Search PubMed⌕ Search

Biomedical subjects

D E Hammerschmidt

Publications and source records attributed to D E Hammerschmidt.

At least 55 records · Page 3Linked to original sources
PubMed1990

Steroids decrease granulocyte membrane fluidity, while phorbol ester increases membrane fluidity. Studies using electron paramagnetic resonance.

High concentrations of corticosteroids inhibit granulocyte responses and disrupt agonist receptor function. Dose-response and time-course considerations make it unlikely that these effects are mediated via the glucocorticoid receptor, a concept further supported by the ability of sex steroids to work similar effects. We postulated that steroids nonspecifically altered granulocyte membrane fluidity, which we measured directly by electron paramagnetic resonance. As predicted, methylprednisolone caused a dose-dependent increase in order parameter (decrease in fluidity) calculated on the basis of EPR spectra, using 5-doxylstearic acid (5-DS) as a probe of resting PMN membranes. This trend was highly significant (P less than 0.001; P at 0.5 mg/ml less than 0.01). Qualitatively similar results (but with different dose-response features) were obtained with conjugated estrogen. Granulocyte agonists (such as PMA) showed an opposite effect, which was not oxidatively mediated and which was steroid-inhibitable. 16-DS showed less prominent effects, suggesting that the membrane leaflets were more strongly affected than was the deep region of the membrane. Ibuprofen, which has similar effects to those of methylprednisolone on PMN aggregation and receptor function, caused a fluidizing rather than a stiffening of the membrane; this surprising result may indicate that there is a critical range of membrane fluidity for normal function, outside of which--in either direction--agonist receptor dysfunction occurs. We conclude that the immediate effects of very high doses of steroids are probably not mediated by corticoid receptors; instead, they may be due to changes in membrane fluidity.

Electron Spin Resonance Spectroscopy↗
PubMed1989

Inhibition by halothane, but not by isoflurane, of oxidative response to opsonized zymosan in whole blood.

In an attempt to clarify some apparent discrepancies in reports of the effects of anesthetic agents upon granulocyte function, we studied the effects of halothane and isoflurane, using techniques that allowed us to perform the assays in and in sealed vials to prevent volatile gas evolution: assay gas concentrations were measured, rather than inferred. Chemiluminescence, superoxide production, and hydrogen peroxide production were assessed after presentation of opsonized zymosan as a phagocytic stimulus. Incubation with halothane led to a highly statistically significant dose-related inhibition of chemiluminescence (maximum 66%), H2O2 production (67%) and .O2- production (61%), within the concentration range observed in blood from patients undergoing general anesthesia. In contrast, the presence of isoflurane led to no statistically significant changes in any of the functions measured. Cells harvested from patients undergoing elective halothane anesthesia showed the same functional inhibition, but for quantitative differences likely due to the inability to control for dilution effects in clinical samples. It has been suggested that halothane anesthesia may be associated with excess mortality in septic patients; although the results we report are readily reversible, their presence during a prolonged anesthesia could be harmful in a patient who is not immunologically normal and/or who is already infected. Careful clinical trials will be necessary to determine if isoflurane is a superior agent in this context.

Blood↗
PubMed1989

Permeability studies in a hypovolemic traumatic shock model: comparison of Ringer's lactate and albumin as volume replacement fluids.

In order to shed light on the controversy surrounding the choice of resuscitative fluids in shock, we used a canine model which we feel to be a superior mimic of human traumatic shock, combining hemorrhage (to a mean arterial pressure of 50 mmHg), fracture of both femora, and soft tissue crush. After 90 min, animals were resuscitated by reinfusion of shed blood, supplemented by 5% albumin (n = 8) or lactated Ringer's solution (n = 8). Plasma colloid osmotic pressure (COP), transcapillary escape rate for albumin (TER), total lung water and extravascular lung water (EVLW) were measured. COP fell in both groups, but remained above 9 mmHg in the albumin recipients, while falling below 7 in those receiving crystalloid (P less than 0.05). Overall, the increase in EVLW averaged 20%; albumin recipients fared better (9.7%) than Ringer's recipients (31.1%), but wide inter-animal variation precluded statistical significance (P = 0.095). TER rose 30% per hour, without difference between groups. Quality of resuscitation (achieved blood pressure and cardiac output) was somewhat better in the albumin group. We conclude that this model allows study of the early microvascular leakage seen in shock; within the time-frame studied (maximum 4.5 h following shock), colloid and crystalloid resuscitation were approximately equivalent.

Albumins↗
PubMed1988

Development of a simple radioimmunoassay for human C3a.

A radioimmunoassay was devised for the human complement cleavage product, C3a, using charcoal separation and selective precipitation of interfering substances. When compared with the commercially available immunoassay now marketed, the assay reported here was somewhat simpler to perform; furthermore, it overcame delivery and availability problems in Europe. The assay showed a mean recovery of 87% of known amounts of C3a or C3adesarginine and had a sensitivity of 32 ng C3a per milliliter of plasma; coefficients of variance were comparable to other radioimmunoassays in common use. Using this assay in a first clinical application, we were able to document a small but statistically significant rise in [C3a] during cardiopulmonary bypass.

Anaphylatoxins↗
PubMed1988

Inhibition of granulocyte function by steroids is not limited to corticoids. Studies with sex steroids.

Noting that corticosteroid doses required for protection in shock models exceeded those required to saturate glucocorticoid receptors in mammalian cells, we postulated a nonspecific physicochemical effect of steroids upon the cell membrane, and therefore tested three noncorticoid steroids for their effects on granulocyte function. All three (conjugated equine estrogen, a synthetic progestogen, and a synthetic androgen) behaved in manner analogous to corticoids at similar concentrations, inhibiting granulocyte aggregation, chemotaxis, and chemiluminescence, as well as binding to the granulocytes of the synthetic oligopeptide agonist f-Met-Leu-Phe. Estrogen was further shown to reduce granulocyte membrane fluidity, assessed by electron paramagnetic resonance. We propose that the unique effects of extremely high-dose corticosteroids are not mediated via the glucocorticoid receptor, but result rather from physicochemical effects of the drugs upon the membranes of effector cells.

Adrenal Cortex Hormones↗
PubMed1988

Limitation of complement activation by perfluorocarbon emulsions: superiority of lecithin-emulsified preparations.

A considerable body of evidence suggests that complement and granulocyte activation may be important in the occasional adverse reactions which occur on the administration of perfluorocarbon emulsions to patients. In an attempt to develop an emulsion which was less prone to activate complement than was the first product clinically tested, we devised an in-vitro protocol for the testing of an emulsion's ability to activate complement: emulsions were serially diluted, and were incubated with minimally-heparinized plasmas from each of several donors; the generation of C3a was assessed by commercial immunoassay. In such a system, F-Adamantane emulsions prepared with highly-purified lecithin as the emulsifier were consistently less complement-activating than comparable emulsions prepared with Pluronic F-68 as the emulsifier. Emulsification technique seemed unimportant, and HPLC fractionation of the Pluronics identified no innocuous subfraction. Application of these findings to an animal model is underway, to see if the superiority of lecithin-based emulsions is also evident in vivo.

Adamantane↗
PubMed1988

Pentoxifylline inhibits granulocyte and platelet function, including granulocyte priming by platelet activating factor.

Pentoxifylline has been claimed to work a beneficial effect in arterial insufficiency by improving erythrocyte deformability and thus improving blood flow. A number of observations, including the drug concentrations required to work the red cell effect, suggested that this was not likely to be a complete explanation. We therefore examined the effect of pentoxifylline on several granulocyte and platelet functions. Pentoxifylline inhibited platelet aggregation in response to 4 mumol/L adenosine diphosphate; although statistically significant inhibition was seen at 1 mumol/L pentoxifylline, over 200 mumol/L was required for 50% inhibition. The adherence of unstimulated platelets to cultured endothelial cells was not strongly inhibited by pentoxifylline; however, the additional increment in adherence seen in the presence of thrombin was strongly inhibited (50% attenuative dose [AD50] = 18 mumol/L). Granulocyte aggregation in response to C5a was modestly inhibited (AD30 approximately equal to 8 mumol/L; AD50 greater than 1 mmol/L), and the adherence of unstimulated polymorphonuclear neutrophils (PMNs) to endothelium was uninhibited. The C5a-mediated augmentation of PMN adherence to endothelium was mildly inhibited (AD50 = 240 mumol/L). Inhibition of PMN chemotaxis to N-Formyl-methionyl-leucyl-phenylalanine (FMLP) or C5a (AD50 = 12 mumol/L) and inhibition of superoxide production in response to FMLP-cytochalasin B (AD50 = 24 mumol/L) were seen at more clinically credible concentrations. Perhaps most important, pentoxifylline blocked the ability of platelet activation factor to prime neutrophils for enhanced response to subsequent stimuli (AD50 approximately equal to 8 mumol/L; AD60 = 10 mumol/L when production was the indicator system); in vivo, this could broaden the drug's effect to include functions that it does not inhibit potently in a primary fashion. Although pentoxifylline is known to be a phosphodiesterase inhibitor, and we found it to elevate intracellular cyclic adenosine monophosphate in stimulated PMNs, we found it to be only marginally more potent than theophylline in this regard; therefore, the failure of theophylline to inhibit PMN priming suggests that this enzyme inhibition is not a complete explanation of the pharmacologic action of pentoxifylline. We suggest that the effects of pentoxifylline on platelet and granulocyte function are likely to contribute to the drug's clinical efficacy.

Blood Platelets↗
PubMed1988

Lymphocyte aggregation in response to adrenergic stimulation.

A nonanemic chronic lymphocytic leukemia patient with nearly 500,000 lymphocytes/microL underwent leukapheresis when she presented with CNS symptoms and retinal vascular engorgement. Respiratory distress developed during the cell separator run, which led us to ask whether the procedure could have changed the adhesive properties of her cells. C5a desarginine, N-f-Met-Leu-Phe, adenosine diphosphate, and collagen all failed to aggregate her lymphocytes in vitro, but arachidonic acid, excess free calcium, and 4 mumol/L epinephrine did aggregate the cells. Arachidonate-induced aggregation appeared to be a toxic phenomenon: the ED50 for aggregation was statistically indistinguishable from that for cytotoxicity, and aspirin only mildly blunted the response. In contrast, epinephrine-induced aggregation was not associated with lactic dehydrogenase release or the loss of trypan blue exclusion and was blunted by propranolol; radiopindolol-binding studies confirmed the presence of a beta-adrenergic receptor. There were approximately 3,000 receptors/cell, with no statistically significant difference between normal and chronic lymphocytic leukemia B cells or between B cells and T cells (separated by rosetting techniques). The Kd for the B cells' receptor, however, was less than that for T cells by a factor of ten (P less than .01). We conclude that B cells may aggregate when stimulated and that they--like T cells--have beta-adrenergic receptors. Adrenergically mediated changes in B cell adhesiveness may play a role in regulating lymphocyte traffic; in the rare patient with truly enormous B cell counts, we postulate that they may be an occasional cause of morbidity.

Adenosine Diphosphate↗
PubMed1988

Endogenous and exogenous adenosine inhibit granulocyte aggregation without altering the associated rise in intracellular calcium concentration.

The effects of adenosine, adenosine deaminase (ADA), and an irreversible ADA inhibitor 2'-deoxycoformycin (DCF) on granulocyte aggregation in response to four different stimuli: the synthetic chemotaxin N-formyl-met-leu-phe (FMLP), zymosan-activated plasma (ZAP), the calcium ionophore A23187, and phorbol myristate acetate (PMA) were studied. Adenosine inhibited granulocyte aggregation in response to 10(-7) mol/L FMLP in a dose-dependent fashion; inhibition in the presence of 1 mumol/L adenosine was 25% +/- 3% (SD) and was 50% (the maximal inhibition observed) with 1 mmol/L adenosine. Quantitatively similar results were obtained when ZAP or A23187 was used as the aggregant but the response to PMA was not affected. ADA not only reversed the inhibition due to adenosine but actually augmented the aggregation to FMLP by 118% +/- 9%. Similar results were obtained with ZAP and A23187 but not with PMA. These effects of ADA depended on its enzymatic activity as they could be blocked by preincubation with DCF. Fluorescent measurement of intracellular calcium in fura-2 loaded granulocyte suspensions established that neither adenosine nor ADA affected subsequent FMLP-stimulated calcium responses. Adenosine, therefore, may inhibit granulocyte responsiveness by blocking signal transduction at a point after calcium entry/mobilization but before activation of protein kinase C. Furthermore, the augmentation of responses seen with ADA suggests that endogenous adenosine may be a physiologic autocrine regulator of granulocyte function.

Adenosine↗
PubMed1987

Leukocytes and the risk of ischemic diseases.

Predictive indexes for atherosclerotic risk are imperfect, suggesting that there are predictive factors not commonly considered. Such a factor may be the white blood cell (WBC) count. Epidemiologic studies have shown correlations between the WBC count and the risk of myocardial infarction and stroke. The risk of acute myocardial infarction is approximately four times as great in persons with WBC counts high in the normal range (greater than 9000/microL [9 X 10(9)/L]) as in persons with WBC counts low in the normal range (less than 6000/microL [6 X 10(9)/L]); only 50% to 65% of the excess risk of the high-count individuals is explainable by tobacco smoking (which covaries with WBC count). A high WBC count also predicts greater risk of reinfarction and of in-hospital death. Less rigorously studied, the constitutional neutropenia of Yemenite Jews appears to afford protection against atherosclerotic disease. Among WBC types, the strongest epidemiologic association has been with the neutrophil count. Such a predictive value of WBC count is plausible and satisfying, because WBCs make a major contribution to the rheologic properties of blood; alter adhesive properties under stress--including the stress of ischemia, enhancing their rheologic importance; and participate in endothelial injury, both acutely and chronically, by adhering to endothelium and damaging it with toxic oxygen compounds and proteolytic enzymes. Techniques newly developed or under development may allow us to refine the predictive value of the WBC count by combining it with measures of cell activation and/or activatability.

Blood Vessels↗
PubMed1987

Granulocytes as mediators of tissue injury in shock: therapeutic implications.

In summary, over the last twenty years, we have gained a substantially improved understanding of the ways in which granulocytes can damage host tissues. Most recently, there has been a great deal of interest in the intravascular behavior of granulocytes, and the possibility that such behavior might contribute to complications of extracorporeal circulations, bacteremic infections and shock. These insights give us several ideas about possible therapeutic interventions: corticosteroids or other drugs might be used to blunt granulocyte responsiveness; iron chelation might be used to limit the production of toxic hydroxyl radical; competitive inhibition of oxidant damage might be possible using such simple compounds as methionine; protease inhibitors might blunt endothelial cell delamination. Unfortunately, most of these therapies have been tried, with mixed results. It is likely that in most cases of shock, the damage worked by granulocytes occurs very early, often before the patient is recognized as having shock or being at risk for shock. Therefore, by the time a decision is made to employ one of the above modalities, it may already be too late. Perhaps the greatest opportunities for improving our ability to treat irreversible shock and the shock lung syndrome lie with the early identification of patients at risk for development of the syndrome, so that antigranulocyte therapies can be applied before the damage is done.

Adrenal Cortex Hormones↗
PubMed1986

Effects of ibuprofen on chemotactic peptide-receptor binding and granulocyte response.

Inhibition of complement-mediated granulocyte aggregation has been proposed recently as a mechanism of action of high-dose corticosteroids and ibuprofen in shock states. Such inhibition by corticosteroids may be effected through alteration of receptor function, and we have therefore examined the effect of ibuprofen on the extent and kinetics of binding of the synthetic chemotactic peptide formylmethionine-leucine-phenylalanine (FMLP) to its specific receptor on the granulocyte surface. Dose-dependent inhibition of binding was observed at ibuprofen concentrations paralleling plasma levels achieved with 30 mg/kg intravenous bolus therapy, and also at concentrations achieved with oral therapy. Ibuprofen did not affect the receptor number, but did decrease the association rate constant for the FMLP-receptor interaction (30% of normal for 0.125 mg/ml ibuprofen), leading to a decrease in receptor affinity for ligand. Dissociation kinetics, as determined by cold chase experiments, were unaltered by ibuprofen. We conclude that ibuprofen, like corticosteroids, can slow the rate of association of FMLP with its receptor on the granulocyte surface while allowing dissociation to proceed; altered kinetics of receptor-FMLP interaction may explain the inhibition of granulocyte aggregation. Blockade of granulocyte surface receptors for inflammatory stimuli may be important in the clinical effects of very high-dose corticosteroids and ibuprofen such as are administered in shock; such effects are seen at blood levels of ibuprofen that occur with oral therapy. Similar observations may hold for other physiologic stimuli.

Cell Aggregation↗
PubMed1986

Clinical utility of complement anaphylatoxin assays.

Meaningful quantitation of complement activation is difficult by conventional techniques, because of the dynamic equilibrium status of complement components. Assays for complement-derived split products have been useful adjuncts, but until recently have been cumbersome and only semiquantitative. The recent introduction of superior assay methods, especially immunoassays for the complement derived anaphylatoxins, has enhanced such study by allowing more sensitivity, specificity and reproducibility. Such assays are already being applied to the study of diseases in which complement activation may play a role, as well as to the evaluation of biocompatibility of various prosthetic materials and drugs. 'Beside' clinical utility of the tests is still limited, but may grow rapidly if assays are devised which are capable of more rapid and less expensive performance.

Anaphylatoxins↗
PubMed1986

Corticosteroids reversibly inhibit chemotactic peptide-receptor binding and granulocyte response, yet allow desensitization and receptor down-regulation.

Inhibition of complement-mediated granulocyte aggregation has recently been proposed as a mechanism of action of high-dose corticosteroids in shock states. Such inhibition may be effected through alteration of receptor function. Methylprednisolone inhibits binding of the synthetic chemotaxin f-methionine-leucine-phenylalanine (FMLP) to its surface receptor on granulocytes in a dose-dependent manner by slowing the association rate of the FMLP-receptor interaction without altering receptor number. Because the half-life of high-dose methylprednisolone in vivo is short, we examined the reversibility of its effects on granulocyte aggregation and receptor function; both effects were readily reversed by washing. Furthermore, methylprednisolone, at concentrations that profoundly inhibited the granulocyte aggregation response to FMLP, allowed the occurrence of FMLP-receptor down-regulation and granulocyte desensitization to further stimulation by FMLP. We conclude that methylprednisolone at concentrations that inhibit granulocyte aggregation can slow the rate of the FMLP-receptor interaction while simultaneously allowing receptor down-regulation and granulocyte desensitization to proceed. Transient blockade of granulocyte function with concomitant desensitization and receptor down-regulation may be important in the clinical effects of very high-dose corticosteroids such as are administered in shock and could partially explain how drugs with such short half-lives administered intermittently could exert a beneficial effect in shock states. Similar observations may hold for other physiologic stimuli.

Cell Aggregation↗
PubMed1985

Use of a whole blood substitute, Fluosol-DA 20%, after massive postpartum hemorrhage.

Two patients with severe postpartum hemorrhage refused blood product transfusion for religious reasons. The patients' hemoglobin level had dropped to 3.0% or less after operative intervention, and the cardiac indexes on transfer to the tertiary care center were 8.0 and 7.3 L/minute per m2, respectively. Each received an infusion of Fluosol-DA 20% according to research protocol after obtaining informed written consent. Pulse rates and cardiac outputs dropped after the infusions. They were discharged from the hospital 17 and 15 days later with hemoglobins of 7.0 and 5.1%, respectively. Fluosol-DA 20% may be a useful adjunct for therapy of postpartum hemorrhage in women who refuse blood products for religious reasons.

Adult↗