suggested by the inability of histolyticin to release histamine from leucocytes of healthy newborn infants and the significant fall in sensitivity to histolyticin following incubation of leucocytes in acid pH. Histamine and other mediators may contribute locally to the early intense inflammatory reaction observed in tissue invasion by E. histolytica.

Lectin-mediated reactions in histamine release caused by bacteria

The bacteria-induced release of histamine was studied in human basophil leukocytes and in isolated rat mast cells. Whole bacteria of Staph. aureus caused release in a 98% pure population of peritoneal mast cells from germ-free rats, indicating a non-immunological mechanism and a direct interaction between the bacteria and the target cells. Probably the bacterial cell wall interacts with the cell membrane, since a preparation of the bacterial cell wall caused a dose-dependent release of histamine from basophil leukocytes similar to that induced by whole bacteria, and repeated washing of whole bacteria did not change the release. Inhibition studies by lectin-binding sugars indicate that aminosugars on the bacterial surface of Staph. aureus interact with lectins on the basophil cell membrane leading to histamine release.

A new method for detecting histamine release

Glass microfibres have been found to bind histamine with high affinity and selectivity. A new test for measuring basophil histamine release has been developed using the glass microfibres as a solid phase. Glass microfibres are crushed and fixed to the bottom of microtitre plates with a water-soluble glue. Histamine release is performed in the glass microfibre -prepared microtitre plates by challenging 100 microliter washed blood with 20 microliter antigen per well for 90 min at 37 degrees C. Released histamine is bound with high affinity to the glass microfibres , since 90% of histamine in the solution is adsorbed to the fibres. After incubation the microtitre plate is washed with H2O to remove cells and interfering substances. Fibre-bound histamine is detected by the fluorometric o-phthaldialdehyde method. The sensitivity of the assay is 0.63 ng histamine, 2 HCl and the histamine standard curve is linear up to at least 5 ng histamine, 2 HCl. Optimal conditions for the new assay are described. After challenge with anti-Ige a comparison with the conventional histamine release from Ficoll-Hypaque-isolated leukocytes showed almost identical results.

Type I allergy to normal cellular constituents in chronic inflammatory bowel disease? Results from basophil histamine release test compared with total IgE and antinuclear antibodies

The possibility of autoimmune type I reactions to cellular constituents was investigated in 22 patients with ulcerative colitis, 12 with Crohn's disease, and in 22 healthy volunteers. Nuclear components and colon mucosa fragments were tested as potential antigens by the basophil histamine release technique. One of 12 patients with ulcerative colitis responded to sonicated leukocyte nuclei and one of 12 patients with Crohn's disease responded to both nuclei and RNA. Increased serum levels of total IgE and antinuclear antibodies of IgE class were found in one and three of the 24 patients, respectively. Histamine release caused by colon mucosa fragments was not observed in a separate study consisting of 10 ulcerative colitis patients and 10 healthy volunteers. Autoimmune type I allergy to cellular constituents does not seem to be of significance for chronic inflammatory bowel disease and thus could not explain the involvement of tissue mast cells and eosinophils in this condition.

Basophil histamine release induced by leukocyte nuclei in patients with rheumatoid arthritis

Leukocyte suspensions containing basophils were obtained from 23 patients with rheumatoid arthritis (RA). When these cells were incubated with leukocyte nuclei from normal persons, histamine release was seen in 11 of the 15 patients with active disease, but not in the quiescent group or in normal individuals. The dose-response curve for histamine release was similar to that obtained by specific antigen in type I allergy. By removal from and refixation to the cells of surface Ig, the release of histamine was respectively, abolished and restored, just as in similar experiments in hay fever patients. The dependence of pH for removal was also identical with that found in type I allergy. Antinuclear antibodies of the IgE class (IgE ANA) mainly directed against the granulocyte nuclei were often found in serum and on the cell surface of the RA patients, but not in normal individuals. A correlation was found between these titres in serum and on the cell surface. No correlation was found between ANA in serum and on the cell surface, on the one hand and disease activity and histamine release on the other. In a group of 12 patients with another joint disease, osteoarthrosis, only two patients showed histamine release, and in contrast to the other patients they showed swelling of more than two joints. The present investigation supports our hypothesis of an involvement of an autoimmune type I reaction directed against nuclear components in the RA disease.

Inhibitory effect of calcium antagonists on histamine release from human leukocytes. In vivo and in vitro experiments

A study was made of the influence of calcium antagonists on human basophil histamine release induced in vitro by specific antigen, anti-IgE or the calcium ionophore A23187. Both verapamil, nifedipine, and nimodipine were found to inhibit the release, and a similar effect was also observed after peroral administration of verapamil and nifedipine. The inhibitory effect of the drugs on histamine release seems to depend on interaction with calcium at different sites. The anti-allergic effect might explain the improvement found with calcium antagonists in exercise-induced asthma.

Myocardial protection during surgical coronary reperfusion

Reperfusion injury in the surgical setting is defined as those metabolic, functional and structural consequences of restoring coronary flow (that is, aortic unclamping and revascularization) that can be avoided or reversed by modification of the conditions of reperfusion by the operating surgeon. The potential for reperfusion damage exists during cardiac surgery because temporary myocardial ischemia (that is, aortic clamping) is needed to produce a quiet, bloodless surgical field. Cold cardioplegic techniques have decreased the risks of ischemic myocardial damage during aortic clamping, but reperfusion damage can still occur when there is poor cardioplegic distribution (that is, coronary artery disease) or in hearts that have suffered ischemic damage before extracorporeal circulation is started (such as extending myocardial infarction, cardiogenic shock and the like). The surgical setting affords the ideal opportunity for reperfusate modification because the components and conditions of the reperfusate are in the surgeon's control. This study reviews present understanding of the nature of reperfusion damage in the surgical setting and summarizes studies over the past 6 years which suggest that much of reperfusion damage can be avoided or reversed by adjusting the temperature, pressure and composition of reperfusate blood.

Mechanism of action of Bacillus thuringiensis var israelensis insecticidal delta-endotoxin

Bacillus thuringiensis var israelensis delta-endotoxin protein active against mosquitoes was inactivated by prior incubation with lipids extracted from Aedes albopictus cells. Experiments with lipid dispersions and multilamellar liposomes showed that the toxin binds to phosphatidyl choline, sphingomyelin and phosphatidyl ethanolamine provided these lipids contain unsaturated fatty acids. Phosphatidyl serine binds toxin less efficiently and phosphatidyl inositol, cardiolipin, cerebroside and cholesterol show no affinity for the toxin. The results suggest an insecticidal mechanism in which interaction of toxin with affinity for the toxin. The results suggest an insecticidal mechanism in which interaction of toxin with specific plasma membrane lipids causes a detergent-like rearrangement of the lipids, leading to disruption of membrane integrity and eventual cytolysis.

Intrinsic asthma and bacterial histamine release via lectin effect

Bacteria-induced histamine release from basophil leukocytes was observed in vitro in both children with intrinsic asthma (IA) as well as in normal individuals. In vivo the release is suggested to take place only in the lung of IA patients, where a defective pulmonary barrier would permit the bacteria to enter, but not in healthy individuals. The study indicates that two different mechanisms of bacterial histamine release might exist, an IgE-mediated reaction and a non-immunological mechanism consisting of a direct interaction with the basophil cell surface. The non-allergic mechanism might depend on a lectin effect where bacterial surface lectins interact with the basophil cell surface leading to release of histamine. Inhibition studies with carbohydrates suggest a multi-lectin reaction in the bacterial histamine release involving several types of lectins on the bacterial membrane reacting with different carbohydrate moieties on the cell surface of basophil leukocytes.

Immunotherapy with grass pollen major allergens. Immunological results from a prospective 3-year double blind study

Preseasonal hyposensitization stimulated an intercorrelated increase in both serum-specific IgE and allergen-specific IgG. Subsequent perennial treatment depressed the stimulated IgE response and the basophil cell sensitivity, whereas the allergen-specific IgG response showed further increase and persisted at a high level. Nasal IgE response was stimulated from the second pollen season and subsequently became depressed. One year after the end of hyposensitization the allergen-specific IgG response had fallen by 25-50%.

The effects of verapamil, quiescence, and cardioplegia on calcium exchange and mechanical function in ischemic rabbit myocardium

The effects of verapamil (1 mg/liter, 2 x 10(-6) mol/liter), quiescence, and cardioplegia (K+ 16 mmol/liter, Mg2+ 16 mmol/liter) on calcium exchange and mechanical function during ischemia and reperfusion have been investigated in the rabbit interventricular septum at 32 degrees C. Calcium influx and efflux were recorded continuously with 47Ca2+ and 45Ca2+. After 60 minutes of total ischemia and reperfusion for 30 minutes, there was a net calcium gain of 4.9 mmol/kg dry tissue. Verapamil given before total ischemia reduced net calcium gain to 1.5 mmol/kg dry tissue (n = 5, P less than 0.03). When given only on reperfusion after total ischemia, or 10 minutes before reperfusion during low flow ischemia, verapamil did not affect calcium exchange. Cardioplegia begun 10 minutes before total ischemia reduced net calcium gain to 1.0 +/- 0.26 mmol/kg dry tissue (n = 6, P less than 0.001). Cardioplegia during the first 10 minutes of reperfusion, or lack of electrical stimulation during reperfusion, did not reduce calcium gain. Net calcium gain correlated with the maximum rise in resting tension and with the recovery of developed tension. In control experiments neither verapamil nor cardioplegia altered influx or efflux of slowly exchanging calcium. The cardioprotective effects of cardioplegia and the calcium channel blocker verapamil appear to be due to a reduction of myocardial work rather than to any specific direct action on calcium fluxes across the myocardial cell membrane.

The effect of pH on the transient-state kinetics of Ca2+-Mg2+-ATPase of cardiac sarcoplasmic reticulum. A comparison with skeletal sarcoplasmic reticulum

The effect of pH on the Ca2+-Mg2+-dependent ATPase of sarcoplasmic reticulum (SR) was investigated with a rapid mixing quench-flow apparatus capable of measuring phosphorylation and dephosphorylation at times as rapid as 4 msec. The rates of formation and decomposition of the phosphorylated intermediate (E approximately P) of the Ca2+-Mg2+-ATPase were studied in the pH range between 7.6 and 6.0. At pH 6.8, the rates of formation of the phosphorylated intermediate of the Ca2+-Mg2+-ATPase of sarcoplasmic reticulum are the same (t1/2 = 10 msec) for cardiac and skeletal sarcoplasmic reticulum preloaded with calcium, but decrease as the pH is lowered. The effect of acid pH (6.0) is more pronounced for cardiac sarcoplasmic reticulum (t 1/2 = 47 msec) than for skeletal sarcoplasmic reticulum (t 1/2 = 17 msec), in agreement with studies showing that acidosis has a more pronounced effect on cardiac muscle than on skeletal muscle. In addition, a decrease in pH results in a decrease in the rate of the E approximately P decomposition step (the slowest step in the SR reaction sequence). The E approximately P decomposition half-lives were observed to be 97 and 77 msec, respectively for cardiac and skeletal SR at pH 6.8. At pH 6.0, the half-lives were increased to 136 and 178 msec for cardiac and skeletal SR, respectively.