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Biomedical subjects

C G Cochrane

Publications and source records attributed to C G Cochrane.

At least 145 records · Page 8Linked to original sources
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↗
PubMed1976

Mechanisms for the involvement of high molecular weight kininogen in surface-dependent reactions of Hageman factor.

The mechanisms by which human high molecular weight kininogen (HMKrK) contributes to the surface-dependent activation of the Hageman factor systems have been studied. The ability of various mixtures of purified human Hageman factor (coagulation factor XII), HMrK, prekallikrein, and kaolin to activate coagulation factor XI was determined with factor XIa (activated factor XI) clotting assays. Hageman factor, HMrK and prekallikrein were required for maximal rates of activation of factor XI. A certain optimal mixture of purified Hageman factor, HMrK, prekallikrein, and kaolin gave the same rapid initial rate of activation of purified factor XI as an equivalent aliquot of factor XI-deficient plasma. This suggests that potent, surface-mediated activation of factor XI in plasma is explicable in terms of Hageman factor, HMrK, and prekallikrein. By studying separately some of the surface-dependent reactions involving Hageman factor, it was found that HMrK accelerated by at least an order of magnitude the following reactions: (i) the activation of factor XI by activated Hageman factor; (ii) the activation of prekallikrein by activated Hageman factor; and (iii) the activation of Hageman factor by kallikrein. Stoichiometric rather than catalytic amounts of HMrK gave optimal activation of factor XI. These results are consistent with the hypothesis that HMrK and Hageman factor form a complex on kaolin which renders Hageman factor more susceptible to proteolytic activation by kallikrein and which facilitates the action of activated Hageman factor on its substrate proteins, factor XI and prekallikrein.

Blood Coagulation↗
PubMed1976

The relationship of structure and function in human Hageman factor. The association of enzymatic and binding activities with separate regions of the molecule.

Three regions of the human Hageman factor molecule termed the c, d, and e regions have been defined. Division of the molecule into these three regions is based on the analysis of fragments obtained by enzymatic cleavage during fluid-phase activation. The three regions have the following properties: (a) the c region has a mol wt of 40,000, has the capacity to bind to negatively charged surfaces, and does not have detectable enzymatic activity; (b) the e region possess a mol wt of 28,000 has enzymatic activity, and does not bind to negatively charged surfaces; (c) the d region has a mol wt of 12,000, is located between the c and e fragments but has not been detected as a freely existing polypeptide, and can bind firmly to negatively charged surfaces. The preparation of antibodies specific for the c and e regions is described as well as their use in defining the electrophoretic characteristics of the cde, cd, de, c, and e polypeptide fragments of Hageman factor. Evidence is given showing that the e region, but not the c or d, is released from a negatively charged surface when bound Hageman factor is exposed to proteolytic enzymes or whole plasma and that when this occurs in the presence of normal plasma, the e fragment becomes bound to C1 esterase inhibitor.

Electrophoresis↗
PubMed1975

Mediation systems in bacterial lipopolysaccharide-induced hypotension and disseminated intravascular coagulation. I. The role of complement.

We have studied the role of complement in lipopolysaccharide (LPS)-induced hypotension and disseminated intravascular coagulation (DIC) by comparing the effects of injection of three preparations of LPS from E. Coli 0111:B4, S. minnesota Re595, and S. marcescens. Injections of nonlethal doses of these LPS preparations into normal rabbits produced decreases in mean arterial blood pressure during a 5-h period. When rabbits treated with cobra venom factor (CoF) to deplete C3 were injected with the various LPS preparations, mean arterial pressures fell at a rate and extent essentially identical to that observed in normal rabbits. Rabbits genetically deficient in C6 also demonstrated LPS-induced hypotensive changes. Only minimal, or no changes in plasma C3 levels or serum CH50 values were detected in normal rabbits after LPS injection. Hypotensive changes were also induced in rabbits when complement was rapidly activated by intravenous injection of CoF. In contrast to the hypotension induced by LPS, the fall in arterial pressure associated with the consumption of complement was short lived and required the rapid consumption of considerable amounts of C3. The occurrence of DIC noted in normal rabbits injected with each preparation of LPS was not inhibited in either rabbits treated with cobra factor or in C6-deficient rabbits. The DIC was most pronounced after injection of Re595 and S. marcescens LPS. Injection of the various LPS preparations produced a rapid disappearance of circulating neutrophils and mononuclear cells, which occurred with the same kinetics and to the same extent in normal, CoF-treated, and C6-deficient rabbits. Injection of either Re595 LPS or S. marcescens LPS produced a biphasic disappearance of circulating 51Cr-platelets. In contrast, injection of 0111:B4 LPS affected only slightly the rate of disappearance of 51Cr-platelets. Depletion of C3 by cobra factor treatment had no effect on the disappearance of platelets in animals injected with 0111:B4. In marked contrast cobra factor treatment greatly reduced the initial rapid disappearance of platelets in rabbits injected with either Re595 or S. marcescens LPS, but had no effect in the secondary disappearance phase.

Animals↗
PubMed1975

The initiation of mast cell degranulation: activation at the cell membrane.

The low molecular weight mast cell activator, polymyxin B, has been covalently bound to an insoluble matrix of Sepharose 4B. It has been demonstrated that mast cells in preparations of rat peritoneal cells bind to Sepharose 4B-polymyxin B beads but not to control beads. The bound cells are stimulated to degranulate by this interaction at the cell membrane with the resultant release of biogenic amines.

Animals↗
PubMed1974

Direct evidence for Hageman factor (factor XII) activation by bacterial lipopolysaccharides (endotoxins).

Purified precursor Hageman factor has been demonstrated to bind to soluble bacterial lipopolysaccharide (LPS, endotoxin) isolated from Escherichia coli 0111:B4, and this complex has been shown to have the capacity to convert prekallikrein to its active form. In addition, LPS-activated Hageman factor substantially reduces clotting times in XII-deficient plasma. The capacity to activate Hageman factor has been demonstrated to reside in the lipid A region of the LPS molecule. Activation of Hageman factor by LPS contrasts with fluid-phase activation (e.g., by kallikrein or trypsin) in that no cleavage to lower molecular weight fragments occurs. High concentrations of LPS inhibit the activity of Hageman factor, probably by a direct LPS-Hageman factor interaction.

Animals↗