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Biomedical subjects

D E Hammerschmidt

Publications and source records attributed to D E Hammerschmidt.

At least 91 records · Page 5Linked to original sources
PubMed1983

Fat embolism prophylaxis with corticosteroids. A prospective study in high-risk patients.

The efficacy of corticosteroid treatment in the prophylaxis of the fat embolism syndrome was evaluated in a prospective, randomized, double-blind study of high-risk patients with long-bone fractures. Using a set of objective diagnostic criteria, we saw a significant difference in the incidence of the syndrome between corticosteroid- (0 of 21) and placebo-treated patients (9 of 41) (p less than 0.05). There were no complications related to corticosteroid treatment. No routine laboratory or physical findings reliably predicted the development of the fat embolism syndrome except petechial rash, which occurred only in 5 placebo-treated patients who developed the syndrome. Complement activation was present in all patients studied who had the syndrome (5 of 27) but also in many patients who did not meet our diagnostic criteria, suggesting a multifactorial cause. These data support the prophylactic value of corticosteroid treatment in patients at high risk for the fat embolism syndrome, particularly if several unfavorable predictors are present.

Adolescent↗
PubMed1983

Augmentation by platelets of granulocyte aggregation in response to chemotaxins: studies utilizing an improved cell preparation technique.

Considerable evidence exists to suggest roles for both platelets and granulocytes (PMNs) in pulmonary injury in shock. While believing that the major contributions of the two cell types are sequential, in vitro observations suggested that direct interactions between granulocytes and platelets might also amplify tissue damage. Using isotonic Percoll density gradients to isolate PMNs, we therefore studied the effect of deliberate platelet contamination on PMN aggregation. PMN aggregation in response to N-formyl-met-leu-phe or activated complement was enhanced by the presence of 1 platelet/PMN, an effect that became maximal at 16 platelets/PMN (p less than 0.01); large mixed aggregates were formed. Lysed, aspirinated, and indomethacin-treated platelets retained their augmentative capacity, as did platelets washed by gel filtration. The effect was not mimicked by the addition of histamine or serotonin to PMN preparations. None of these platelet preparations augmented lysosomal enzyme release. We conclude that platelets augment PMN aggregation, both by forming giant mixed PMN/platelet aggregates and also by producing a labile augmentative substance, the production of which may be independent of thromboxane synthesis. We propose that direct as well as sequential platelet/PMN interactions may be important in tissue injury in shock.

Blood Platelets↗
PubMed1982

Anisodamine inhibits thromboxane synthesis, granulocyte aggregation, and platelet aggregation. A possible mechanism for its efficacy in bacteremic shock.

Anisodamine hydrochloride is a vasoactive drug produced in the People's Republic of China that appears efficacious in clinical and experimental bacteremic shock, and about whose mode of action little is known. Suspecting that the drug might work by inhibition of platelet or granulocyte aggregation, or both, we tested it in these systems. Anisodamine proved a modest inhibitor of granulocyte aggregation and a powerful inhibitor of platelet aggregation; thromboxane synthesis was inhibited in anisodamine-treated platelets, further suggesting that the biochemical mode of action might be inhibition of cyclo-oxygenase or thromboxane synthetase.

Animals↗
PubMed1982

Synergy among agents inhibiting granulocyte aggregation.

Recent evidence suggests complement (C) -stimulated granulocytes (PMNs) are important in a variety of diseases, including shock and myocardial infarction (MI). Corticosteroids inhibit PMN response to C and show promise in some studies of shock and MI, but their use has not become routine for several reasons. Synergy was sought among agents inhibiting PMN aggregation in vitro in response to activated C: methylprednisolone (MP), with a 50% inhibitory dose (AD50) of 0.6 mg/ml; ibuprofen (IBU), with AD50 of 1.0 mg/ml, and betahistine (BH), with AD50 of 1.6 mg/ml. Simultaneous use of all three agents produced 3.4-fold synergy; 3-fold synergy obtained between IBU + MP and IBU + BH, while 1.5-fold synergy was noted between MP + BH. Further, MP and IBU were at least additive in inhibiting .O2- generation by FMLP-stimulated PMNs and in blocking directed migration. In a preliminary in vivo test of this finding, cats were given MP and IBU--in known individually ineffective doses--immediately prior to coronary artery ligation. Neither MP nor the low dose of IBU chosen limited the size of the resultant MI, while both agents together reduced MI size by 42%. Synergy among these agents suggests that they inhibit PMN function of distinct cellular mechanisms (as yet not elucidated). Further, early in vivo results encourage speculation that such synergy might ultimately be exploited clinically, although such speculation must presently be regarded as preliminary.

Betahistine↗
PubMed1982

Influence of dietary omega-3 fatty acids on granulocyte function.

Manipulation of dietary fatty acid content has been shown to influence platelet aggregation responses. Because granulocytes and platelets interact in a variety of biologic systems, we wondered whether a similar effect might be observed on granulocytes. Granulocyte function was therefore studied in three donors prior to and after three weeks upon a diet supplemented with large amounts of eicosapentaenoic acid. The previously reported attenuation of platelet aggregation was observed, but no effect was seen on granulocyte aggregation, chemotaxis, or superoxide production. Although several other explanations are possible, we suggest that the most likely explanation for this dichotomy is that granulocyte aggregation and chemotaxis are not centrally dependent upon production of thromboxane A.

Adult↗
PubMed1982

Role of peptidoglycan from Staphylococcus aureus in leukopenia, thrombocytopenia, and complement activation associated with bacteremia.

The role of the major cell wall components of Staphylococcus aureus in the leukopenia, thrombocytopenia, and complement activation associated with S. aureus bacteremia was studied in a guinea pig model. Formalin-killed S. aureus strains HSmR, 52A5, Cowan I, and Cowan EMS and purified peptidoglycan were used. Normal animals given peptidoglycan developed early (5-min) leukopenia, thrombocytopenia, and depletion of C3-C9 hemolytic activity similar to values in animals given killed S. aureus organisms and C4-deficient animals challenged with peptidoglycan. Cobra venom factor-treated animals challenged with peptidoglycan did not develop early leukopenia and thrombocytopenia, but all animal groups persistently had late (greater than 1-hr) leukopenia and thrombocytopenia. This observation suggests that peptidoglycan may play a major role in the early leukopenia and thrombocytopenia associated with S. aureus bacteremia in the guinea pig and that these effects can be mediated by activation of the alternative complement pathway alone. Peptidoglycan also causes a late leukopenia and thrombocytopenia which may occur independently of complement activation.

Animals↗
PubMed1982

Therapeutic ramifications of the interaction of complement, granulocytes, and platelets in the production of acute lung injury.

Evidence is reviewed that activation of complement through its ability to cause adhesion of granulocytes to the pulmonary endothelium (margination) and aggregation and embolization of these cells to the lung microvasculature is an important cause of pulmonary injury. Agents capable of diminishing such stimulated adhesiveness might be rational therapeutic adjuncts in vascular-damaging syndromes and are being investigated. To date, corticosteroids, such as methylprednisolone (in enormous doses), and certain nonsteroidal anti-inflammatory drugs, such as ibuprofen, have been shown to diminish granulocyte stickiness in vitro and diminish complement-mediated tissue damage in vivo. Moreover, platelets amplify complement/granulocyte-induced endothelial damage by releasing serotonin, which, in turn, potentiates granulocyte adhesion to endothelium. This potentiation is abrogated by the serotonin antagonists imiprimine and methysergide. Since these diverse agents inhibit granulocyte-adhesion phenomena by different mechanisms, they might predictably be synergistic in their beneficial effect. This prediction is validated for methylprednisolone and ibuprofen, for which we report a threefold synergism in preventing complement-mediated granulocyte aggregation in vitro. Preliminary studies indicate utility of this synergism in vivo as well, in that the degree of myocardial infarction [a complement-activating phenomenon) is diminished in coronary-ligated animals in which rather small doses of the two drugs administered together.

Adrenal Cortex Hormones↗
PubMed1982

Activation of plasma complement by perfluorocarbon artificial blood: probable mechanism of adverse pulmonary reactions in treated patients and rationale for corticosteroids prophylaxis.

Perfluorocarbons have shown promise as clinical blood substitutes. Although early experience in Japan with one such product--Fluosol-DA--has been uncomplicated, we observed an adverse pulmonary reaction in the first American patient to receive it and know of similar reactions in two other Americans so treated. Postulating that activation of plasma complement (C) by the perfluorocarbon emulsion might have caused the reaction, we tested the product to determine if it is an activator of complement. Incubation of Fluosol with plasma led to C3 conversion, decrement in CH50, and generation of C5a-related PMN aggregating activity; EDTA prevented such activation, while EGTA did not, suggesting that it proceeded via the alternative C pathway. Infusion of Fluosol into rabbits produced hypoxemia, neutropenia, thrombocytopenia, and pulmonary leukostasis, mimicking abnormalities previously demonstrated in rabbits receiving infusions of zymosan-activated plasma C. These deleterious responses to Fluosol were diminished by premedicating rabbits with corticosteroids (which had seemed to benefit when used empirically in our patient). In vitro and in vivo, Fluosol's effects were reproduced by Pluronic F-68, the nonionic detergent used to maintain the emulsion stability of Fluosol-DA. We conclude that adverse reactions to Fluosol are probably mediated by C activation and that steroid premedication may prevent them in susceptible patients.

Adrenal Cortex Hormones↗
PubMed1981

Corticosteroids block binding of chemotactic peptide to its receptor on granulocytes and cause disaggregation of granulocyte aggregates in vitro.

Inhibition of complement-mediated granulocyte aggregation has recently been proposed as a mechanism of action of high-dose corticosteroids in shock states. Postulating that such inhibition might be effected through alteration of receptors function, we examined the effect of methylprednisolone (MP), hydrocortisone (HC), and dexamethasone (DEX) on the extent and kinetics of binding of the synthetic chemotaxin f-methionine-leucine-phenylalanine (FMLP) to its specific receptor on the granulocyte surface. Dose-dependent inhibition of binding was observed at corticosteroid concentrations paralleling plasma levels achieved with 30 mg/kg intravenous bolus therapy; the order of potency was MP greater than HC greater than DEX. Receptor number was unaffected by steroid exposure, but the steroids effected a decrease in association rate constant for the FMLP-receptor interaction (35% of N for 0.2 mg/ml MP), leading to decreased receptor-ligand affinity. Dissociation kinetics, as examined by cold-chase experiments, were unaltered by the corticosteroids. Furthermore, in addition to the inhibition of aggregation previously reported, aggregated granulocytes were found to disaggregate upon addition of corticosteroids; the order of potency was again MP greater than HC greater than DEX, with an MP concentration of approximately 2-3 mg/ml required to effect complete disaggregation. We conclude that corticosteroids can displace FMLP from the granulocyte surface by slowing association while allowing dissociation to proceed; altered kinetics of receptor-FMLP interaction may explain both the inhibition of granulocyte aggregation and granulocyte disaggregation. If these observations also hold for physiologic stimuli (such as C5adesarginine, which behaves similarly with respect to aggregation, inhibition, and disaggregation), such kinetic changes may be important in the clinical effects of very high-dose corticosteroids such as are administered in shock.

Adrenal Cortex Hormones↗
PubMed1981

Cholesterol and atheroma lipids activate complement and stimulate granulocytes. A possible mechanism for amplification of ischemic injury in atherosclerotic states.

Previous studies in experimental myocardial infarction have suggested that PMNs and plasma C might interact to intensify ischemic injury. From the finding of large amounts of activated C (specifically C5a) in the plasma of a patient with severe, ulcerating atherosclerosis and the cholesterol embolization syndrome, we postulated that crystalline cholesterol might activate C and thereby amplify infarctive tissue damage. On simple incubation, crystalline cholesterol--as well as lipids from atheromata--activated plasma C; such plasma then potently aggregated normal PMNs and provoked them to damage cultured endothelial cells in vitro. The active principle in cholesterol-incubated plasma was of molecular weight and antigenicity consistent with C5a (or C5a[desarginine]). Optimal activation required the presence of Ig and an intact classical C pathway. Exposure of plasma to crystalline cholesterol by ulceration of, or hemorrhage into, atherosclerotic plaques might therefore activate C in vivo, promoting further ischemic damage by causing leukostatic-leukoembolic compromise of small vessels downstream from the site of activation.

Arteriosclerosis↗
PubMed1981

Complement activation and neutropenia occurring during cardiopulmonary bypass.

Complement activation and pulmonary leukostasis with neutropenia occur in hemodialysis and filtration leukapheresis, with attendant pulmonary dysfunction. Wondering whether similar phenomena might attend cardiopulmonary bypass (CPB), we studied 34 patients undergoing coronary artery bypass operations. As in the other extracorporeal circulation systems, neutropenia (mean 44.7% +/- 4.3% SEM of prebypass PMN count) occurred during the first half hour of bypass and then a rebound neutrophilia followed. CH50 and C3H50 fell 22% to 25% (p for CH50 less than 0.01) during bypass, but C3 conversion and C5a were not demonstrable in patient plasmas. Nonetheless, polymorphonuclear neutrophils (PMNs) harvested late in bypass showed low adherence to nylon and selective chemotactic and aggregative insensitivity to C5a--functional aberrations which are seen after exposure to activated complement. Furthermore, smaller infusions of activated complement into animals produced neutropenia than were required to achieve a detectable [C5a] in the plasma. We conclude that neutropenia during CPB probably results from complement activation below the threshold of detection; complement-stimulated PMNs deserve study as possible mediators of tissue injury occurring during CPB.

Agranulocytosis↗
PubMed1981

Rapid in vivo clearance of C5ades arg: a possible protective mechanism against complement-mediated tissue injury.

C5ades arg is an important mediator of the tissue injury associated with intravascular complement activation and exerts its effects by causing granulocyte aggregation, leukoembolism, and oxidative damage to endothelial cells. We have now investigated some of the mechanisms responsible for deactivation of this potent complement fragment by studying the clearance of C5ades arg from the plasma of New Zealand white rabbits in vivo. Quantitative aggregation of human granulocytes was used as a bioassay for rabbit C5ades arg. After a bolus intravenous infusion of activated autologous plasma complement, athe plasma C5ades arg content peaked within 60 sec and was cleared rapidly and exponentially, with a mean half-life of 3.0 +/- 0.6 (S.E.M.) min. In neutropenic animals the half-life of C5ades arg was prolonged by 57% +/- 22 and splenectomy, but not hepatectomy, also significantly lengthened the half-life by 48% +/- 18. The most striking delay in C5ades arg clearance was induced by inhibition of endogenous proteases with EACA and aprotinin, which prolonged the half-life by 87% +/- 4 and 94% +/- 12, respectively. These data demonstrate that like other complement fragments such as C3a, C5ades arg has a very brief functional half-life in experimental animals and that although other mechanisms may be operative, endogenous proteases, circulating granulocytes, and the spleen may be important in deactivating this biologically important complement fragment. Impairment of these and other clearance mechanisms could lead to prolonged and excessive complement activation and subsequent exaggerated tissue injury.

Agranulocytosis↗