Showing papers by "Bernard M. Babior published in 1974"

Defective superoxide production by granulocytes from patients with chronic granulomatous disease.

Abstract: Superoxide-dependent cytochrome c reduction was used to measure Superoxide production by granulocytes from two patients with chronic granulomatous disease, from children of similar age wit...

Biological Defense Mechanisms THE EFFECT OF BACTERIA AND SERUM ON SUPEROXIDE PRODUCTION BY GRANULOCYTES

Abstract: We previously reported that granulocytes are able to produce superoxide (O(2) (-)), a highly reactive compound formed by the one-electron reduction of oxygen. The demonstration of O(2) (-) production was based on the observation that the reduction of extra-cellular cytochrome c by granulocytes was greatly diminished by superoxide dismutase, an enzyme catalyzing the conversion of O(2) (-) to hydrogen peroxide and oxygen. In the present report, studies concerning the effect of bacteria and serum on O(2) (-)-dependent cytochrome c reduction by granulocytes are described.In the absence of bacteria, the O(2) (-)-dependent reduction of extracellular cytochrome c by granulocytes under optimal assay conditions amounted to 9.2+/-2.8 SD nmol/3 x 10(6) cells/20 min. When bacteria (100 organisms/cell) were present, the O(2) (-)-dependent cytochrome c reduction under otherwise similar conditions increased by a factor of nearly four (34.5+/-9.4). There was no effect of albumin or catalase on cytochrome c reduction, and boiled dismutase had only a small effect. Omission of granulocytes or substitution of live cells by cells by cells killed by heat abolished O(2) (-)-dependent cytochrome c reduction. Bacteria killed by autoclaving were almost as effective as live bacteria in stimulating granulocyte O(2) (-) production. Measurements of particle uptake and O(2) uptake by granulocytes indicated that superoxide dismutase did not affect granulocyte metabolism nonspecifically, supporting the conclusion that the diminution of cytochrome c reduction in the presence of dismutase was due to the destruction of O(2) (-) by this enzyme. Stimulation of O(2) (-) production by bacteria was strongly dependent on the presence of serum in the incubation mixture. Serum heated to 56 degrees C for 45 min was as effective as unheated serum in stimulating O(2) (-) production in the presence of bacteria, but boiled serum had no effect. Other experiments suggested that incubation of bacteria with serum resulted in the release of a nonparticulate heat-labile substance capable of stimulating O(2) (-) production in the absence of bacteria. Certain characteristics of the O(2) (-)-dependent cytochrome c reduction by granulocytes were studied, including the dependence of this process on granulocyte, cytochrome c, and bacterial concentrations. In addition, O(2) (-)-dependent cytochrome c reduction was followed as a function of time. A constant rate was found with resting granulocytes. With bacteria the time course was more complex. A well-defined lag was followed by a fairly brief period of extremely vigorous cytochrome c reduction. During this period, the maximum rate of cytochrome c reduction exceeded the rate observed in the absence of bacteria by a factor of 12. The rate then decreased until by 40 min, it had slowed to the rate observed in the absence of bacteria. From the above results, it was concluded that the exposure of the granulocyte to bacteria plus serum initiates a process in which a defined quantity of O(2) (-) is formed in a rapid burst lasting 20-30 min. It is conceivable that the O(2) (-) generated by this process may be involved in the killing of bacteria by the granulocytes.

Kinetics of the attachment of intrinsic factor-bound cobamides to ileal receptors.

Abstract: To determine whether the molecular configuration of vitamin B(12) influences the attachment of intrinsic factor-vitamin B(12) complex to ileal microvillous membrane receptor sites, we have examined the kinetics of uptake of intrinsic factor-bound cyanocobalamin by brush borders and microvillous membranes isolated from guinea pig ileum, and have compared this uptake with that of intrinsic factor alone and with that of intrinsic factor complexed with various analogs of cyanocobalamin. We first studied the kinetics of binding of cyanocobalamin and other cobamides to human gastric intrinsic factor. The binding of cyanocobalamin showed saturation kinetics and, at relatively high concentrations of cyanocobalamin, a Scatchard plot of binding was linear. The dissociation constant for the intrinsic factor-cyanocobalamin complex was 0.066 nM. When the binding of various vitamin B(12) analogs to intrinsic factor was determined by competition experiments, the analogs could be separated into two categories: those with affinities similar to that of cyanocobalamin and those with affinities much lower than that of cyanocobalamin. The affinity of cyanocobalamin for intrinsic factor was not altered by various substitutions at the -CN position, while removal of a single amido group on the corrin ring of substitution of the dimethylbenzimidazole base greatly reduced affinity. Removal of the base totally abolished binding. These findings, confirming those reported by others, are consistent with the concept that the cyanocobalamin molecule fits into a "pocket" in the intrinsic factor molecule, with the nucleotide base facing inward and the -CN side of the planar corrin ring facing outward. We then investigated the attachment of intrinsic factor-bound cyanocobalamin to ileal receptor. Attachment to microvillous membranes showed saturation kinetics with a dissociation constant of 0.25 nM. Attachment was rapid and was 70% complete within 5 min; the second-order rate constant for attachment was 1.3 x 10(6) M(-1) s(-1). The half-time for dissociation of intrinsic factor-bound cyanocobalamin from the ileal receptor was approximately 35 min. Free intrinsic factor inhibited the attachment of intrinsic factor-bound cyanocobalamin, but the rate of attachment of free intrinsic factor was slower than that of intrinsic factor bound to cyanocobalamin. When intrinsic factor was complexed with various analogs of cyanocobalamin, the affinities of these complexes for ileal microvillous membranes were similar to that of intrinsic factor-bound cyanocobalamin. These findings suggest that the molecular configuration of vitamin B(12) is not a major determinant in the interaction between intrinsic factor-bound vitamin B(12) and its ileal receptor site.

Kallikrein-kinin system in postgastrectomy dumping syndrome.

Abstract: The kallikrein-kinin system was studied in 10 postgastrectomy patients, 5 with the dumping syndrome and 5 patients without symptoms. After drinking 220 ml of 45% glucose, none of the asymp...