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Biomedical subjects

C G Cochrane

Publications and source records attributed to C G Cochrane.

At least 19 recordsLinked to original sources
PubMed1992

Absence of G(i) proteins in the Sf9 insect cell. Characterization of the uncoupled recombinant N-formyl peptide receptor.

We investigated the interaction of the N-formyl peptide receptor (NFPR) with G proteins in infected Sf9 insect cells expressing the recombinant NFPR. Recombinant receptor expression of up to 27 pmol/mg protein was achieved in these cells. The receptor was recognized by an antiserum raised against an NFPR carboxyl-terminal peptide, and displayed specific and saturable binding of the formyl peptide ligand fMet-Leu-[3H]Phe. Scatchard analysis of the binding data yielded a dissociation constant of approximately 62 nM, a binding affinity of 60- to 120-fold lower than that of the high affinity sites in neutrophils and in transfected mammalian cell lines expressing the NFPR. That this low binding affinity was due to a lack of receptor coupling to G protein was suggested by the failure of guanine nucleotides to regulate receptor affinity and by the lack of formyl peptide-stimulated GTPase activity in these cells. Furthermore, immunoblotting with an anti-G(i) antibody and ADP-ribosylation experiments indicated that the approximately 40-kDa G(i) alpha subunit, which couples to the NFPR in neutrophils, is not present in Sf9 cell membranes. Thus, the current study provides for the first time evidence that a major G protein is absent in the Sf9 insect cells. Potential applications of the Sf9 system for in vitro reconstitution of the NFPR-G protein interaction are discussed.

Adenosine Diphosphate Ribose↗
PubMed1992

Isolation of a cDNA that encodes a novel granulocyte N-formyl peptide receptor.

A cDNA of 1650 base pairs was isolated by screening an HL-60 granulocyte library with an N-formyl peptide receptor (NFPR) cDNA probe under low stringency conditions. The cDNA encodes a protein of 351 amino acids tentatively named FPR2, with a calculated molecular weight of 39 kDa. Sequence analysis revealed that FPR2 is 69% identical in sequence to the human NFPR and shares extensive homology to several other chemoattractant receptors. FPR2 expressed in transfected cells mediated formyl peptide-stimulated calcium mobilization at micromolar concentrations of ligand. FPR2 messenger is detected in granulocytic HL-60 cells, but not in undifferentiated HL-60 cells. These findings suggest that FPR2 is a novel receptor for formyl peptide ligand and a new member of the chemoattractant receptor gene family.

Amino Acid Sequence↗
PubMed1992

Elevation of tissue kallikrein and kinin in the airways of asthmatic subjects after endobronchial allergen challenge.

Bronchial tissue kallikrein is the major kininogenase activity in the airways of asthmatic subjects. The relationship of IgE-mediated events to its release and/or activation is unknown, however, and is the subject of this report. Seven subjects with mild atopic asthma underwent endobronchial challenge with relevant aeroallergen. Baseline pre-allergen lavage and sequential post-challenge lavages were collected over an approximate 10-minute time course. Individual aliquots were analyzed separately and compared with saline control lavages performed in a separate lobe. In five of the seven subjects, an increase in tissue kallikrein activity, measured by cleavage of the synthetic substrate Val-Leu-Arg-pNA, was identified in the post-challenge lavages. The antigenic identity of the enzymatic activity was confirmed as a tissue kallikrein in each case by immunoblotting. Tissue kallikrein activity was highly correlated with the appearance of immunoreactive histamine and kinin (p = 0.0001). High molecular weight kininogen influx and cleavage was detected in the post-challenge samples by immunoblotting and paralleled the detection of kinin in BAL fluid. Two of the subjects, despite clinical profiles similar to those of the five positive responders, failed to react to endobronchial challenge. Saline control lavages contained detectable kallikrein, kinin, and histamine in two subjects; in each case, however, this was significantly less than in the post-allergen samples. The results demonstrate a close association between immediate type hypersensitivity events in the lower airway and the appearance of active kallikrein, kininogen substrate, and the liberation of kinin.

Adult↗
PubMed1979

Molecular assembly in the contact phase of the Hageman factor system.

Data obtained in the past few years have defined the molecular mechanisms of contact activation of the Hageman factor pathways of plasma, i.e., the kinin-forming, intrinsic clotting and fibrinolytic systems. Involved are four molecules: Hageman factor, high molecular weight (MW) kininogen, prekallikrein and factor XI. High MW kininogen serves as a surface cofactor to assemble prekallikrein or factor XI in proximity to surface-bound Hageman factor. Reciprocal proteolytic activation of Hageman factor and prekallikrein represents an essential step in the rapid activation of the contact phase. Although Hageman factor does undergo cleavage and activation in the absence of prekallikrein or high MW kininogen, the rate is approximately 50 and 100 times slower than when these molecules are present. Once Hageman factor is activated on the surface, it cleaves and activates clotting factor XI. Activated Hageman factor (HFa) exhibits two molecular forms. One of these, alpha HFa, activates prekallikrein and factor XI, and the intrinsic clotting system on the surface. alpha HFa and clotting factor XI remain surface bound. The other form of activated Hageman factor, beta HFa, leaves the surface, going into solution where it readily activates additional prekallikrein but not factor XI. Of perhaps even greater importance, kallikrein rapidly dissociates from the surface. Thus the formation of bradykinin and fibrinolysis is disseminated whereas clotting via the intrinsic system remains localized. Reviewed here is the molecular mechanism of contact activation of the Hageman factor pathways and discussed in the interaction of Hageman factor with the negatively charged surface, prekallikrein, factor XI and high MW kininogen. The multiple forms of activated Hageman factor and their potential biologic significance are also discussed.

Blood Coagulation↗
PubMed1979

Activation of human Hageman factor by a leukocytic protease.

We earlier reported the IgE-mediated release of a basophil kallikrein of anaphylaxis (BK-A) which, like plasma kallikrein, is an arginine esterase and cleaves human plasma kininogen generating immunoreactive kinin. We herein report that, like plasma kallikrein, preparations rich in this basophil protease also activate human Hageman Factor by proteolytic cleavage of the zymogen molecule into light and heavy chains. These fragments of 28,000 and 52,000 daltons are similar in size to those produced during activation of Hageman Factor by plasma kallikrein. Exposure of Hageman Factor (bound to a negatively charged surface) to BK-A led to the proteolytic cleavage of Hageman Factor producing a 28,000 molecular weight fragment (HFa) which is functionally active and capable of activating prekallikrein to kallikrein. We conclude that, during anaphylaxis, basophils may release a protease that is capable of cleaving and activating Hageman Factor, thus providing a mechanism for initiating the in vivo activation of the Hageman Factor dependent systems.

Anaphylaxis↗
PubMed1978

Surface and fluid phase activities of two forms of activated Hageman factor produced during contact activation of plasma.

The ability of the two forms of activated Hageman factor (HFa) produced during contact activation of plasma to activate prekallikrein and factor XI was studied. alpha-HFa, defined as an 80,000 mol wt two-chain enzyme which remains bound to the surface was capable of cleaving surface-bound prekallikrein and factor XI. beta-HFa, a 28,000 mol wt single chain molecule, released from the surface during contact activation was able to cleave prekallikrein but showed no activity on factor XI. Cleavage of prekallikrein by beta-HFa occurred irrespective of whether the substrate was surface-bound or in solution. Cleavage of factor XI occurred only when it was surface bound and only the alpha-form of HFa was capable of this proteolytic action. Factor XI was found to remain bound to the surface while prekallikrein and kallikrein rapidly dissociated from the surface into the supernate. These findings suggest that the initiation of intrinsic coagulation through the activation factor XI is a localized event occurring at the site of contact activation and is the result of the action of alpha-HFa. By contrast, kinin generation and fibrinolysis resulting from the formation of kallikrein can be initiated either at the site of contact activation, by alpha-HFa action, or throughout the plasma, by beta-HFa; further dissemination of these activities is assured by the rapid dissociation of kallikrein itself from the surface.

Blood Coagulation↗
PubMed1978

Mediating systems in inflammatory disease.

This article reviews the mediation systems participating or potentially participating in inflammatory disease, especially in immunologic injury of the glomerulus. Mediator systems are separated into 3 mechanisms: the first involves complement and neutrophils; the second involves systems unrelated to neutrophils and complement components from C3 to C9; and the third involves blood monocytes. Major emphasis is given to an analysis of factors that potentially participate in the second mechanism. These include humoral factors such as the coagulation system and Hageman factor systems and cellular factor such as platelets or cells resident in the glomerulus. Studies on a role of vasoactive amines are presented. The importance of separating neutrophil-dependent and -independent mechanisms in these studies is emphasized. A review of current knowledge of the biochemical mechanisms involved in the Hageman factor system is presented because of the potential role of these components in the development of inflammation.

Animals↗
PubMed1978

Role of complement in lethal bacterial lipopolysaccharide-induced hypotensive and coagulative changes.

The effect of C3 depletion on the multiple pathophysiological changes produced by a lethal dose of Serratia marcescens lipopolysaccharide (LPS) was evaluated. The injection of this LPS into rabbits resulted in biphasic hypotensive changes and thrombocytopenia. These changes were characterized by an acute, transient decrease occurring within minutes after injection followed by a second more gradual decrease beginning 30 to 60 min post-LPS. Prior depletion of C3, with the anticomplementary protein from cobra venom (CoF), did not alter the extent of either the gradual hypotensive and platelet changes or the coagulative and metabolic changes when normal and C3-depleted rabbits were compared. Importantly, the lethal effects of S. marcescens LPS were not reduced by prior depletion of C3. Only the immediate, reversible thrombocytopenia and hypotension were abrogated by C3 depletion.

Animals↗
PubMed1978

The effect of complement depletion on bacterial lipopolysaccharide (LPS)-induced hemodynamic and hematologic changes in the Rhesus monkey.

Lipopolysaccharide (LPS) isolated from Salmonella minnesota R595 or from Escherichia coli 0111:B4 induces hypotension in rhesus monkeys with normal complement levels. This hypotension is accompanied by decreased total peripheral resistance. The depletion of C3 and terminal complement components by prior intraperitoneal administration of the anticomplementary protein cobra factor did not alter the hemodynamic changes which occur following the rapid injection of 5 mg/kg of R595 LPS, the infusion of 500 microgram/kg of R595 LPS, or the injection of 500 microgram/kg of 0111:B4 LPS. We conclude that the LPS-induced hemodynamic changes in the subhuman primate are medicated by pathways which do not require the participation of C3. The kinetics and extent of the neutropenia and thrombocytopenia resulting from the injection of 0111:B4 or R595 LPS were not latered by prior depletion of greater than 95% of the plasma C3.

Animals↗
PubMed1977

Complement-dependent hemodynamic and hematologic changes in the rabbit.

The intravenous injection of the anticomplementary protein from cobra venom, cobra factor (CoF),2 induces decreases in mean arterial blood pressure and circulating platelets in rabbits. The changes are rapidly reversed. Both changes require the presence of C3 and occur in rabbits genetically deficient in the sixth component of complement. The hypotensive effects of CoF were blocked by the histamine H2-receptor antagonist burimamide. An acute C3-dependent change in blood pressure and circulating platelets also was demonstrated following the intravenous injection of S. marcescens endotoxin. However, abrogation of these acute changes by C3 depletion did not alter the extent of a second, prolonged fall in blood pressure and platelets induced by S. marcescens endotoxin occurring after 60--90 min. C3 depletion also did not alter the lethal effects of the S. marcescens endotoxin.

Animals↗
PubMed1977

Role of granulocytes in immune complex-induced tissue injuries.

Tissue injury of many types may be caused by deposited complexes of antigen and antibody. The circumstances under which the complexes form and deposit often determine the location and type of injury observed: If the complex forms in the circulation, deposition may occur in arterial walls and glomeruli, initiating lesions in those tissues. If the complex forms in the synovial tissues or spaces, then the reaction will develop at that point. Any local source of antigen will initiate these lesions once antibody is formed. If the source of antigen persists, antibody-forming cells soon establish themselves locally as they do in the active Arthus reaction, and injury will become chronic. When the antibody formed is capable of activating complement, polymorphonuclear leukocytes (PMNs, neutrophils) will accumulate, leading to release of injurious constituents. Such is the case in acute glomerulonephritis, arteritis, synovitis, and vasculitis. The ability of complement to attract the PMNs has been demonstrated as an in vitro phenomenon and as a clear possibility in vivo. The requirement of PMNs in the development of the lesions has been demonstrated. The process by which PMNs and other cells (platelets, mast cells, basophils, and macrophages) release injurious constituents is of great interest currently. The exocytosis of their cytoplasmic granules constitutes the major mechanism of release and involves a complicated series of events outlined in this review. The constituents of PMNs capable of injuring tissue in various ways is described, from peptides capable of increasing vascular permeability, to enzymes that indirectly bring more PMNs and other cells into the lesion, to proteolytic enzymes that hydrolyze vital structures in the tissues. These agents were most likely designed to rid the host of invaders; but at times they are unfortunately directed against the host's own tissues.

Animals↗
PubMed1977

Role of high-molecular-weight kininogen in surface-binding and activation of coagulation Factor XI and prekallikrein.

In the contact phase of activation of the kinin-forming, intrinsic clotting, and fibrinolytic systems, high-molecular-weight kininogen acts as a cofactor for the activation of Factor XI, prekallikrein, and Hageman factor. One mechanism by which high-molecular-weight kininogen acts as a cofactor has been studied by using 125I-labeled Factor XI and prekallikrein in kaolin-activated normal human plasma and plasmas deficient in high-molecular-weight kininogen and Hageman factor. High-molecular-weight kininogen was found to be essential for normal binding and cleavage of both Factor XI and prekallikrein on the kaolin surface. Hageman factor was essential for cleavage but not for binding of Factor XI and prekallikrein to kaolin. In normal plasma 80% of the activated Factor XI remained surface-bound, whereas 80% of the kallikrein was not surface-bound. These findings are consistent with the hypothesis that, in the initial phase of contact activation, high-molecular-weight kininogen links both Factor XI and prekallikrein to the exposed surface where they are activated by surface-bound activated Hageman factor. Once activated, the Factor XI molecules remain localized at the site of activation, in contrast to the kallikrein molecules which are found largely in the surrounding plasma.

Adult↗
PubMed1977

The binding and cleavage characteristics of human Hageman factor during contact activation. A comparison of normal plasma with plasmas deficient in factor XI, prekallikrein, or high molecular weight kininogen.

The ability of human Hageman factor (coagulation factor XII) to bind to a glass surface and its susceptibility to limited proteolytic cleavage during the contact activation of plasma have been studied using normal human plasma and plasmas genetically deficient in factor XI, prekallikrein, or high molecular weight kininogen (HMWK). When diluted normal plasma containing (125)I-Hageman factor was exposed to a glass surface for varying times, the Hageman factor was found to bind to the surface, and within 5 min became maximally cleaved from its native 80,000 mol wt to yield fragments of 52,000 and 28,000 mol wt. Hageman factor in factor XI-deficient plasma behaved similarly. In prekallikrein-deficient plasma, the binding of Hageman factor to the glass surface occurred at the same rate as in normal plasma but the cleavage was significantly slower, and did not reach maximum until 60 min of incubation. Cleavage of Hageman factor in HMWK-deficient plasma occurred at an even slower rate, with greater than 110 min of incubation required for maximal cleavage, although the rate of binding to the glass was again the same as in normal plasma. Normal rates of cleavage of Hageman factor were observed for the deficient plasmas after reconstitution with purified human prekallikrein or HMWK, respectively. These observations suggest that normal contact activation in plasma is associated with proteolytic activation of surfacebound Hageman factor. The cleavage of the surface-bound Hageman factor molecule responsible for the formation of the 52,000-and 28,000-mol wt fragments occurred at two closely situated sites, one of which was within a disulfide loop. Cleavage at the site external to the disulfide bond resulted in the release from the surface of the 28,000-mol wt fragment. Cleavage at the site within the disulfide loop resulted in the formation of a 28,000-mol wt fragment which remained surface bound, presumably by virtue of the disulfide linkage to the larger fragment.

Blood Coagulation Disorders↗
PubMed1976

Inflammatory cells in solid murine neoplasms. I. Tumor disaggregation and identification of constituent inflammatory cells.

Mechanical and enzymatic methods of disaggregating tumors were studied with the goals of (1) minimizing cell losses while (2) maintaining functional and surface membrane markers needed to objectively identify inflammatory cells (IC)1 in resultant suspensions. Application of the principles and methods described makes accurate estimation of the percentage of each IC type present in neoplasms possible for the first time. Compared to purely mechanical means of disaggregating tumors, all enzyme mixtures tested markedly increased yields of viable cells/g neoplasm. Best results were obtained with a combination of collagenase and a protease of broader substrate range (alpha chymotrypsin, papain, pronase or trypsin). The combination of enzymes that gave the highest yields with the least effect on inflammatory cell markers was trypsin, collagenase and DNAse (TCD). Because mechanical injury appeared to be the greatest single cause of cell loss (the enzymes themselves had little direct effect), potential sources were identified and either eliminated or minimized. With TCD, depending on the tumor system, cell recovery (measured as DNA recovered in cell suspensions) was as high as 50% and yields were as much as 6.9 X 10(8) viable cells/g tumor. Complete disaggregation was not required to obtain representative IC populations from tumor fragments. Neutrophils, eosinophils and mast cells from disaggregated neoplasms were counted in Giemsa stained cytocentrifuge preparations based on their unique morphologic appearances. Macrophages were identified by their capacity to phagocytose zymosan, a function which proved highly resistant to the effect of enzymes. Flourescent microscopic identification of brain associated thymus antigen (BATA) allowed quantification of T lymphocytes, since this marker was virtually unchanged by enzyme exposure. Surface immunoglobulin (Ig) was stripped from B lymphocytes most rapidly by pronase and chymotrypsin, slowly by trypsin and papain, and not at all by collagenase. Ig positive cells therefore could be quantified in suspensions generated by collagenase or very short (20 min) exposure of fragments to trypsin.

Animals↗
PubMed1976

Inflammatory cells in solid murine neoplasms. II. Cell types found throughout the course of Moloney sarcoma regression or progression.

Regressing and progressing Moloney sarcomas, induced in BALB/c mice by the injection of cultured sarcoma cells (MSC)1, were sampled for histologic analysis and then disaggregated using mixtures of trypsin, collagenase and DNAse or collagenase and DNAse alone. The types of inflammatory cells (IC) found in resultant cell suspensions were determined 6, 11, 14 and 18 days post inoculation. Inflammatory infiltrates were composed almost exclusively of three cell types; neutrophils, T lymphocytes and macrophages. The extent to which each was found in tumors was related to the time post inoculation. Neutrophils were part of an early acute inflammatory response seen in both developing regressing and progressing sarcomas. The onset of regression was associated histologically with the appearance within tumors of a mononuclear inflammatory infiltrate. T lymphocytes and macrophages were the principal constituents. A higher percentage of T lymphocytes was recovered at all sampling times from regressing, compared to progressing, sarcomas. During development of the mononuclear inflammatory infiltrate there were relatively more large T cells in regressing, than in progressing tumors, and the percentage of macrophages was higher. Thereafter, the proportion of macrophages in the recovered cell population was approximately the same for both types of tumor. Such equality was more apparent than real, however, since IC were restricted to the peripheries of progressing sarcomas after the acute inflammatory phase, but continued to be found throughout regressing neoplasms. The effective ratio of macrophages and T lymphocytes to tumor cells therefore was much lower in progressing sarcomas than was suggested by percentage figures. The data presented support the concept that T lymphocytes are instrumental in causing the regression of Moloney sarcomas, possibly through interactions with macrophages.

Animals↗