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Biomedical subjects

B M Babior

Publications and source records attributed to B M Babior.

At least 145 records · Page 8Linked to original sources
PubMed1979

Unique characteristics of superoxide production by human eosinophils in eosinophilic states.

Eosinophils from patients with peripheral blood eosinophilia and human neutrophils from normal subjects and patients with neutrophilia produced superoxide anion (O2-) in vitro at similar rates in the absence of stimulation and exhibited comparably increased rates of O2- production during the initial 1 h of incubation with opsonized zymosan. In the presence of opsonized zymosan, the rate of O2- production by eosinophils was constantly high for 3 h, whereas the rate of production by neutrophils fell by more than 65% after 1 h. Consequently, the amount of superoxide produced by phagocytizing leukocytes was twofold higher for eosinophils than for neutrophils at 3 h. O2- production by cell-free sonicates of zymosan-stimulated eosinophils and neutrophils exhibited the same preference for NADPH over NADH. One mM sodium azide significantly decreased the generation of O2- by phagocytizing eosinophils, but lacked an effect on neutrophils. the prolonged release of O2- by eosinophils engaged in phagocytosis may contribute both to their unique microbicidal profile and to the capacity of eosinophils to injure host tissues in some eosinophilic syndromes.

Eosinophilia↗
PubMed1979

Subcellular localization of the superoxide-forming enzyme in human neutrophils.

The subcellular distribution of the superoxide (O2-)-forming enzyme in human neutrophils was investigated. Cells were activated by phorbolmyristate acetate or by opsonized zymosan, and were then fractionated by zonal-rate sedimentation at two different speeds. At high speed, the specific granules were resolved from the azurophils and the membrane fraction, while at low speed, the azurophil granules could be separated from fast-sedimenting particle aggregates. Under both conditions, the major portion of the O-2--forming activity (60--70% of the total) was found to be associated with the membrane fraction which was characterized by the presence of alkaline phosphatase, alkaline phosphodiesterase I, and acid aryl phosphatase. No significant O-2--forming activity was found in either specific or azurophil granules. Some activity was present in the fastest sedimenting fractions which, as shown by electron microscopy, were heterogeneous and contained aggregated material which included membrane fragments. These fractionation results provide strong additional support for the current view that the activable O-2--forming system is localized in the plasma membrane of human neutrophils.

Cell Fractionation↗
PubMed1979

Fluoride-mediated activation of the respiratory burst in human neutrophils. A reversible process.

Fluoride ion (F-) is an effective activator of the respiratory burst in neutrophils, as indicated by its ability to induce O2- production by these cells. Other halide ions did not activate the burst, Cl-, in particular appeared to antagonize the effect of F- on O2- production. F- stimulated O2- production showed a requirement for Ca++, but was independent of other exogenous cations. Neither phagocytosis nor degranulation were necessary for respiratory burst activation by F-. The effect of F- on the respiratory burst was reversible. Washing the cells after treatment with F-, while they were still producing large amounts of O2-, returned them to the resting state. They could then be stimulated again to produce O2- in amounts equivalent to those originally produced. Our experiments indicated that restimulation did not represent the activation of a population of cells that had not been activated during the initial exposure to F-, nor did it represent serial activation of different subpopulation of the O2- forming enzyme molecules present in a given cell. Rather, our data suggest that the entire population of O2- forming enzyme molecules was activated in a reversible fashion by F-.

Bromides↗
PubMed1979

Neutrophil-mediated antibody-dependent killing of herpes-simplex-virus-infected cells.

The ability of neutrophils to serve as effectors of antibody-dependent cell-mediated cytotoxicity (ADCC) was studied using herpes-simplex-virus-infected (HSV-infected) human embryonic lung cells as targets. Killing of infected cells by neutrophils required HSV-immune serum and did not take place in the presence of nonimmune serum or in the absence of serum. Uninfected cells were not killed. ADCC was evident by 30 min and reached a value of 66% by 4 hr at an effector:target ratio of 100:1. Cells from patients with chronic granulomatous disease were as effective as normal cells, and this indicates that ADCC could be mediated by processes that are independent of the respiratory burst.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1979

Effects of oxygen tension and pH on the respiratory burst of human neutrophils.

The respiratory burst of human neutrophils was measured under conditions of hypoxia and low pH. O2 -- production by neutrophils activated with opsonized zymosan fell slowly as the oxygen concentration declined to 1%, then dropped more sharply, reaching negligible levels at oxygen concentrations less than 0.25%. Production was half maximal at an oxygen concentration of 0.35% (equivalent to approximately 10-microM dissolved oxygen). O2- production by the cell-free O2- -forming system prepared from zymosan-activated neutrophils showed a similar dependence on oxygen concentration. A drop in pH caused decreases in both oxygen consumption and O2-- production by zymosan-treated neutrophils, values at PH 6.0 being 10%--20% of those observed at pH 7.5. Experiments with the cell-free O2-- -forming system suggested that this decline in respiratory burst activity at low pH was due to inefficient activation of the O2-- -forming enzyme under acidic conditions.

Humans↗
PubMed1979

Evidence for production of oxidizing radicals by the particulate O-2-forming system from human neutrophils.

The particulate O-2-forming system from human neutrophils was found to oxidize methional and 2-keto-4-methylthiobutyric acid (KMB) to ethylene, indicating the formation by this system of strongly oxidizing radicals. Conforming this interpretation was the observation that ethylene production was inhibited by the radical scavengers benzoate, ethanol, and mannitol. Ethylene production was also sharply reduced by superoxide dismutase, implicatin O-2 as a precursor of oxidizing radicals. In our system catalase only partially inhibited ethylene generation from either methional or KMB, suggesting that oxidizing radicals are generated at least in part by the reacton of O-2 with compounds other than H2O2. We propose that in neutrophils oxidizing radicals are formed in a reaction between O-2 and a peroxide according to the following equation: O-2 + ROOH leads to RO . + OH- + O2, in which ROOH may be hydrogen peroxide, an alkyl peroxide, or an acyl peroxide (i.e., a peroxy acid).

Butyrates↗
PubMed1978

Solubilization of the O2(-)-forming activity responsible for the respiratory burst in human neutrophils.

On exposure to suitable activating agents, neutrophils sharply alter their oxygen metabolism, showing large increases in oxygen uptake, O2 and H2O2 production, and glucose consumption via the hexose monophosphate shunt. These metabolic alterations, which together are designated the "respiratory burst," are due to the activation of a system which catalyzes the reaction: 2O2 + NADPH leads to 2O2(-) + NADP. This O2(-)-forming system is found in a particulate fraction isolated from neutrophils which had been activated with opsonized zymosan. When these particles were treated with detergent under suitable conditions, the O2(-)-forming activity was released in a form which passed through a membrane filter capable of retaining species of Mr greater than 3000,000. Soluble O2(-)-forming activity was obtained from normal activated neutrophils, but not from normal resting neutrophils or from activated neutrophils obtained from patients with chronic granulomatous disease, an inherited condition in which the respiratory burst is defective. O2(-)production by the soluble system required a reduced pyridine nucleotide as electron donor, and showed a quadratic dependence on the concentration of the solubilized preparation.

Blood Glucose↗
PubMed1978

The mechanism of action of ethanolamine ammonia-lyase, an adenosylcobalamin-dependent enzyme. Reaction of the enzyme.cofactor complex with 2-aminoacetaldehyde.

Ethanolamine ammonia-lyase (EC 4.3.1.7) catalyzes the adenosylcobalamin-dependent deamination of ethanolamine and 2-aminopropanol. Incubation of the enzyme.cofactor complex with 2-aminoacetaldehyde leads to rapid cleavage of the carbon--cobalt bond accompanied by the destruction of the corrinoid portion of the cofactor. During this reaction the adenosyl portion of the cofactor is oxidized to 4',5'-anhydroadenosine, and the aminoacetaldehyde is converted to acetic acid, which remains associated with the enzyme as a noncovalent complex which survives gel filtration. There is no evidence for the alkylation of the corrin metal by the substrate analog. The enzyme.AdoCbl complex is thus able to eliminate an amino group from a substrate analog without the formation of a new alkyl cobalamin in which the analog is a ligand. These observations do not support the participation of what might be termed "substratylcobalamin" as an intermediate in the ammonia migration occurring in reactions catalyzed by ethanolamine ammonia-lyase.

Ammonia-Lyases↗
PubMed1978

Termination of the respiratory burst in human neutrophils.

Recent evidence has suggested that a particulate O(2) (-)-forming system is responsible for the respiratory burst in activated neutrophils. The respiratory burst is normally a transient event, lasting only 30-60 min. To investigate the mechanism by which the burst is terminated, we examined the O(2) (-)-forming activity of neutrophil particles as a function of time in the presence and absence of agents known to affect the function of intact cells. Measurements of the O(2) (-)-forming capacity of the particles against time of exposure of neutrophils to opsonized zymosan, a potent stimulating agent, revealed a rapid fall in activity when exposure was continued beyond 3 min. Exposure to zymosan under conditions in which the myeloperoxidase system was inactive (i.e., in the presence of myeloperoxidase inhibitors, or in the absence of oxygen) resulted in a substantial increase in the initial O(2) (-)-forming activity of particles from the zymosan-treated cells, but did not prevent the sharp fall in activity seen when zymosan exposure exceeded 10 min. The fall in activity was, however, prevented when activation took place in the presence of cytochalasin B (1.5 mug/ml), an agent thought to act largely by paralyzing the neutrophil through an interaction with its microfilament network.We conclude from these findings that the termination of the respiratory burst results at least in part from the inactivation of the particulate O(2) (-)-forming system. This inactivation involves at least two processes which probably act simultaneously. One is the destruction of the system through the action of myeloperoxidase. The other appears to require active cell motility and is independent of oxygen. The current view holds that the O(2) (-)-forming system of the neutrophil is located in the plasma membrane. It may be that the second process involves the internalization and degradation of this membrane-bound system.

Azides↗
PubMed1977

The mechanism of cobalamin-dependent rearrangements.

Adenosylcobalamin-dependent rearrangements are enzyme catalyzed reactions in which a hydrogen atom is transfered from one carbon atom to an adjacent one in exchange for a group X which migrates in the opposite direction. In the hydrogen transfer step, the mechanism of which is reasonably well understood, the cofactor serves as an intermediate hydrogen carrier. The transfer of hydrogen to the cofactor involves homolysis of the carbon-cobalt bond to generate cob(II) alamin and the 5'-deoxyadenos-5'-yl radical, followed by abstraction of a hydrogen atom from the substrate to form 5'-deoxyadenosine and the substrate radical. After migration of group X, the hydrogen atom is returned to the product radical by the reverse of the above reactions to generate the final product and reconstitute the cofactor. In contrast to the transfer of hydrogen, the mechanism of group X migration is poorly understood. Many reactions mechanisms have been proposed on chemical grounds, but there is insufficient biochemical evidence to permit a choice among these propsals. A quantity of negative evidence has accumulated suggesting that group X migration does not involve alkylation of the cobalt of cobalamin by the substrate, but in the absence of firm data supporting an alternative mechanism, even this weak conclusion must be regarded as provisional.

Chemical Phenomena↗
PubMed1977

Inactivation of ethanolamine ammonia-lyase by 5,5'-dithiobis(2-nitrobenzoic acid). Further evidence for the involvement of sulfhydryl groups in adenosylcobalamin-dependent rearrangements.

Treatment of the adenosylcobalamin-requiring enzyme ethanolamine ammonia-lyase (EC 4.3.1.7) with 5,5'-dithiobis(2-nitrobenzoic acid) (Nbs2) discloses three classes of -SH groups: a rapidly reacting class (2 -SH groups/enzyme molecule), a slowly reacting class (6 -SH groups/molecule) and a class which does not react unless the enzyme is denatured (7 -SH groups/molecule (Kaplan, B.H. and Stadtman, E.R. (1968) J. Biol. Chem. 243, 1794)). The enzyme is inactivated by Nbs2 at a rate similar to the rate at which Nbs2 reacts with the slowly reacting class of -SH groups. Inactivation of the enzyme is retarded by adenosylcobalamin but not by ethanolamine. Once inactivated, the enzyme cannot be reactivated with mercaptoethanol. These observations provide further evidence for the importance of -SH groups in catalysis by adenosyl-cobalamin-requiring enzymes.

Ammonia-Lyases↗