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Biomedical subjects

D E Hammerschmidt

Publications and source records attributed to D E Hammerschmidt.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of multiple quinine-dependent antibodies in a patient with episodic hemolytic uremic syndrome and immune agranulocytosis.

A 23-year-old woman experienced six distinct episodes of severe combined neutropenia and thrombocytopenia. At least one of the episodes was accompanied by hemodialysis-requiring acute renal failure and fragmentation hemolysis (hemolytic uremic syndrome [HUS]). In retrospect, all episodes were probably associated with the ingestion of quinine. Quinine-dependent antibodies to platelets, neutrophils, T lymphocytes, and red blood cells (RBCs) were detected in the patient's serum. By a monoclonal antibody antigen capture assay, the patient's serum contained IgG antibodies, which in the presence, but not absence, of quinine reacted with platelet glycoprotein (GP) complexes Ib/IX and IIb/IIIa, but not Ia/IIa. By immunoprecipitation assay, the serum, after addition of quinine, reacted strongly with an 85-Kd neutrophil membrane protein and weakly with 130- and 60-Kd moieties. Serum adsorbed with RBCs in the presence of quinine continued to react with platelets and neutrophils, and serum that was absorbed with platelets continued to react with neutrophils and RBCs, indicating that the antigenic targets were different on platelets, neutrophils, and RBCs. Since platelets and endothelial cells share some antigens, we tested patient serum for antibodies to human umbilical vein endothelial cells (HUVEC); no quinine-dependent antibodies to HUVEC were detected. However, her quinine-dependent antibodies not only bound to platelets and neutrophils, but also activated neutrophils. Thus, the patient's serum with quinine aggregated neutrophils, but neither agent alone caused activation. Moreover, the patient's serum with quinine (but not without) augmented the adherence of neutrophils to HUVEC. Treatment of the patient's serum with staphylococcal protein A removed the quinine neutrophil aggregation cofactor, suggesting it was due to IgG. In both neutrophil aggregation and adherence assays, decomplementation of the patient's serum markedly blunted its effect. Furthermore, the patient's serum failed to aggregate formalin-inactivated neutrophils, suggesting neutrophil activation, probably by activated complement, was necessary for aggregation and adhesivity to endothelium. We conclude that our patient's neutropenia, thrombocytopenia, lymphopenia, and anemia were due to quinine-dependent antibodies, and that these antibodies recognized epitopes that were different in the three target cell populations. We further suggest that HUS was likely secondary to the activation and adhesion of neutrophils to endothelium.

Adult↗
PubMed1992

Hemolytic anemia in protoporphyria: possible precipitating role of liver failure and photic stress.

Hemolytic anemia is not a common clinical feature in protoporphyria. In this report, we describe two patients in whom we have encountered severe hemolytic anemia. Both individuals had advanced hepatic disease as a complication of their porphyria and were undergoing orthoptic liver transplantation. The onset of hemolysis appeared to be related to the development of liver disease, and in both cases, the operative procedure acutely exacerbated the red cell destructive process. We suggest that liver involvement in protoporphyria may unmask hemolytic anemia, and that red cells in these individuals are hypersensitive to photooxidative stress, such as might occur during a prolonged operative procedure.

Adolescent↗
PubMed1992

Institutional Review Board (IRB) review lacks impact on the readability of consent forms for research.

Consent forms in research are a source of current and retrospective information for the subject, a "prompt" for the person who is obtaining consent, and a documentation of the "informed" consent process and its adequacy. Occasionally, these forms may be administered by inexperienced trainees or ancillary personnel, and thus stand virtually alone. Therefore, the forms must be inherently comprehensible to the subjects. To test whether this is the case, 65 new applications were randomly selected from 13 consecutive IRB agendas, and their consent documents were computer-analyzed (Flesch/Fry scoring) after correction for expected confounding features, such as lists, tables, and polysyllabic proper names and jargon. Mean U.S. school grade for 70% comprehension (Fry score) was 15.03 +/- 0.19 (standard error of the mean), implying readability by 37.4 +/- 1% of the U.S. adult population. In contrast, a consecutive sampling of 21 Ann Landers columns yielded a mean Fry score of 7.67 +/- 0.5 (p < 0.01; readable by 75 +/- 3%). Fifteen Reader's Digest articles yielded a mean Fry score of 9.95 +/- 0.65 (p < 0.01; readable by 59.1 +/- 3%), and 15 "Talk of the Town" columns from The New Yorker averaged a grade level of 13.3 +/- 0.83; p < 0.01; readable by 42.7% +/- 4.8%). No document was improved by more than one grade level by the IRB review process, and most were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Comprehension↗
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↗
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↗
PubMed1979

Chemotaxigenesis by cell surface components of Staphylococcus aureus.

In an attempt to delineate the staphylococcal cell surface components of importance in chemotaxigenesis, we incubated intact Staphylococcus aureus H, crude cell walls, purified cell walls, peptidoglycan, teichoic acid, and cell membranes with human sera. The results reported indicate that both crude cell walls and purified cell walls, as well as peptidoglycan, were potent chemotaxigens. These particles led to the generation in normal human serum of a factor that was chemotactic for human polymorphonuclear leukocytes. Cell wall peptidoglycan and teichoic acid both appeared to play a role in chemotaxigenesis. Kinetic studies employing C2-deficient serum and immunoglobulin-deficient serum revealed that optimal chemotaxigenesis required the presence of an intact classical complement pathway, as well as antibody. Granulocyte aggregometry studies showed that significant levels of C5a were generated in normal serum and that this activated complement component appears to be a major chemotactic factor produced in serum upon interaction with staphylococcal cell wall components.

Cell Membrane↗