Hydrocortisone inhibits antigen-induced rise in intracellular free calcium concentration and abolishes leukotriene C4 production in leukemic basophils

Antigenic stimulation of rat basophilic leukemia cells (RBL-3H3) elevates intracellular free Ca²⁺ concentration ([Ca²⁺]_i) and induces production of leukotriene C₄ (LTC₄). This model was used to examine the role of Ca²⁺ in LTC₄ formation, and inhibition by hydrocortisone (HC). HC, at a physiological concentration (2×10⁻⁷M), selectively prevented the stimulatory effect of the antigen on LTC₄ production whereas the response to calcium inophore (A23187) remained unimpaired. The inhibition by HC was time-dependent: half maximal response was reached at 2 hour and maximal response at 3 hours. Addition of arachidonic acid (3 μg/ml) did not overcome the inhibitory action of HC. An elevated [Ca²⁺]_i is known to be essential for the activation ob both 5-lipoxygenase and phospholipase A₂. The stimulatory effect of the antigen on LTC₄ production was abolished when the cells were incubated in Ca²⁺-deficient medium. Likewise, calcium ionophore stimulation shows dependence on extracellular Ca²⁺. Half maximal stimulation by the antigen and calcium ionophore was observed at external Ca²⁺ concentration of 150 μM and 40 μM respectively. Treatment with HC largely prevented the antigen-induced rise in [Ca²⁺]_i, measured by Quin 2. In addition, HC reduced by 70% the accumulation of ⁴⁵Ca²⁺ induced by the antigen. Collectively, these results demonstrate for the first time that HC reduces antigen-induced elevation of [Ca²⁺]_i, and this may be associated with the inhibitory action of HC on LTC₄ formation. This property could be partly responsible for the antiallergic and antiinflammatory activities of HC.     

Islet-cell Carcinoma (Zollinger—Ellison Syndrome) with Fulminating Adrenocortical Hyperfunction and Hypokalemia

The production of ACTH-like material by tumours arising in non-endocrine tissue may initiate severe adrenocortical hyperfunction. The pathogenesis and clinical and laboratory features of Cushing''s syndrome associated with such tumours are characteristic. The autonomous production by the tumour of ACTH-like material cannot be suppressed by exogenous corticoids. The onset of clinical symptoms is rapid; muscle wasting, general weakness, thirst and peripheral edema predominate, and the classical signs of Cushing''s syndrome may be absent. High levels of plasma 17-hydroxycorticosteroids and urinary 17-hydroxycorticosteroids and 17-ketosteroids, usually with normal levels of urinary aldosterone, commonly occur. Hypokalemic alkalosis unresponsive to replacement therapy may cause death. In the case reported herein, the intriguing possibility exists that two hormone-like substances were produced by the primary growth and its metastases: one, ACTH-like, to account for the adrenal hyperplasia and Cushing''s syndrome; and another, gastrin-like, giving rise to the ulcerogenic diathesis.     

Monoclonal antibody AA4, which inhibits binding of IgE to high affinity receptors on rat basophilic leukemia cells, binds to novel alpha-galactosyl derivatives of ganglioside GD1b

Mouse monoclonal antibody AA4 inhibits the binding of IgE to high affinity IgE receptors on the rat basophilic leukemia cell line RBL-2H3. As shown by immunostaining of thin layer chromatograms, antibody AA4 binds avidly to two disialogangliosides (antigen I and antigen II) that occur in this cell line. The two antigens were purified by anion exchange chromatography followed by short-bed continuous thin-layer chromatography. About 230 micrograms of antigen I and 60 micrograms of antigen II were obtained from 20 g (wet weight) of leukemia cells. The structures of both purified antigens were determined to be alpha-galactosyl derivatives of the ganglioside GD1b by fast atom bombardment-mass spectrometry, by chemical ionization-mass spectrometry of permethylated samples, by gas chromatography-mass spectrometry of partially methylated alditol acetates, and by treatment with exoglycosidases and mild acid hydrolysis. The structure of antigen I is: (formula; see text) Antigen II has an additional alpha-galactosyl residue as follows: (formula; see text) The ceramide of antigen I contains approximately equal amounts of C24:0, C22:0, C20:0, C18:0, and C16:0 N-acyl fatty acids. The ceramide base is predominantly sphingosine along with a small amount of dihydrosphingosine. In contrast, the ceramide of antigen II contains mainly C24:0 N-acyl fatty acid with much lower amounts of C22:0, C20:0, and C18:0 fatty acids. Moreover, the ceramide base is approximately 55% sphingosine and 45% dihydrosphingosine. No unsaturated N-acyl fatty acids were detected in either antigen.     

Effect of small doses of X-rays on formation of colour variants bySerratia marcescens

1. (1)
   Клетки Serratia marcescens, которые выжили после повторных облучений лучами Х, при новй однокртном облучении процент цветных мутантов. Процент мутаций возрастает в зависимости от дозы облучения ночти линейно.     

Endotoxic lipid A interaction with human platelets. Structure-function analysis of lipid A homologs obtained from Salmonella minnesota Re595 lipopolysaccharide

We previously reported that human blood platelets are directly stimulated by endotoxic Lipid A via the protein kinase C pathway (Grabarek, J., Timmons, S., and Hawiger, J. (1988) J. Clin. Invest. 82, 964-971). To study the relationship between the molecular structure of Lipid A and its ability to activate human platelets, we used Lipid A homologs derived from Salmonella minnesota Re595 lipopolysaccharide. Preparations of Lipid A are heterogeneous in regard to the degree of substitution of fatty acids which result in multiple homologs. These were separated by thin-layer chromatography and characterized by fast atom bombardment spectroscopy and related techniques (Johnson R. S., Her, G.-R., Grabarek, J., Hawiger, J., and Reinhold, V. N. (1990) J. Biol. Chem. 265, 8108-8116). The homologs of monophosphoryl Lipid A (MLA) present in fractions TLC-8 (heptaacyl MLA ion, m/z 1953), TLC-7 (three hexaacyl species with predominant MLA ion m/z 1715), and TLC-6 (four pentaacyl homologs with predominant MLA ion, m/z 1505) induced secretion of [14C]serotonin and aggregation of platelets. Lipid A homologs in fractions TLC-5 (three tetraacyl MLA ions, m/z 1323, 1307, and 1279), TLC-4 (one major triacyl MLA ion, m/z 1097), TLC-3 (tetraacyl MLA ion, m/z 1278), TLC-2 (a diphosphoryl hexaacyl Lipid A ion, m/z 1795, and several ions of low abundance), and TLC-1 (two ions, m/z 1097 and 666) were not active in regard to human platelet aggregation and [14C]serotonin secretion. The most active homolog was heptaacyl MLA ion, m/z 1953, present in TLC-8, while homologs present in TLC-7 and TLC-6 were 5 and 10 times less active, respectively. Rapid phosphorylation of a human platelet protein of Mr 40,000-47,000 (P47), a substrate for protein kinase C activation, preceded secretion of serotonin when platelets were triggered by the most active heptaacyl MLA ion, m/z 1953. These events were time-dependent, with half-maximal response of phosphorylation of P47 at 30 s and [14C]serotonin secretion at 45 s. A marked difference in the degree of phosphorylation of P47 was observed with heptaacyl MLA homolog present in TLC-8 inducing complete phosphorylation (97%), whereas less acylated Lipid A homologs present in TLC-1 caused marginal phosphorylation (20%). These results indicate that the degree of acylation of monophosphoryl Lipid A determines its functional properties toward human platelets in regard to secretion of [14C]serotonin, aggregation, and activation of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)     

A novel action of glucocorticosteroid in inhibition of leukotriene C4 production by rat basophilic leukemia cells: suppression of the elevation of cytosolic free Ca2+ induced by antigen

Rat basophilic leukemia (RBL-2H3) cells serve as a model to examine the role of elevated internal Ca2+ concentration ([Ca2+]i), following antigen (DNP10BSA)-induced stimulation of leukotriene C4 (LTC4) formation. A novel action of hydrocortisone (HC), to reduce increased [Ca2+]i and consequently inhibit LTC4 formation is assessed. Half-maximal time for elevation of [Ca2+]i induced by antigen was less than 1 min, and maximal elevation of [Ca2+]i (3-fold increase) was reached within 2-3 min. This high [Ca2+]i level waned gradually by 27% during 20 min of incubation. For induction of LTC4 formation, however, there was a refractory period of about 2 min, and half-maximal elevation was at 11 min. Following pretreatment with HC, the antigen-stimulated increase in [Ca2+]i was stunted by 41% at 2-3 min and by 73% at 20 min. LTC4 formation was almost abolished. There was a lag period of at least 2 h to observe any inhibition in both parameters, and the maximal inhibition was about 4 h. Cycloheximide, and receptor antagonist to glucocorticosteroid (RU486) completely prevented the inhibitory effects of HC on elevated [Ca2+]i and LTC4 formation. Estradiol and aldosterone (each at 2.10(-6) M) were virtually inactive, while another glucocorticosteroid, dexamethasone (2.10(-7) M) markedly suppressed antigen induction in both parameters. It is proposed that the inhibitory effect of HC on the formation of LTC4 could be attributed mainly to its ability to reduce elevated [Ca2+]i.     

Adsorption and narcosis

Summary The adsorption of homologic alcohols by the sap ofCaulerpa prolifera was studied.It was found that the alcohols are adsorbed in an indirect relation to their respective capillary activities against air.Traube's rule is therefore not valid for this adsorption.It is supposed that the unadsorbed remainder is the cause of the narcotic effect and that the adsorption is a regulating device to remove the narcotizing substance from the more liquid phase of the cell interior.The validity ofTraube's rule for narcosis as a biological phenomenon can be understood on the basis of the fact, that the strongly capillary active substances are adsorbed at least and the little capillary active substances at most. Thus their narcotizing effect is indirectly proportional to their respective adsorbility.