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Biomedical subjects

E C Jong

Publications and source records attributed to E C Jong.

27 records · Page 2Linked to original sources
PubMed1981

Mast cell-mediated tumor-cell cytotoxicity. Role of the peroxidase system.

Mast cells, when supplemented with H2O2 and iodide, are cytotoxic to mammalian tumor cells as determined by 51Cr release, and transmission and scanning electron microscopy. H2O2 at the concentration employed (10(-4) M) initiates mast cell degranulation, and mast cell granules (MCG), which contain a small amount of endogenous peroxidase activity, are toxic to tumor cells when combined with H2O2 and iodide. This toxicity is greatly increased by binding eosinophil peroxidase (EPO) to the MCG surface. Each component of the mast cell, MCG, or MCG-EPO system was required and toxicity was inhibited by the addition of the hemeprotein inhibitors azide or aminotriazole, which is compatible with a requirement for peroxidase in the cytotoxic reaction. A sequence of reactions is proposed in which mast cells, stimulated to release their granules by H2O2 generated by adjacent phagocytes, react with H2O2 and a halide to damage tumor cells. EPO release from eosinophils may contribute to this sequence of reactions, both by stimulation of H2O2-induced mast cell secretion and by combination with MCG to form a complex with augmented tumoricidal activity. These rections may play a role in the host defense against neoplasms.

Animals↗
PubMed1981

Peroxidase-mediated toxicity to schistosomula of Schistosoma mansoni.

Guinea pig eosinophil peroxidase (EPO) was capable of killing schistosomula of Schistosoma mansoni in vitro when combined with hydrogen peroxide and a halide. Killing was measured by 51Cr release, by microscopic evaluation of viability, and by reinfection experiments in mice. Parasite killing was dependent on each component of the EPO-H2O2-halide system, was completely inhibited by catalase and azide, and was partially inhibited by cyanide. The EPO-mediated system required 10(-4) M H2O2 and 10(-4) M iodide at pH 7.0, and the schistosomula were killed with exposure to this system of less than 30 min at 37 degrees C. At pH 6.0, the EPO-mediated system showed significant cidal activity with 10(-6) M iodide. Canine neutrophil peroxidase (myeloperoxidase [MPO]) was also able to kill schistosomula in vitro in the presence of 10(-4) M H2O2 and 10(-4) iodide at pH 7.0 and pH 6.0. Physiologic concentrations of chloride (0.1 M) could substitute for iodide at pH 7.0 and pH 6.0 as the halide cofactor; however, at pH 7.0, a higher concentration of enzyme was required. These findings with isolated enzyme systems are compatible with a role for peroxidase in the host defense against schistosomula.

Animals↗
PubMed1980

Bactericidal activity of eosinophil peroxidase.

A partially purified preparation of guinea pig eosinophil peroxidase was found to be bactericidal when combined with H2O2 and either iodide, bromide, chloride, or thiocyanate ions. The EPO-H2O2-halide bactericidal system had an acid pH optimum and was inhibited by the proteins albumin and gelatin and by the hemeprotein inhibitors azide, cyanide, and aminotriazole. When the EPO concentration of the reaction mixture was lowered, the bactericidal effect at pH 7.0 was lost first with chloride, then with bromide, and finally with iodide as the halide. Activity with physiologic concentrations of chloride was favored by a relatively high EPO level, a decrease in pH below neutrality and an absence of extraneous protein. These findings are discussed in relation to the potential role of the peroxidase system in the intracellular and extracellular toxic reactions of eosinophils.

Animals↗
PubMed1980

Binding of eosinophil peroxidase to mast cell granules with retention of peroxidatic activity.

Eosinophil peroxidase (EPO) and to a lesser degree neutrophil peroxidase (myeloperoxidase, MPO) bound tightly to mast cell granules (MCG), particularly when the latter were depleted of histamine by suspension in physiologic salt solutions. The bound EPO was localized on the surface of the granule, and its dissociation required salt concentrations of high enough ionic strength (greater than 0.75 M) to solubilize the MCG matrix. Elution of MPO from the complex occurred at a lower salt concentration. The MCG/EPO complex retained the capacity of the isolated EPO to catalyze the iodination reaction when supplemented with iodide, H2O2, and a protein acceptor and to kill microorganisms when supplemented with H2O2 and a halide (iodide, chloride). Indeed, the MCG/EPO complex had significantly greater iodinating and bactericidal activity than the free enzyme when standardized to equal guaiacol units of peroxidase activity. Thus, in areas of inflammation where mast cells and phagocytic leukocytes coexist, there is the potential for the formation of active complexes extracellularly between mast cell granules and molecules such as EPO (or MPO) that can affect the inflammatory response.

Animals↗
PubMed1975

Studies on bacteriophages of Propionibacterium acnes.

With the help of adaptation experiments, 61 phage preparations out of 36 Propionibacterium acnes bacteriophages (32 isolated by us and 4 sent from abroad) were established. On the basis of their stability, spectrum of activity, and virulence, 13 phages were selected for phagetyping. 58 well-classified P. acnes strains were grouped into 7 phage-types. 7 strains of P. granulosum, two strains of P. avidum, and one yet ungroupable microserophilic propionibacterium strain were resistant to all 61 phages, even when tested in 100 X RTD. A combination of phagetyping with biotyping resulted in data especially useful for the differentiation of P. acnes.

Bacteriophage Typing↗
PubMedDate not supplied

Paragonimiasis: diagnosis and the use of praziquantel in treatment.

Paragonimiasis was diagnosed in eight patients: five with sputum specimens positive for characteristic ova and three with only stool specimens positive for ova. Clinical symptoms, roentgenograms and serologic findings appeared to correlate with severity of disease. All eight patients were treated with praziquantel (oral dose, 75 mg/kg of body weight daily for two consecutive days). Of seven patients who completed the treatment, six had ova-negative sputum and stool specimens by day 90; the seventh patient's specimens became ova negative by day 120. The eighth patient, who had failed to respond to prior treatment with bithionol, could not tolerate the daily dosage of 75 mg/kg because of nausea. Although he received the same total dose (150 mg/kg) over four days his specimens remained ova positive on day 90. Adverse effects included nausea (two patients), headache (one patient), and urticaria (two), the last effect possibly secondary to release of antigen from drug-damaged parasites. A review of the epidemiology, clinical presentation, and treatment of pulmonary paragonimiasis is presented.

Adolescent↗