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Biomedical subjects

E L Becker

Publications and source records attributed to E L Becker.

At least 127 records · Page 7Linked to original sources
PubMed1979

A possible role of arachidonic acid in human neutrophil aggregation and degranulation.

Chemotactic factors stimulate neutrophils to aggregate and, in the presence of cytochalasin B, to degranulate. Recently, the authors found that arachidonic acid also stimulates human neutrophils to aggregate but does not stimulate cytochalasin-B-treated or untreated cells to degranulate. In this report the authors examined the effect of three blockers of arachidonic acid metabolism on these cellular responses. It was found that the arachidonic acid analog 5,8,11,14-eicosatetraynoic acid and indomethacin, but not aspirin, inhibited no only the arachidonic-acid-induced aggregation response but also the degranulation responses evoked by C5a or a synthetic oligopeptide chemotactic factor. These results suggest that arachidonic acid may be a precursor of bioactive metabolites that stimulate the aggregation and foster the degranulation responses of neutrophils. Thus, these metabolites may be mediators of neutrophil function. Agents that block their formation may thereby inhibit aggregation and degranulation.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1978

The evidence for the existence of chymotrypsin-like esterase activity in the plasma membranes of rabbit neutrophils and the specific chemotactic peptide binding activity of the subcellular fractions.

1. Light- and heavy-plasma membrane fractions have been isolated from rabbit neutrophils and a chymotrypsin-like esterase has been shown to be present in these fractions. 2. The molecular weight of the chymotrypsin-like esterase of rabbit neutrophil plasma membrane was estimated to be about 200 000. 3. About 93% of the chymotrypsin-like esterase of the plasma membranes is esterase 1 and the susceptibility to potential inhibitors was similar in light- and heavy-plasma membrane. 4. Chemotactic peptide, [3H]formyl-norleucyl-leucyl-phenylalanine [3H]formyl-Nle-Leu-Phe) binding by subcellular fractions shows that the highest specific binding was observed in the light-plasma membrane was about 2-fold higher than the heavy-plasma membrane, about 37-fold higher than the nuclear fraction, about 3-fold higher than lysosomal fraction and about 10-fold higher than the microsomal fraction.

Animals↗
PubMed1978

Quantitative comparisons of various biological responses of neutrophils to different active and inactive chemotactic factors.

The effects of chemotactic factors on rabbit neutrophils were evaluated measuring cell migration in modified Boyden chambers and under agarose, in lysosomal enzyme release, leukocyte aggregation, and in vivo neutropenia. Chemotactins employed included the complement-derived C3 and C5 fragments, the bacterial chemotactic factor from culture supernatant fluids of Escherichia coli, and the synthetic chemotactic factors Met-Leu-Phe and formyl-Met-Leu-Phe. A consistent parallelism was found in all the leukocyte responses to a given chemotactic factor. In no instance, with any of the five chemotactic factor preparations, did cells responding in one assay system fail to respond in the four other assay systems, suggesting a common event in all of the cell responses. Boyden chamber chemotaxis was consistently the most sensitive assay; the agarose assay was, in general, less sensitive by a factor of 100 fold. Enzyme release approached, in cell sensitivity to chemotactic factors, that of the Boyden chamber assay. In general, in vitro leukocyte aggregation and in vivo neutropenia were considerably less sensitive assays. Chemotactic factor inactivator (CFI) purified from human serum destroyed in parallel all biological activities of C3 and C5 chemotactic factors but had no effect on the bacterial chemotactic factor and the activities of synthetic chemotactic peptides.

Aminopeptidases↗
PubMed1978

Activation of the rabbit polymorphonuclear leukocyte membrane "Na+, K+"-ATPase by chemotactic factor.

Addition of the synthetic chemotactic factor, formyl-methionyl-leucyl-phenylala-nine (F-Met-Leu-Phe) to medium containing magnesium, sodium, and potassium results in a doubling of the "Na+, K+"-ATPase activity of the plasma membrane fraction from polymophonuclear leukocytes (PMN). This activation is sensitive to ouabain inhibition and is dose dependent, maximal activity occuring at 10(-9)MF-Met-Leu-Phe. Equivalent activation was observed with the nonformylated derivative Met-Leu-Phe at 10(-9)M. The dipeptide, carbobenzoxy-methionylphenylalanine, which acts as an antagonist for F-Met-Leu-Phe, prevents the stimulation of the "Na+, K+"-ATPase by F-Met-Leu-Phe.

Adenosine Triphosphatases↗
PubMed1978

Substances which aggregate neutrophils. Mechanism of action.

Several agents which influence calcium fluxes in neutrophils were tested for their influence on human neutrophil aggregation. Formyl-methionyl-leucyl-phenylalanine, a synthetic chemotactic tripeptide, aggregated the cells. Cytochalasin B and high levels of extracellular calcium or phosphate enhanced this effect; 10(-6) M to 10(-5) M lanthanum inhibited it. In addition, the calcium ionophore A23187 aggregated the cells. Aggregation induced by the chemotactic factor and A23187 required extracellular calcium. These results correlate with the known or postulated ability of chemotactic factors, A23187, calcium, phosphate, lanthanum, and cytochalasin B to enhance or inhibit the influx and intracellular accumulation of the calcium ion. Transmembrane fluxes or intracellular levels of calcium may modulate PMN aggregation. Aggregation induced by the chemotactic tripeptide and A23187 also required extracellular magnesium. Since calcium and magnesium cannot substitute for each other in the aggregation response to the chemotactic factor or A23187, each bivalent cation must play a separate role in PMN aggregation. The role of magnesium is unknown. Since magnesium, unlike calcium, is known to be necessary for PMN adherence to glass, it may play a permissive role in PMN aggregation. Thus, magnesium may foster the formation of cell-cell adhesions. In addition to inhibiting chemotactic factor-induced aggregation at concentrations of 10(-6) M to 10(-5) M, lanthanum, at concentrations of 10(-4) M to 10(-3) M, aggregated the cells. Lanthanum-induced aggregation did not require extracellular calcium or magnesium. This aggregation may result from the formation of intercellular adhesions by the lanthanum ion directly.

Anti-Bacterial Agents↗
PubMed1978

Desensitization of the neutrophil aggregation response to chemotactic factors.

In the presence of Ca2+ and Mg2+, the chemotactic fragment of C5, the synthetic chemotactic oligopeptide formyl-methionyl-leucyl-phenyl-alanine, and the ionophore A23187 aggregated human neutrophils. Aggregation induced by the two chemotactic factors was transient and reversed within 2 to 4 minutes after exposure; aggregation induced by A23187 was sustained and continued to increase over 15 minutes. In the absence of the bivalent cations, none of these three agents aggregated the cells. If bivalent cations were added after cell contact with a chemotactic factor, aggregation was detected after, but not before, addition of the cations. Under these conditions, the magnitude of the aggregation response was sharply reduced: cells preincubated with a chemotactic factor for longer than 2 to 4 minutes aggregated minimally after addition of bivalent cations. Moreover, cells preincubated with a chemotactic factor for 4 minutes, exposed to bivalent cations, and then rechallenged with the same chemotactic factor also showed a minimal aggregation response, ie, the cells were "desensitized" to the original stimulus. However, cells desensitized to one of the chemotactic factors still aggregated prominently when exposed to the other chemotactic factor or to A23187. Cells could not be desensitized to the ionophore A23187. Desensitization of the neutrophil aggregation response closely resembles desensitization of mast cell and leukocyte degranulation. Degranulation and aggregation appear to be closely related cellular responses to immunologic stimuli. Both responses may reflect alterations in surface membrane permeability to bivalent cations and/or changes in surface membrane adhesiveness to other biologic membranes.

Calcium↗
PubMed1978

Organophosphorus inhibition of lysosomal enzyme secretion from polymorphonuclear leucocytes. Evidence of a lack of a requirement for esterase activation.

Previously, di-isopropylphosphorofloridate (DFP) was shown to inhibit the release of lysosomal enzymes induced by chemotactic factors. It was suggested that the inhibition was due to the phosphorylation of a cell bound serine esterase activated by the chemotactic factor. However, as shown here, di-isopropyl methyl phosphate, a nonphosphorylating analogue of DFP, inhibits just as well as DFP, the release of lysozyme and beta glucuronidase from rabbit polymorphonuclear leucocytes induced by chemotactic factor in the presence of cytochalasin B. Similarly, the poorly phosphorylating phenyl ethyl pentylphosphonate and phenyl ethyl phenylpropylphosphonate inhibit enzyme release, induced under the same conditions, as well as or better than the corresponding good phosphorylators, p-nitropheny ethyl pentylphosphonate and p-nitrophenyl ethyl phenylpropylphosphonate. Phenyl ethyl pentylphosphonate inhibits at least as well or probably better than p-nitrophenyl ethyl pentyl phosphonate, the chemotactic factor induced relase of lysozyme from polymorphonuclear leucocytes spread on Millipore filters in the absence of cytochalasin B. We conclude that, under the circumstances tested, there is no evidence that the release of lysosomal enzymes from rabbit peritoneal polymorphonuclear leucocytes induced by chemotactic factor involves the activation of an esterase.

Animals↗
PubMed1977

Transport of sodium, potassium, and calcium across rabbit polymorphonuclear leukocyte membranes. Effect of chemotactic factor.

The transport properties of the rabbit peritoneal polymorphonuclear leukocyte (PMN) plasma membrane to Na+, K+, and Ca2+ have been characterized. The use of a silicone oil centrifugation technique provided a rapid and reliable method for measuring ion fluxes in these cells. Na+ and K+ movements across PMN membranes were found to be rapid. The value for the unifirectional steady-state fluxes (in meq/liter cell X min) were of the order of 3.0 for Na+ and 7.4 for K+. Ouabian inhibited both K+ influx and Na+ efflux, the latter being also dependent on the presence of extracellular potassium. The rate constant (in min-1) for 45Ca influx was found to be .05 and that for 45Ca efflux .04. The synthetic chemotactic factor formyl-methionyl-leucyl-phenylalanine (FMLP) was found to affect the fluxes of Na+, K+, and Ca2+ at concentrations as low as 10(-10)M. FMLP induced a large and rapid increase in the permeability of the PMN plasma membrane to 22Na. Smaller and delayed enhancements of 42K influx and 22Na efflux were also noted. Some evidence that the latter findings are a consequence of the increased 22Na influx is presented. 45Ca influx and efflux were also stimulated by FMLP. In the presence of 0.25 mM extracellular calcium, FMLP induced an increase in the steady-state level of cell-associated 45Ca. In the presence of .01 mM extracellular calcium, however, a transient decrease in the steady-state level of cell-associated 45Ca was induced by FMLP. The curves relating the concentration of FMLP to its effects on cation fluxes are very similar to those found for its enhancement of migration.

Animals↗
PubMed1977

Changes in ionic movements across rabbit polymorphonuclear leukocyte membranes during lysosomal enzyme release. Possible ionic basis for lysosomal enzyme release.

Changes in the movements of Na+, K+, and Ca+2 across rabbit neutrophils under conditions of lysosomal enzyme release have been studied. We have found that in the presence of cytochalasin B, the chemotactic factor formyl methionyl leucyl phenylalanine (FMLP) induces within 30 s large enhancements in the influxes of both 22Na+ and 45Ca+2 and an increase in the cellular pool of exchangeable calcium. The magnitude of the changes induced by cytochalasin B and FMLP exceeds that induced by FMLP or cytochalasin B alone, and cannot be explained on the basis of an additive effect of the two agents. However, these compounds either separately or together produce much smaller enhancements in 45Ca efflux. The divalent cation ionophore A23187 also produces a rapid and large increase in the influxes of both 22Na and 45Ca+2 in the presence and absence of cytochalasin B. We have also found an excellent correlation between calcium influx and lysosomal enzyme release. 42K influx is not significantly affected by any of these compounds. On the other hand, a large and rapid increase of 42K efflux is observed under conditions which give rise to lysosomal enzyme release. A flow diagram of the events that are thought to accompany the stimulation of polymorphonuclear leukocytes (PMNs) by chemotactic or degranulating stimuli is presented.

Calcimycin↗