Biomedical subjects

G B Stefano

Publications and source records attributed to G B Stefano.

At least 109 records · Page 6Linked to original sources

PubMed1997

Biochemical identification and ganglionic localization of leech angiotensin-converting enzymes.

We demonstrate the presence of a membrane and soluble form of leech Theromyzon tessulatum angiotensin-converting enzyme (ACE). Four steps in the purification of this enzyme include gel-permeation, captopril-sepharose affinity and anion-exchange chromatography followed by a reverse-phase HPLC. The peptidyl dipeptidases (of approximately 120 and approximately 100 kDa) are glycosylated enzymes hydrolysing the Phe8-His9 bond of angiotensin I, exhibiting the same specific activity and Km whereas the soluble ACE exhibits a higher catalytic efficiency. This hydrolysis is inhibited by the ACE-specific antagonist captopril. Western blot analysis of a polyclonal antiserum raised against the first 11 amino-acid residues of the membrane ACE and the N-terminal sequence of the soluble molecule also demonstrates the presence of two ACE enzymes. Anti-ACE immunocytochemistry also supports the presence of two forms of ACE. This material is found in neurons and glia. We demonstrate for the first time the cellular localization and biochemical characterization of ACEs in the central nervous system of an invertebrate. Thus, the leech brain may represent a simple model for the study of these enzymes.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1997

Invertebrate proenkephalin: delta opioid binding sites in leech ganglia and immunocytes.

The leech Theromyzon tessulatum and the marine mussel Mytilus edulis immunocytes contain a mammalian-like proenkephalin molecule. The opioid precursor was purified by gel permeation chromatography, anti-Met- and Leu-enkephalin-affinity column separation and then by reversed-phase HPLC. The amino acid sequence analysis, determined by Edman degradation, enzymatic treatments and matrix assisted laser desorption time of flight. The structure of the leech proenkephalin material demonstrates considerable amino acid sequence similarity with amphibian proenkephalin (e.g. 25.4% with Xenopus laevis) but it is smaller, 15 kDa vs. 30 kDa. In contrast, Mytilus proenkephalin is not only larger (26 kDa) but it exhibits a higher sequence identity with guinea pig proenkephalin (50%). Both of the invertebrate materials possess Met-enkephalin and Leu-enkephalin in a ratio of 3:1 for Mytilus and 1:2 in the leech. They also contain Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe sequences that are flanked by dibasic amino acid residues, demonstrating cleavage sites. Furthermore, using sequence comparison with bovine proenkephalin A (209-237), enkelytin (FAEPLPSEEEGESYSKEVPEMEKRYGGFM), an antibacterial peptide is found in the proenkephalin of both animals and it exhibits a 98% sequence identity with mammalian material. Finally, opioid binding experiments demonstrate the presence in leech ganglia and immunocytes of delta1 and delta2 opioid receptor subtypes as also found human and Mytilus immune cells. This report constitutes the first complete biochemical characterization of mammalian proenkephalin in invertebrates, demonstrating its origin in simpler animals.

Amino Acid Sequence↗

PubMed1997

Morphine- and anandamide-stimulated nitric oxide production inhibits presynaptic dopamine release.

Morphine and anandamide stimulate the release of nitric oxide (NO) in diverse tissues. The present study examines the consequences of this action on neurotransmitter release in ganglia from two invertebrates: ventral chain ganglia from the leech Hirudo medicinalis and the pedal ganglion from the mussel Mytilus edulis. In these ganglia, preloaded serotonin (5-HT) and dopamine (DA) can be released by 50 mM KCl. Anandamide, an endogenous cannabinoid substance, suppresses the potassium-stimulated release of [3H]DA (80%), but not 5-HT, in a concentration-dependent manner, from the neural tissues of both. The effect of anandamide can be antagonized by pre-exposing the neural tissues of both animals to SR 141716A, a potent cannabinoid receptor antagonist. Prior treatment of the ganglia with N-omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, significantly diminishes the inhibitory effect of anandamide. Morphine also inhibits [3H]DA release in a naloxone- and L-NAME-sensitive manner. Anandamide and morphine act through separate mechanisms since the respective antagonists show no cross-reactivity. The NO donor, SNAP, depressed the potassium-stimulated release of preloaded [3H]DA, but not 5-HT, in the neural tissues of both animals. D-Ala2-Met5 enkephalinamide (DAMA) also inhibited the potassium-stimulated release of [3H]DA in a naloxone-sensitive process. However, the effect of DAMA was seen in the presence of L-NAME (10(-4) M), indicating that the opioid peptide inhibition of the presynaptic release of DA is not coupled to NO. We postulate that cannabinoids and their endogenous effectors play a prominent role in the regulation of catecholamine release in invertebrates via NO release as is the case for opiate alkaloids.

Animals↗

PubMed1997

Identification and characterization of the leech CNS cannabinoid receptor: coupling to nitric oxide release.

The present study demonstrates that stereoselective binding sites for anandamide, a naturally occurring cannabinoid substance, can be found in leech (Theromyzon tessulatum and Hirudo medicinalis) central nervous system. The anandamide binding site is monophasic and of high affinity exhibiting a Kd of approximately 32 nM with a Bmax of 550 fmol/mg protein in both animals. These sites are highly select as demonstrated by the inability of other types of signaling molecules to displace [3H]anandamide. Furthermore, this binding site is coupled to nitric oxide release. A deduced amino acid sequence (153 residues) analysis from a 480 pb amplified RT-PCR fragment cDNA exhibits a 49.3% and 47.2% sequence identity with human and rat cannabinoid receptors (CB1R), respectively. Thus, the leech cannabinoid receptor may be a G-protein coupled receptor with seven transmembrane domains as in CB1R. Moreover, this sequence exhibits highly conserved regions, particularly in the putative transmembrane domains 1 and 2. The presence of a cannabinoid receptor in these organisms indicates that this signaling system has been conserved during evolution.

Amino Acid Sequence↗

PubMed1997

Human monocyte adhesion is modulated by endothelin B receptor-coupled nitric oxide release.

Human monocytes have the capacity to produce both endothelin 1 (ET-1) and nitric oxide (NO), yet the roles of these mediators in monocyte function remain unclear. The relationship of ET-1 and NO release to monocyte adhesion was explored using peripheral blood monocytes (PBM) and the human monocytic cell lines THP-1 and U937. Specific binding of 125I-labeled ET-1 to THP-1 was abrogated by pretreatment with the endothelin B (ET(B)) receptor antagonist, BQ-788, but not by the endothelin A (ET(A)) receptor antagonist, BQ-123, consistent with predominant ET(B) receptor expression. Direct measurement of NO with an amperometric probe demonstrated the production of nanomolar concentrations of NO by PBM and THP-1 cells upon treatment with ET-1, which was abrogated by BQ-788, but not BQ-123, pretreatment, suggesting functional coupling of ET(B) receptors to NO release. Indeed, the presence of ET(B) receptor mRNA transcripts was detected in THP-1 and is consistent with previous reports that have demonstrated functional coupling of ET(B) receptors to constitutive NO synthase activation. In contrast, U937 cells did not release NO in response to ET-1 treatment, and mRNA transcripts were not detected in these cells, consistent their failure to bind 125I-labeled ET-1, as previously determined. Exposure of PBM to ET-1 markedly reduced the adhesion of these cells to human saphenous vein, whereas PBM adhesion in the presence of BQ-788 was restored to control levels. These data demonstrate that PBM interactions with the vascular wall can be reduced by autocrine production of NO and suggest that ET(B) receptors may attenuate monocyte activity at sites of inflammation.

Cell Adhesion↗

PubMed1997

Cell behavior and signal molecule involvement in a case study of malignant histiocytosis: a negative model of morphine as an immunoregulator.

In a patient diagnosed with histiocytic medullary reticulosis (HM), we examined immunocytes for their responsiveness towards known signaling molecules. Both the granulocytes and monocytes were found to exhibit a high level of spontaneous activation (96% compared to normal cells 7%; P < 0.001). These cells could not be downregulated when exposed to morphine. Following patient treatment with doxorubicin and cyclophosphamide, the immunocytes still exhibited a high spontaneous activation. They responded to morphine exposure in vitro with a cell rounding and becoming immobile for only 20 min whereas normal cells would remain round and immobile for up to 1-2 h. An examination of the plasma from the HM patient revealed that monocyte colony stimulating factor (MCSF) levels were elevated (6.4 and 5.78 compared to a control range of 1-1.75 ng/ml). In the HM patient, the immunocytes did not express the opiate selective and opioid peptide insensitive receptor, mu3, supporting the lack of opiate action. Given this finding, we incubated normal monocytes with MCSF and found that it significantly reduced the mu3 Bmax. Given the role of intracellular calcium in the activation process of immunocytes, we examined the action of various calcium channel blockers for their ability to inhibit the activated HM monocytes. The agents (nimodipine, cardiazem, and verapamil; 10[-9] M) were able to inhibit the HM-associated chemokinesis. Taken together, the data indicate that in the HM patient the immunocytes appear to be overactivated because stimulatory molecules are high and have the ability to downregulate the normal "braking" process. Additionally, the data indicate that MCSF deregulation may be involved as an initiating factor for this disorder.

Aged↗

PubMed1997

Cryopreserved veins in myocardial revascularization: possible mechanism for their increased failure.

BACKGROUND: Cryopreserved veins are used as conduits for myocardial revascularization. However, a high failure rate associated with their use has been reported anecdotally. METHODS: To find an explanation for the poor performance of cryopreserved vein grafts, we conducted a retrospective 5-year study on all patients at a single institution in whom cryopreserved vein grafts were used. We further performed in vitro studies measuring cell adhesion, nitric oxide production, and contractile capacity of saphenous vein, internal thoracic artery, and cryopreserved veins. RESULTS; Forty-one patients were identified in whom one or more cryopreserved veins were used as a last resort. Sixteen had events (death or recatheterization). Seven deaths occurred (17%). Event-free survival was 50% at 12 months. Activated granulocyte/monocyte endothelial adherence could be lowered in internal thoracic arteries and saphenous veins with morphine incubation (50% and 57%, respectively), but not in cryopreserved veins. Simultaneous increases in nitric oxide release were also found in internal thoracic arteries and saphenous veins, but not cryopreserved veins. In addition, cryopreserved veins showed a diminished contractile capacity under experimental conditions. CONCLUSIONS: In this highly select group of patients, cryopreserved veins had a high early failure rate, which may be partially due to the inability of the endothelium to participate in immunovascular processes.

Aged↗

PubMed1997

A rapid and sensitive quantitation method of endogenous morphine in human plasma.

Endogenous morphine is found at very low levels (pg/ml) in human plasma. Without technical modification, the usual techniques, i.e., RIA or HPLC, can not directly detect its presence. As a result the initial purification process is very crucial. In this report we demonstrate this opiate alkaloids determination in 2 ml of human plasma. Following an acidified precipitation of proteins in plasma, a solid-phase extraction, Sep-pak collection, was employed to concentrate the endogenous morphine. The extract was dissolved in a pH 8.9 phosphate buffer and then extracted into an organic solvent (chloroform and isopropyl alcohol). The initially purified sample was separated by HPLC and detected with an electrochemical detector of 500 mV and 0.02 Hz. The results showed that the recovery of morphine by this technique was 86+5.7%, and the sensitivity was 50 pg/ml. Compared to the detection sensitivity of the HPLC (2 ng/ml), this method increased the detection limit by 40-fold. With this method the concentration of endogenous morphine in plasma was determined as 80 pg/ml.

Acetonitriles↗

PubMed1997

Opiate signaling regulates microglia activities in the invertebrate nervous system.

1. Evidence supporting the presence in the invertebrate nervous system of a class of glial cells resembling vertebrate microglia was obtained in the freshwater snail Planorbarius corneus. These cells are easily identified by their immunopositivity to anti-pro-opiomelanocortin (POMC)-derived peptide antibodies. 2. Invertebrate microglia, as in vertebrates, exhibit macrophage-like activity in vivo and in cell cultures. These cells respond to the trauma of ganglionic excision and their organotypic culture by leaving their location around neurons and moving to the lesion site from which they migrate in the culture dish. 3. In vitro, these microglia undergo conformational changes and show phagocytic properties in the presence of bacteria or lipopolysaccharide. The activated cells also express tumor necrosis factor-alpha-like material and an increase in nitric oxide synthase, as shown by immunocytochemistry. 4. The inhibitory effect of morphine on the mobility and phagocytic activity of invertebrate microglia provide additional functional evidence for a possible role of opiate-like compounds in downregulating immunoregulatory processes, as also observed in the circulating immunocytes.

Animals↗

PubMed1997

Opposite effects of interleukin-2 and interleukin-4 on GABA-induced inward currents of dialysed Lymnaea neurons.

1. The effects of interleukin-2 (rhIL-2) and interleukin-4 (rhIL-4) were investigated on gamma-aminobutyric acid (GABA)-induced inward currents on isolated, identified neurons of Lymnaea stagnalis L. (Mollusca, Gastropoda) by using a concentration clamp technique. 2. It was shown that the interleukins modified the GABA-induced inward current in an opposite direction: rhIL-2 (2-100 U/ml) decreased the peak value of IGABA in a dose-dependent manner, whereas rhIL-4 (0.2-100 U/ml), on the contrary, potentiated it. Both types of modulation were partially or fully reversible. 3. The reversal potential of IGABA was not shifted by these cytokines. 4. The time-to-peak value and inactivation time constant of the gamma-aminobutyric acid (GABA)-induced current was decreased by rhIL-4. The modulatory effect of rhIL-4 was eliminated after conjugation of this cytokine with its antibody. 5. It appears that cytokines could play a role in regulating the neural excitability through GABA-erg mechanisms.

Animals↗

PubMed1997

Interleukin-10 stimulation of endogenous nitric oxide release from human saphenous veins diminishes immunocyte adherence.

Interleukin-10 (IL-10) is described as a cytokine that exerts immune downregulating actions. In this regard, our study indicates that IL-10 activity on human saphenous veins is coupled to nitric oxide (NO) release. We demonstrated this phenomenon by using in vitro real-time amperometric measurement of NO levels in explanted human saphenous veins after IL-10 exposure. IL-10-induced NO release can inhibit the adherence of monocytes (75.7 +/- 15 cells/600 microm2 of endothelial surface) and granulocytes (65 +/- 18 cells/600 microm2 of endothelial surface) from control values (250-300 cells/600 microm2 of endothelial surface; p < 0.005). This inhibition is directly sensitive to NO synthase inhibition. The specificity of the IL-10 effects is shown by its sensitivity to antibody. In vivo measurement of IL-10 levels during and after cardiopulmonary bypass surgery indicated that they are higher at 6 h after skin closure (1,400 pg/ml) compared with levels found during surgery (300 pg/ml). We surmise that the postsurgical increase of IL-10 levels may be an immunoregulatory attempt to downregulate the diffuse inflammation that has been shown to be associated with cardiopulmonary bypass surgery.

Aged↗

PubMed1996

Inhibition of the Met-enkephalin-induced K+ current in B-cluster neurons of Aplysia by nitric oxide donor.

The effects of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on a methionine-enkephalin (Met-E)-induced K+ current recorded from B-cluster neurons in Aplysia cerebral ganglion were investigated with voltage-clamp and pressure ejection techniques. Bath-applied SNP (10-25 microM) reduced the Met-E-induced K+ current in the neurons without affecting the resting membrane conductance and holding current. The inhibitory effects of SNP were reversible. Pretreatment with methylene blue (10 microM), a non-specific inhibitor of guanylate cyclase, and hemoglobin (50 microM), a NO scavenger, decreased the SNP-induced inhibition of the Met-E-induced current. Intracellular injection of 1 mM guanosine 3',5'-cyclic monophosphate (cGMP) or bath-applied 3-isobutyl-1-methylxanthine (IBMX; 50 microM), a nonspecific phosphodiesterase inhibitor, inhibited the Met-E-induced current. Furthermore, 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 microM), a more specific inhibitor of NO-stimulated guanylate cyclase, decreased the SNP-induced inhibition of the Met-E-induced current. These results suggest that SNP induces suppression of the Met-E-induced K+ current recorded from B-cluster neurons of Aplysia cerebral ganglion via stimulation of cGMP formation.

Animals↗

PubMed1996

Cannabinoid receptors are coupled to nitric oxide release in invertebrate immunocytes, microglia, and human monocytes.

The present study demonstrates that stereoselective binding sites for anandamide, a naturally occurring cannabinoid substance, can be found in invertebrate immunocytes and microglia. The anandamide-binding site is monophasic and of high affinity, exhibiting a Kd of 34.3 nM with a Bmax of 441 fmol/mg protein. These sites are highly selective, as demonstrated by the inability of other types of signaling molecules to displace [3H]anandamide. Furthermore, this binding site is coupled to nitric oxide release in the invertebrate tissues examined as well as in human monocytes. Interestingly, the cannabinoid-stimulated release of nitric oxide initiates cell rounding. Thus, these cannabinoid actions resemble those of opiate alkaloids. In this regard, we demonstrate that these signaling systems use the same effector system, i.e. nitric oxide release, but separate receptors. Last, the presence of a cannabinoid receptor in selected evolutionary diverse organisms indicates that this signaling system has been conserved for more than 500 million years.

Animals↗

PubMed1996

Morphine-induced conformational changes in human monocytes, granulocytes, and endothelial cells and in invertebrate immunocytes and microglia are mediated by nitric oxide.

We evaluated the contribution of nitric oxide (NO) to morphine-induced rounding of spontaneously activated (mobile) ameboid human monocytes, granulocytes, or arterial endothelial cells and invertebrate immunocytes and microglia. Morphine induced significant rounding and inactivation of ameboid cells within 20 min except for arterial endothelial cells, which became rounded 24 h after morphine exposure. The effects of morphine on cell conformation were blocked in the presence of N-nitro-L-arginine, a nitric oxide synthase inhibitor. Treatment of cells with the NO donor, sodium nitroprusside, induced cell rounding similar to that observed following morphine exposure, suggesting that NO release may mediate morphine-induced changes in cell conformation. The contribution of NO release to morphine-induced cell rounding was determined by direct evaluation of NO concentration in real-time using a NO-specific amperometric probe. Significant increases in NO concentration were observed 2 min after morphine stimulation, whereas morphine-induced NO release was markedly impaired by pretreatment with N-nitro-L-arginine or the opiate alkaloid antagonist, naloxone. In contrast, opioid peptides failed to induce NO release, consistent with our previous observations that demonstrated the failure of opioid peptides to promote cell rounding. Taken together, these data suggest that morphine-induced NO release may be mediated by activation of the opiate alkaloid-selective, opioid peptide-insensitive micro3 receptor, and that functional coupling of morphine to NO production has been conserved during evolution and may modulate cellular activation.

Animals↗

PubMed1996

Morphine stimulates nitric oxide release from invertebrate microglia.

Morphine stimulates nitric oxide (NO) release in human endothelial cells. To determine whether this mechanism also occurs in invertebrates, the mussel Mytilus edulis was studied. Exposure of excised ganglia to morphine for 24 h resulted in a significant dose-dependent decrease in microglial egress that was naloxone sensitive. In coincubating the excised ganglia with morphine and the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), an increase in microglial egress was observed, suggesting that morphine may stimulate microglia to release NO. Morphine exposure to these cells in vitro resulted in NO release (39.4 +/- 4.9 nM), a phenomenon found to be naloxone sensitive (10(-6) M; NO level = 5.9 +/- 2.6 nM) and L-NAME sensitive (10(-4) M; NO level = 2.8 +/- 1.8 nM). Opioid peptides did not stimulate NO release, indicating that the process was mediated by the opiate alkaloid selective mu 3 receptor. Coincubation of microglia with L-arginine or the superoxide scavenger, superoxide dismutase, resulted in significantly higher NO levels observed following morphine stimulation. Taken together, the data demonstrate that morphine can stimulate NO release in cells obtained from an invertebrate that represents an animal 500 million years divergent in evolution from man, underscoring the significance of this process and further substantiating the critical importance of morphine as a naturally occurring signal molecule.

Animals↗

PubMed1996

Surgical anticipatory stress manifests itself in immunocyte desensitization: evidence for autoimmunoregulatory involvement.

The immunocyte behavior (conformational changes and locomotion in response to signal molecule challenge) in patients about to undergo elective cardiac surgery was studied to elucidate the effect of psychological anticipatory stress on the immune system. Granulocytes and monocytes from 10 patients and 35 non-surgical controls were examined. Computer-assisted microscopic image analysis, capable of measuring cellular conformational and velocity changes, was used to measure the responsiveness of these immunocytes to peptidergic and cytokine stimulation. Immunocyte desensitization would appear to account for the reduction in their abilities to respond to chemotaxic challenge associated with the pre-cardiac surgery state. Their abilities to respond to D-Ala2-Met-enkephalinamide (DAMA) were observed only at much higher concentrations than previously reported (10-11 M vs. 10-9 M prior to surgery). This finding, together with the observed decrease in adrenocorticotropin levels compared to non-surgical controls, suggests that neutral endopeptidase activity was elevated just prior to surgery. Indeed, neutral endopeptidase activity is statistically elevated in the pre-cardiac surgery state. Furthermore, glucocorticoid levels remained constant, within normal resting limits, in both groups. Thus, surgical anticipatory stress may manifest itself, in part, as a desensitization of various immunocytes. Thus, a psychological anticipatory stress response may be a precipitant of the desensitization. Although this desensitization seemed not to involve the entire hypothalamic-pituitary-adrenal axis, the data suggest that psychological anticipatory stress may initially involve and influence autoimmunoregulation.

Adrenocorticotropic Hormone↗

PubMed1996

Hyperstimulation of leukocytes by plasma from cardiopulmonary bypass patients is diminished by alpha-MSH pretreatment.

Cardiopulmonary bypass (CPB) results in a diffuse inflammatory response characterized in part by hyperstimulation of leukocytes. We have previously shown that this hyperstimulation appears to be due, in part, to an increase in the release of biological response modifiers (BRMs) such as cytokines. In the present study, we evaluated the ability of a naturally occurring immunocyte inhibitory substance, alpha-melanocyte-stimulating hormone (alpha-MSH), to prevent the hyperstimulation caused by CPB. Monocytes and granulocytes were pretreated with alpha-MSH (10(-6) M) before exposing the cells to plasma obtained from patients who had undergone CPB, as CPB plasma would stimulate native monocytes and granulocytes in a manner similar to that observed in CPB patients. Pretreatment of these cells with alpha-MSH significantly diminished the hyperstimulation induced by CPB plasma in a concentration-dependent manner. In contrast, when the cells were first or simultaneously exposed to CPB plasma and then to alpha-MSH, alpha-MSH had no effect. Furthermore, use of the specific neutral endopeptidase inhibitor, phosphoramidon, significantly increased the efficacy of alpha-MSH in inhibiting CPB-induced immunocyte activation. The data demonstrate that pretreatment of monocyte/macrophages and granulocytes with alpha-MSH effectively inhibits the immune hyperstimulation induced by CPB-plasma exposure. In addition, the data strongly suggest that preexposure to other naturally occurring immune inhibitory substances may diminish the hyperstimulation associated with CPB. The study also further confirms that this hyperstimulation may, in part, be due to BRMs released from immunocytes.

Cardiopulmonary Bypass↗

PubMed1996

Aprotinin diminishes inflammatory processes.

Many of the recent reports concerning cytokine levels in cardiopulmonary bypass have documented changes in the levels of these trauma indicators. In the present report, we also document their levels but in the presence of Aprotinin. Aprotinin is a protease inhibitor used not only to diminish bleeding, but also to diminish elements of the diffuse inflammatory response associated with this type of surgery. We report in plasma obtained from 20 patients that initially interleukin-8 (IL-8) levels (53.4 +/- 7 pg/ml) plasma to 185.5 +/- 30 pg/ml) increased 20 min from the start of surgery. This is followed by IL-6 (5.3 +/- 1.1 to 200 +/- 50 pg/ml) peaking 15 h post surgery. These levels return to normal by day 3 postop. IL-1 beta and tumour necrosis factor (TNF) levels remained at baseline for the observation period. Associated with these changes in cytokine levels is the activity state of immunocytes (granulocytes and monocytes) noted by conformational changes obtained from computer-assisted microscopy. The cells exhibited an ameboid conformation and became mobile (67%), peaking at 120 min after surgery began and returned to a more rounded conformation with only 6% exhibiting the ameboid conformation by day three. In in-vitro experiments, where immunocytes not exposed to cardiopulmonary bypass were exposed to plasma obtained from patients having undergone this surgery, their activity level rose to 65%. In the same experiment, when Aprotinin was added to the cell-plasma mixture, the level of activation dramatically dropped to 25%. Thus, aprotinin was found at high doses to lower cytokine and cellular activation associated with the acute inflammatory responses of cardiopulmonary bypass, suggesting that this may be initiated by hyperstimulated immunocytes.

Acute-Phase Reaction↗