Intravenous methylprednisolone efficacy in status asthmaticus of childhood.

Forty-nine nonsteroid-dependent children hospitalized with status asthmaticus were randomized to receive IV placebo or methylprednisolone treatment (1 mg/kg every six hours). All patients received nebulized isoetharine inhalations and continuous IV aminophylline infusion. Twenty-four hours after admission, the methylprednisolone-treated patients demonstrated a greater rate of improvement in their clinical scoring index than did placebo-treated children. However, the duration of hospital stay was not significantly shortened. Twenty-eight of the patients performed serial bedside spirometry at 0, 12, 24, and 36 hours after admission. The methyl-prednisolone-treated patients experienced a more rapid recovery from peripheral airway obstruction as measured by forced expiratory flow rate during 25% to 75% of forced vital capacity (FEF25-75). The magnitude and rate of improvement in FEF25-75 was significantly greater at 36 hours (P less than .05) and independent of changes in peak expiratory flow rate, forced vital capacity, or forced expiratory volume in the first second of forced vital capacity. Placebo-treated patients had a higher incidence of asthma relapse within 4 weeks of discharge (eight v two relapses, P less than .05). Findings of this study indicate that IV corticosteroid therapy is beneficial in treating pediatric status asthmaticus.

Characteristics of diatrizoate-induced basophil histamine release.

Factors influencing the release of histamine by basophils exposed to the radiocontrast agent diatrizoate were investigated in vitro by use of cells from healthy adult subjects with no history of radiocontrast reactions. Diatrizoate-induced release shared similarities with calcium ionophore-induced release. The response to both agents is dose dependent, enhanced by deuterium oxide, optimal at 37 degrees C, calcium dependent, and enhanced with longer reaction times. Unlike calcium ionophore, however, pretreatment of basophils with diatrizoate may also induce dose-dependent inhibition of reactivity during subsequent challenges with anti-IgE, N-formyl methionine peptide, and calcium ionophore. These findings suggest that diatrizoate may induce histamine release via a calcium ionophore-like mechanism, but other effects on cellular function probably account for its ability to inhibit basophil responsiveness.

Characterization of mononuclear cell-derived histamine release enhancing factor.

Histamine release enhancing factor (HREF) is a product of phytohemagglutinin-stimulated mononuclear cells that substantially augments in vitro IgE-mediated basophil histamine release. The factor is stable at 56 degrees C and has a molecular weight in the 10,000 to 30,000 dalton range. The magnitude of HREF activity produced is dependent on the concentration of mononuclear cells cultured and the final concentration of HREF during basophil challenge. The HREF phenomenon could not be attributed to phytohemagglutinin, alpha- or gamma-interferon, arachidonic acid metabolites, or interleukin-1 or 2. HREF appears to be a unique cytokine of potential importance in the immunology of inflammatory and atopic processes.