Mechanism of inhibition of IgE-dependent histamine release from rat mast cells by xestobergsterol A from the Okinawan marine spongeXestospongia bergquistia

Histamine release from rat peritoneal mast cells induced by anti-IgE was essentially complete within 4–5 min. Xestobergsterol A and B, which are constituents of the Okinawan marine spongeXestospongia bergquistia Fromont, dose-dependently inhibited anti-IgE-induced histamine release from rat mast cells. The IC₅₀ values of xestobergsterol A and B for histamine release in mast cells activated by anti-IgE were 0.07 and 0.11 M, respectively. Anti-IgE stimulated PI-PLC activity in a mast cell membrane preparation. Xestobergsterol A dose-dependently inhibited the generation of IP3 and membrane-bound PI-PLC activity. Moreover, xestobergsterol A inhibited Ca²⁺-mobilization from intracellular Ca²⁺-stores as well as histamine release in mast cells activated by anti-IgE. On the other hand, xestobergsterol B did not inhibit the membrane-bound and cytosolic PI-PLC activity, IP3 generation or the initial rise in [Ca²⁺]_i in mast cells activated by anti-IgE. These results suggest that the mechanism of inhibition by xestobergsterol A of the initial rise in [Ca²⁺]_i, of the generation of IP3, and of histamine release induced by anti-IgE, was through the inhibition of PI-PLC activity.     

Complex formation betweenγ-immunoglobulin and calmodulin in calcium-free conditions

We show that -immunoglobulin (IgG) binds calmodulin (CaM) in a Ca²⁺-independent manner, with Kd value of (1.7±0.5)×10^–7M. A single IgG molecule maximally bound 10 CaM molecules. The binding is to the heavy chain or Fab portion, but not the Fc portion, of the IgG molecules. Ca²⁺ greatly diminished the interaction between IgG and CaM, with IC₅₀=8–9M. These data give a novel insight into protein-protein interactions.     

An analysis of the effects of urethane on cardiovascular responsiveness to catecholamines in terms of its interference with Ca++ mobilization from both intra and extracellular pools

Summary Urethane (1×10^–2–1×10^–1 M) reduced, in a concentration-dependent manner, both intra and extracellular Ca⁺⁺ dependent noradrenaline-induced contractions of perfused rabbit ear artery as well as the tonic contractions produced by perfusion with high K⁺ solution. However, a quantitative analysis of the data indicated that for urethane concentrations similar to those found in plasma during anesthesia urethane antagonism is confined to noradrenaline-induced contractions which depend upon the mobilization of Ca⁺⁺ from intracellular storage sites. In KCl-contracted arteries, urethane enhanced the relaxant effects of isoprenaline.—Urethane reduced the amplitude of contractions of spontaneously beating guinea-pig right atrium at concentrations which have only a limited effect on frequency. In addition, it decreased in a concentration-dependent manner the amplitude of isoprenaline-activated electrically driven, and K⁺ depolarized guinea-pig right ventricular strips. Urethane had no effect on the chrono and inotropic actions of isoprenaline on cardiac preparations. In in vivo experiments the chronotropic response to low doses of isoprenaline was significantly higher in urethane-treated as compared to unanesthetized rats. The higher dose of isoprenaline tested produced a significant fall in systolic blood pressure in urethane-anesthetized rats. A significant correlation exists between the chronotropic response to isoprenaline and resting heart rate values in urethane-anesthetized rats. These results indicate that urethane, at concentrations similar to those found in plasma during anesthesia selectively interferes with mobilization of Ca⁺⁺ from intracellular storage sites. In addition, the interference of urethane anesthesia with the isoprenaline chronotropic effect in vivo cannot be explained by a direct interference of urethane with -adrenoceptors at cardiac level.     

Zinc ions block the second but not the first phasic response to repetitive application of carbachol and histamine in guinea-pig taenia caeci

In the presence of Zn²⁺ (0.3 mM), carbachol (10^–6 M) or histamine (10^–5 M) induced the phasic response in guinea-pig taenia caeci while the tonic response was markedly inhibited. However, when the muscles were kept in Zn²⁺-containing medium following the first stimulation with either carbachol or histamine, neither application of carbachol nor of histamine elicited another phasic contraction. Caffeine (25 mM) did not induce contraction in the presence of Zn²⁺. After the washing out of caffeine in the presence of Zn²⁺, however, the muscle did then develop the phasic response on the application of carbachol or histamine. In conclusion, Zn²⁺ did not affect the carbachol or histamine-induced Ca²⁺ release from the storage sites. However, when Zn²⁺ was continuously present, Ca²⁺ was not supplied to the storage sites. Furthermore, carbachol and histamine mobilized a common cellular Ca²⁺ store, but they activated Ca²⁺ release channels different from the ones activated by caffeine in the Ca²⁺ storage sites.     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10(6) cells/ml in a buffered salt solution and incubated for 1 h at 37 degrees C in 300 microliter volumes in the absence or presence (9 X 10(-4) M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8 X 10(-4)M) caused (in addition to basal release) a mean +/- SEM percent histamine release of 15.7 +/- 5.2 in the presence of Ca++ and 19 +/- 4.9 in the absence of Ca++ (p greater than 0.05). It is suggested that D-galactosamine does not require extracellular Ca++ for the release of histamine from the rat mast cell.     

Equilibrium constant for calcium ion and ascorbate ion

Summary The combination of calcium and ascorbic acid in water at 25°C has been examined by measuring the change of free calcium ion concentration as ascorbate was added in small increment to a solution of calcium. The data show clearly that complex formation between calcium ion and ascorbate ion occurred. At ionic strength =0.1–0.2, the equilibrium constant of Ca⁺⁺ and the singly-charged ascorbate ion has been measured to be 2.1 M^–1. The precision of the result is better than 5% and the accuracy is estimated to be better than 20%. The application of the equilibrium constants is discussed.     

Magnesium enhances human pancreatic elastase digestion of125I-labeled elastin

Summary The effect of some divalent cations, especially Mg⁺⁺, on elastinolysis by porcine or human pancreatic elastase has been determined using¹²⁵Iodine-labeled elastin as substrate. Elastin degradation was significantly increased in the presence of 10^–3 M Mg⁺⁺. If elastin was pre-incubated with 0.5 (w/v) Triton, there was a further increase in elastinolysis to 2.6 times the original rate.     

Der Einfluss von Acetylcholin auf den Calciumumsatz ruhender und kontrahierender Vorhofmuskulaturin vitro

Summary Acetylcholine 5 × 10^–8 g/ml reduces the Ca⁴⁵ uptake of the beating left atria of guinea-pig; the tissue calcium is not altered. In resting atria, acetylcholine 5 × 10^–7 g/ml has no influence upon the calcium content and Ca⁴⁵ uptake. It is concluded that acetylcholine acts by shortening the action potential duration and thereby reduces the release of cellular calcium per excitation.

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Mit grosszügiger Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Die Abhängigkeit der Ca++-Aufnahme isolierter Mitochondrien des Herzmuskels von der Na+-und K+-Konzentration als mögliche Ursache der inotropen Digitaliswirkung

Summary In isolated mitochondria of heart muscle from rabbits and oxen there is, under suitable conditions, an accumulation of Ca⁺⁺, which is significantly enhanced by elevating the K⁺/Na⁺ quotient of the incubation medium. K-strophanthine (10^–5–10^–7) does not influence the accumulation of Ca⁺⁺ by the mitochondria of heart muscle. Therefore the intracellular increase in exchangeable Ca⁺⁺ observed after digitalis-glycosides could be explained by a decrease of the intracellular K⁺/Na⁺ quotient, which is caused by inhibition of the membrane ATPase and diminishes the capacity for Ca⁺⁺ accumulation in mitochondria.     

Cartsian diver studies on respiration of rat bone marrow cells in the presence of erythropoietin and anti-erythropoientin

Résumé L'étude de la respiration des cellules de la moelle des os du rat fut faite avec un plongeur Cartésien. Ces cellules, avec ou sans glucose, repirent à raison de 0,73±0,15 et 0,97±0,17×10^–6 l O₂/cellule/h. Comparée aux mesures de contrôle, la respiration des cellules médullaires de rats pléthoriques est plus fabile en présence de ESF (0,45 contre 0,99×10^–6 l, O₂/cellule/h). Cette inhibition fut supprimée par la présence d'anti-ESF (0,98 contre 0,99×10^–6 l O₂/cellule/h).

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This research was supported by funds from a Damon Runyon Cancer Research Training Grant and the US Public Helath Seervice. The senior author was a Damon Runyon Post-Doctoral Traince.     

The effect of hydrocortisone and thyroxine on development of calcium homeostasis in embryonic intestinal epithelium

Cytoplasmic Ca²⁺ concentration of epithelial cells from 14-day embryonic chick duodena decreased during 72 h of organ culture to a value 54% of that found at 17 days in vivo. The ability of cells to maintain a constant Ca²⁺ concentration when challenged with high extracellular calcium was also significantly reduced. Addition of 1 M hydrocortisone during culture restored both parameters of Ca²⁺ homeostasis to that of 16-day uncultured duodena, and rise in cytoplasmic Ca²⁺ was significant within 4 h of hormone treatment. Thyroxine influenced epithelial Ca²⁺ similarly, but to a lesser degree and only after 48–72 h of culture. These data indicate that glucocorticoids, and possibly thyroid hormones, influence the development of calcium homeostasis in intestinal epithelium.     

Influence of ethanol on calcium,inositol phospholipids and intracellular signalling mechanisms

Summary Studies have implicated Ca⁺⁺ in the actions of ethanol at many biochemical levels. Calcium as a major intracellular messenger in the central nervous system is involved in many processes, including protein phosphorylation enzyme activation and secretion of hormones and neurotransmitters. The control of intracellular calcium, therefore, represents a major step by which neuronal cells regulate their activities. The present review focuses on three primary areas which influence intracellular calcium levels; voltage-dependent Ca⁺⁺ channels, receptor-mediated inositol phospholipid hydrolysis, and Ca⁺⁺/Mg⁺⁺-ATPase, the high affinity membrane Ca⁺⁺ pump.Current research suggests that a subtype of the voltage-dependent Ca⁺⁺ channel, the dihydropyridine-sensitive Ca⁺⁺ channel, is uniquely sensitive to acute and chronic ethanol treatment. Acute exposure inhibits, while chronic ethanol exposure increases⁴⁵Ca⁺⁺-influx and [³H]dihydropyridine receptor binding sites. In addition, acute and chronic exposure to ethanol inhibits, then increases Ca⁺⁺/Mg⁺⁺-ATPase activity in neuronal membranes. Changes in Ca⁺⁺ channel and Ca⁺⁺/Mg⁺⁺-ATPase activity following chronic ethanol may occur as an adaptation process to increase Ca⁺⁺ availability for intracellular processes. Since receptor-dependent inositol phospholipid hydrolysis is enhanced after chronic ethanol treatment, subsequent activation of protein kinase-C may also be involved in the adaptation process and may indicate increased coupling for receptor-dependent changes in Ca⁺⁺/Mg⁺⁺-ATPase activity.The increased sensitivity of three Ca⁺⁺-dependent processes suggest that adaptation to chronic ethanol exposure may involve coupling of one or more of these processes to receptor-mediated events.     

Hyposmotic shock-induced discharge in acontia ofCalliactis parasitica is blocked by gadolinium

On acontia ofCalliactis parasitica it was observed that mechanical stimuli applied by a gelatin probe, a method effective in tentacles of Anthozoa, do not induce the discharge of nematocytes. Hyposmotic shock, performed by treatment with NaCl solution 35% hyposmotic with respect to sea water, induces, in the presence of Ca²⁺, the discharge that spreads along the acontial filament, as previously observed following treatment with SCN^–. The hyposmotic shock-induced discharge is blocked by Gd³⁺ at a concentration of 1 M. 10 M Gd³⁺ prevents also the SCN^–-induced discharge. These results suggest the presence of stretch activated cation channels either in nematocytes and/or in supporting cells as well as a possible effect of SCN^– on this class of ion channels.     

Skinned smooth muscle: Time course of force and ATPase activity during contraction cycle

Summary The time course of ATPase activity and force has been determined during contraction and relaxation in skinned (hyperpermeable) anterior byssus retractor muscle, ABRM, ofMytilus edulis and compared with corresponding measurements on skinned taenia coli of guinea-pigs. Following a calcium-induced contraction, lowering the [Ca⁺⁺] to 10^–8 M rapidly reduces ATPase activity within 2 min to resting levels while force declines only to about 30–50% of maximal tension within the same time. Thus slow relaxation is due to a catch-like-state which is common to different kinds of smooth muscles and can be reduced with cAMP in ABRM and by P_i in taenia coli.The support by the Deutsche Forschungsgemeinschaft and the excellent technical assistance of Mrs K. Winnikes are gratefully acknowledged.     

Effects of cerebral lateral,ventricular infusions of phloridzin on feeding and body weight in Gallus domesticus (L.)

Summary Contrary to earlier findings in rats, cerebral lateral ventricular infusions of 1×10^–3 M or 2×10^–3 M solutions of phloridzin at a rate of 2.5 l/min for 90 min had no significant stimulating effects on food intake and weight gain in hens and cocks. These different responses to intraventricular phloridzin might reflect a difference of sensitivity to the inhibitory action of phloridzin on glucose transport in cerebral cells or certain peculiarities of mechanisms controlling food intake in chickens.     

Denaturation map of the ribosomal DNA ofLytechinus variegatus sperm

Summary Electron microscopy of the partially heat denatured ribosomal DNA (rDNA) from sea urchin (Lytechinus variegatus) sperm has demonstrated that it consists of repeating units of 3.6±0.2 m, corresponding to a mol.wt of 7.2±0.4×10⁶. Based on differential denaturability, each repeat unit is divided into 2 regions. The larger region of 2.47±0.11 m (mol.wt 4.9±0.22×10⁶) corresponds in length to the ribosomal precursor RNA of sea urchins and the smaller, GC-rich, subunit of 1.16±0.09 m (mol.wt 2.3±0.18×10⁶) is presumed to contain non-transcribed spacer sequences.Acknowledgments. This paper is dedicated to the memory of Dr D. P. Costello whose insprration made this work possible. I gratefully acknowledge the valuable advice of Drs D.W. Stafford and M.A. Bleyman.     

Potentiating action of hexoprenaline on14C-aminopyrine uptake by isolated rat parietal cells

Summary Hexoprenaline potentiated the¹⁴C-aminopyrine uptake (a reliable index of H⁺ generation) of isolated rat gastric cells stimulated by 10^–6–10^–4 mol/l carbachol, and inhibited that in response to 10^–4 mol/l histamine without and in the presence of propranolol. It is concluded that hexoprenaline acts as a partial agonist on parietal cell H₂-receptors and that -adrenoceptor activation may functionally modualte gastric acid secretion.Acknowledgments. S. Maliski, Institute of Rheumatology, Warszawa, held a fellowship of the Alexander v. Humboldt-Foundation. The study was supported by the Deutsche Forschungsgemeinschaft. The skilful technical assistance of Mrs R. Maier and Mr R. Beer is gratefully acknowledged.     

Calcification in implants of tendon

Zusammenfassung Behandlung von Hasenmuskeln vor der Implantation mit Kalzium- und Phosphatlösungen bei 2C ergibt Mineralisierung der Sehnen bis zu 60–80%, mit 15 molaren Kalziumlösungen bis zu 8–23%. Zur Kalzifikation sind grössere Ca⁺⁺-Mengen nötig: werden gleichzeitig Kalzium- und Phosphationen verwendet, so sind kleinere Mengen zur vermehrten Apatitablagerung notwendig.     

Ba++ induced square-shaped potential waves in molluscan neurones

Summary Rhythmic slow square-shaped potential waves lasting 20–50 sec are induced in Aplysia neurones when Ca⁺⁺ is replaced by Ba⁺⁺. During the plateau, the membrane is highly permeable to Ba⁺⁺ ions, whereas in the inter-wave period the membrane resistance increases by 60 times. Analysis with slow current ramps suggests that the membrane properties of Ba-treated neurones and normally burst-generating neurones are similar.     

Methyllycaconitine,a naturally occurring insecticide with a high affinity for the insect cholinergic receptor

Summary Studies of extracts ofDelphinium seeds, long known to be insecticidal, revealed that a principal insecticidal toxin was methyllycaconitine, which is shown to be a potent inhibitor of -bungarotoxin binding to housefly heads (K_inh=2.5×10^–10±0.5×10^–10M).Calgary for gifts of MLA, citrate and lycoctonine, and Dr W. Bowers of the University of Arizona for the original extract ofDelphinium seeds. We would also like to acknowledge the able technical support of Ms C. Dushin, Mr E.L. Bowman, Dr C. C. Gagne, Mr R. F. Borysewicz and Dr P. Mowery for his assistance in obtaining and interpreting the carbon-13 NMR spectra.