Search PubMed⌕ Search

Biomedical subjects

I L Bonta

Publications and source records attributed to I L Bonta.

At least 37 records · Page 2Linked to original sources
PubMed1992

Lethal and non-lethal course of endotoxic shock is determined by interactions between tumor necrosis factor, platelet activating factor and eicosanoids.

Continuous lipopolysaccharide (LPS) infusion in pigs induced death in approximately half of the animals and a prolonged state of shock (up to 3 hours of experimental observation period, i.e., two hours after discontinuation of LPS infusion) in the surviving animals. Lethal-induced shock was marked by huge release of Tumor Necrosis Factor (TNF) into the blood, whereas eicosanoid and Platelet Activating Factor (PAF) levels remained unchanged. In pigs surviving LPS-infusion but still remaining in a state of shock, transient increases in PAF and thromboxane levels were observed, whereas prostacyclin and leukotrienes values remained above normal levels up to the end of the observation period. It is concluded that different types of mediators play a role in LPS-induced lethal shock as compared to non-lethal prolonged state of shock.

Animals↗
PubMed1991

Sensitization enhances the adenylyl cyclase responsiveness in alveolar macrophages. Changes induced at post-receptor level.

Using membrane fractions (MF) from guinea pig alveolar macrophages (AM), we investigated the effects of sensitization and antigen challenge on the stepwise activation of adenylyl cyclase considering receptor binding, G-protein coupling and direct stimulation of the enzyme. Receptor binding studies, using [125I]ICYP as the beta-adrenoceptor specific ligand, show that neither receptor number (Bmax) nor receptor affinity constants (Kd values) were affected by sensitization or antigen challenge. Using forskolin as a direct stimulant of AC, alterations in the enzymatic activity of AC could be excluded. Pretreatment of the different MF with cholera toxin (CT, a toxin which eliminates GTPase activity) and subsequent stimulation of AC with GTP, shows an increased responsiveness in MF from sensitized and antigen challenged AM. In addition, pretreatment of MF from naive AM with increasing doses of CT results in a maximal AC response at the higher concentrations used (50-100 micrograms/mL), an effect not observed in MF from sensitized and antigen challenged AM. In these MF, the AC response still increases after pretreatment with such doses of CT. These data suggest that the enhanced AC responsiveness in AM, induced by sensitization and antigen challenge, results from alterations in alpha s-subunits.

Adenylyl Cyclases↗
PubMed1991

Inflammation amplifies the antitumor cytostasis by human peritoneal macrophages.

The effect of an inflammatory environment on the antitumor cytostatic ability of human macrophages was examined. Peritoneal macrophages of patients on continuous ambulatory peritoneal dialysis (CAPD) were collected, when CAPD was without complication, during an intercurrent infectious inflammation and after recovery. Inhibition of 3H-thymidine uptake served as a measure of cytostasis by macrophages co-cultured with target murine cells MOPC-315 plasmacytoma, WEHI-3B myelomonocytic leukemia and L929 transformed fibroblasts. Macrophages from inflammatory peritoneum expressed a markedly enhanced cytostasis, irrespective of the nature of the tumor cell. Endotoxin (LPS) challenge of inflammatory macrophages failed to further reinforce the cytostasis towards MOPC-315 plasmacytoma, but reinforced the cytostasis towards WEHI-3B leukemia (sensitive to inhibition by IL-1) and towards L929 (sensitive to TNF alpha). Cytostasis by supernatants of human peritoneal macrophages against L929 was markedly inhibited by anti-rHuTNF alpha and against WEHI-3B by anti-rHuIL-1 beta. The results suggest a link between inflammatory function and antitumor cytostasis by macrophages. This link is constituted by mediators involved in the activation process of macrophages.

Animals↗
PubMed1991

Serum levels of tumor necrosis factor determine the fatal or non-fatal course of endotoxic shock.

The role of tumor necrosis factor alpha (TNF alpha) in endotoxin-induced shock was investigated in pigs receiving 5 micrograms kg-1 of Escherichia coli endotoxin (LPS) during 60 min of continuous infusion into the superior mesenteric artery. LPS concentration in aortic plasma, as determined by a chromogenic Limulus amoebocyte lysate (LAL) test, reached a peak of approximately 1000 ng l-1 during LPS infusion, and declined rapidly after discontinuation of the infusion. Serum TNF levels were determined by a bioassay using the L929 murine transformed fibroblast line. Eight of the 17 animals infused with LPS died within 30 min after beginning LPS administration, while the other 9 pigs survived beyond the experimental observation period of 3 h, although they were in a state of shock. No difference in LPS concentration was found between the survivors and the non-survivors. However, the serum TNF levels in non-survivors were significantly higher than in survivors when measured at 30 min after beginning LPS administration. In survivors, the peak increase in serum TNF levels was measured at 60 min after the beginning of LPS injection and returned rapidly to the baseline values. Although the role of TNF inducing rapid death seems to be dominant, the hemodynamic, hematology and blood chemistry disturbances seen during shock continued in survivors long after the return of TNF to baseline levels. These findings indicate that besides TNF other mediators are also involved in the LPS infusion-induced shock.

Anaphylaxis↗
PubMed1991

Sequential release of eicosanoids during endotoxin-induced shock in anesthetized pigs.

The release of eicosanoids during endotoxin shock was investigated in anesthetized pigs receiving 5 micrograms/kg Escherichia coli lipopolysaccharide (LPS) over 60 min into the superior mesenteric artery. TXB2, 6-keto PGF1 alpha and LTB4 concentrations in blood obtained from the superior mesenteric vein (SMV), right ventricle (RV) and aorta, during LPS infusion and an additional period of 2 h, were assessed along with hemodynamic variables, blood gases and pH and laboratory parameters. Half of the animals died within 30 min after termination of LPS infusion (non-survivors, n = 8), while the other half survived the experimental period of 3 h, though in a shock state (survivors, n = 9). The non-surviving pigs demonstrated progressively reduced cardiac output, hypotension and hypoperfusion in all organs. The surviving pigs demonstrated also a reduced cardiac output, which however was compensated by an elevated systemic vascular resistance resulting in a maintenance of arterial blood pressure. After exhausting this compensation the flow to non-vital organs increased and consequently arterial blood pressure was reduced resulting in hypoperfusion. In survivors a marked, though, transient increase was measured in concentrations of TXB2 and 6-keto PGF1 alpha level. A significant increase was measured in plasma concentration of LTB4 in SMV without any elevation in RV and aorta. LTB4 production started when prostanoid release had decreased. In contrast to survivors, no changes could be observed in eicosanoid release for non-survivors. A correlation was observed between systemic vascular resistance and TXB2 to 6-keto PGF1 alpha ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Effects of hyperosmolarity on human isolated central airways.

1. We studied the effect of hyperosmolarity on human isolated airways because a better understanding of the effect of hyperosmolarity on the human airway wall may improve insight into the pathophysiology of hyperosmolarity-induced bronchoconstriction in asthma. 2. In cartilaginous bronchial rings dissected from fresh human lung tissue, hyperosmolar krebs-Henseleit buffer (450 mosM, extra sodium chloride added) evoked a biphasic response: a rapid relaxation phase (peak after 5.0 +/- 0.3 min) followed by a slow contraction phase (peak after 25.4 +/- 0.8 min). 3. With the histamine (H1) receptor antagonist mepyramine, the contraction phase was reduced to 41.2% of the control value (P less than 0.001), with atropine to 50.0% (P less than 0.01), with the local anaesthetic lignocaine to 48.7% (P less than 0.05) and with mepyramine together with atropine to 19.2% (P less than 0.001). 4. With the inhibitor of neutral metalloendopeptidase, phosphoramidon, the contraction phase increased to 128.0% of the control value (P less than 0.05) and after removal of the epithelium to 131.8% (P less than 0.05). 5. Indomethacin, the leukotriene C4/D4 (LTC4/D4) antagonist FPL 55712 or the blocker of nerve conduction, tetrodotoxin, had no effect on the contractile phase. 6. The relaxation phase was not altered by any of these drugs nor by epithelial denudation. The relaxation phase was also unchanged in the presence of alpha-chymotrypsin, which degrades muscle relaxing peptides such as vasoactive intestinal peptide. 7. Hyperosmolar buffer slightly increased the sensitivity and maximal response to methacholine as well as the cholinergic twitch to electric field stimulation. 8. We conclude that hyperosmolarity releases acetylcholine, histamine and neuropeptides in the human airway wall in sufficient quantities to contract airway smooth muscle. This release itself or its effect on airway muscle is modulated by the airway epithelium. The mechanism of the relaxation phase may be an unknown smooth muscle relaxing substance or a direct effect on the airway muscle, related to ion fluxes.

Acetylcholine↗
PubMed1991

Sequential release of tumour necrosis factor, platelet activating factor and eicosanoids during endotoxin shock in anaesthetized pigs: protective effects of indomethacin.

1. The effects of indomethacin were investigated on haemodynamics, haematological and blood glucose values, and the release of tumour necrosis factor (TNF), platelet activating factor (PAF) and eicosanoids in anaesthetized pigs receiving 5 micrograms kg-1 E. coli lipopolysaccharide (LPS) over 60 min into the superior mesenteric artery. The animals were observed for an additional period of 2 h after the termination of LPS infusion. 2. Eight of the 17 animals infused with LPS and not treated with indomethacin died within 30 min after the beginning of LPS infusion (non-survivors), while the other 9 survived the experimental period of 3 h though in a state of shock (survivors). 3. No alterations were observed in plasma concentrations of PAF and eicosanoids (thromboxane B2 (TXB2), 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) and leukotriene B4 (LTB4] in non-survivors. However, a marked increase was detected in TNF release. A significant, though transient, increase in concentrations of PAF, TNF and eicosanoids occurred in the survivors. The peak in the concentrations of PAF and TXB2 preceded the maximum in TNF values in survivors. 4. Another group of 7 LPS-infused pigs was treated with indomethacin (2 mg kg-1, i.v. bolus 60 min before the start of LPS infusion, followed by a continuous infusion of 3 mg kg-1 h-1). This treatment prevented death and shock despite the high concentrations of circulating TNF and PAF. Concentrations of cyclo-oxygenase enzyme products were reduced, whereas LTB4 release was not affected. The effect of indomethacin on haemodynamic changes occurred earlier than on cyclo-oxygenase products.5. In another group of 6 pigs indomethacin (2mg kg- 1, i.v.) was given 20-25 min after the start of LPS infusion at which time mean arterial blood pressure (MABP) had decreased below 40mmHg indicating imminent death. This indomethacin treatment immediately reversed the hypotension, restored the organ perfusion, delayed the haemoconcentration and thrombocytopenia and prevented death. However, TNF and PAF concentrations remained elevated. Concentrations of cyclo-oxygenase products studied were reduced by the end of the observation period, whereas LTB4 production was unaffected.6. The decrease in MABP induced by exogenous PAF was temporarily prevented by indomethacin.7. These data indicate that the beneficial effect of indomethacin in LPS-induced septic shock is related to cyclo-oxygenase inhibition as well as to a direct vasoconstrictor property of the drug.

Anesthesia↗
PubMed1991

Effect of cooling on responses of isolated human airways to pharmacologic and electrical stimulation.

We studied the effect of cooling on the responses of isolated human airways to the beta-agonist isoproterenol, the alpha/beta-agonist norepinephrine in the presence of the beta-blocker timolol, methacholine, leukotriene C4 (LTC4), and histamine. In addition, the effect of cooling on baseline airway tone and responses to electric field stimulation (EFS) was studied. At 27 degrees C the sensitivity (-logEC50) and maximal response to isoproterenol were unchanged. No measurable response was found to alpha-adrenergic stimulation with norepinephrine + timolol either before or during cooling. At 27 degrees C and 21 degrees C the sensitivity and maximal contraction to methacholine and LTC4 as well as the contraction to a single dose of histamine were reduced. Cooling diminished baseline airway tone. EFS produced a rapid cholinergic contraction followed by a deflection below baseline and a sustained noncholinergic contractile response, which was substantially reduced by the LTC4/D4 receptor antagonist FPL 55712 (11.5 microM) at all three temperatures. Cooling decreased the cholinergic response to EFS and increased the sensitivity to EFS-induced relaxation. In contrast, the sustained noncholinergic contractile response to EFS was not changed, suggesting that cooling facilitates the synthesis of LTC4/D4 that follows EFS and/or inhibits its inactivation. We conclude that in nonasthmatic, isolated human airways slow cooling of the airway wall down to 21 degrees C does not cause bronchoconstriction and does not increase the responsiveness to contractile or relaxing agonists. However, cooling increases the sensitivity to EFS-induced relaxation and might facilitate the accumulation of leukotriene C4/D4 in the airway wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Effects of zymosan-activated human granulocytes on isolated human airways.

In asthma a temporal association exists between the late allergic reaction (LAR), the influx of granulocytes into the airway wall, and an increase in bronchial responsiveness. We therefore tested the hypothesis that activated human granulocytes constrict isolated human airways and increase their sensitivity to cholinergic stimuli. Bronchial rings were dissected from 23 lung tissue specimens collected at thoracotomy and studied isotonically in organ baths. Airways were incubated with 1, 2, 5, 10, or 20 x 10(6) granulocytes from normal or atopic donors. Activation of the cells with serum-treated zymosan (STZ, 0.2 mg/ml), which itself did not alter baseline airway caliber, resulted in a bronchoconstriction proportional to the number of zymosan-activated granulocytes (ZAG) present (rs = 0.79, p less than 0.001). This contraction was reduced by about 70% with the leukotriene C4/D4 receptor antagonist FPL 55712 (11.5 microM; p less than 0.001) or with the lipoxygenase inhibitor nordihydroguaiaretic acid (10 microM; p less than 0.001). The scavengers of activated oxygen molecules superoxide dismutase (300 U/ml) and bovine catalase (5,000 U/ml), the cyclooxygenase inhibitor indomethacin (10 microM), or the histamine (H1) receptor antagonist mepyramine (2.8 microM) had no effect. Granulocyte suspensions from atopic donors contained more eosinophils (p less than 0.001), and the magnitude of the contraction to 10 x 10(6) ZAG was related to the proportion of eosinophils (rs = 0.66, p less than 0.01). The sensitivity of the airways to methacholine was unchanged in the presence of 1, 2, or 5 x 10(6) ZAG and decreased with 10 or 20 x 10(6) ZAG (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

GTP-related difference in cyclic AMP production between resident and inflammatory human peritoneal macrophages.

In macrophages cyclic AMP (c-AMP) plays an important role in regulating many activities such as phagocytosis, migration and tumoricidal activity. High intracellular levels of c-AMP are negatively correlated with these activities. In earlier studies we have shown that c-AMP levels in inflammatory human peritoneal macrophages (IM) were markedly lower when compared to levels in resident macrophages (RM). This is in line with the fact that c-AMP down-regulates macrophage activity. To our knowledge no data are available on the mechanism underlying the difference in c-AMP production between RM and IM. In this study the difference in c-AMP production between RM and IM has been investigated on the level of receptor and G-protein-related mechanisms. Macrophage membranes were incubated with different agents i.e. prostaglandin E2 (PGE2), prostacyclin I2 (PGI2), isoprenalin (ISO) and sodium fluoride (SF). Additionally, the capacity of IM and RM to hydrolyse quanosine triphosphate (GTP) was measured. Only in the presence of GTP (10(-4) M) could the c-AMP difference be detected (RM = 51 +/- 4.4 pmol/mg protein/min +/- S.E., n = 22, IM = 32.8 +/- 5.2 pmol/mg protein/min +/- S.E., n = 10, p less than 0.01). After receptor stimulation with PGE2, PGI2 and ISO, c-AMP levels increased to the same extent in both IM and RM with no effect on the GTP-related difference. After SF stimulation, c-AMP levels in RM and IM increased to the same level (RM = 63 +/- 8 pmol/mg protein/min, n = 14, IM = 58 +/- 11 pmol/mg protein/min, n = 13).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1991

Peritoneal macrophages from patients on continuous ambulatory peritoneal dialysis have an increased capability to release tumour necrosis factor during peritonitis.

We have reported previously that human peritoneal macrophages collected from patients on Continuous Ambulatory Peritoneal Dialysis (CAPD) during an episode of peritonitis secrete increased amounts of interleukin-1 (IL-1), as compared to those collected during an infection free period, provided the cells were stimulated in vitro by LPS. We now report that such macrophages release also higher amounts of Tumor Necrosis Factor (TNF), if collected during peritonitis and stimulated subsequently in vitro by LPS. The increase in release of TNF was ascertained by radio-immunoassays as well as by bioassay of cytostatic effect against the highly sensitive TNF target-cell line L929 murine transformed fibroblasts. The present reported results, in addition to previously reported data on release of IL-1, indicate that induction of release of cytokines from human peritoneal macrophages is a dual stepwise process: first priming in vivo in an inflammatory environment and, secondly stimulation in vitro by LPS.

Adult↗
PubMed1991

Cyclic nucleotides in human macrophages: effects of atrial natriuretic factor and nitroprusside on cGMP and cAMP production.

Atrial natriuretic factor (ANF, 10(-7) M) and sodium nitroprusside (SNP, 10(-5)-10(-3) M) stimulated cGMP production in human peritoneal macrophages (HPM). This suggests the existence of two separate forms of guanylate cyclase in HPM, e.g. the receptor-related form by ANF and the soluble form by SNP. In parallel with the rise in cGMP levels, both agents provoked a decrease in cAMP levels. Increasing the concentration of the phosphodiesterase inhibitor IBMX (0.2 mM to 1.0 mM) in the incubation media resulted in a significantly greater rise in cGMP levels which was accompanied by a profound decrease in cAMP levels. ANF did not exert any direct or GTP-related effect on cAMP production, which is in contrast to its action in other tissues. These results suggest that cAMP levels can be modulated through a cGMP signal, most likely at the production level. Results also give substantial evidence for the presence of a ANF receptor site on human peritoneal macrophages.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Platelet activating factor is one of the mediators involved in endotoxic shock in pigs.

The role of platelet activating factor (PAF) in endotoxic shock was investigated in anaesthetized pigs receiving 5 micrograms/kg E. coli endotoxin (LPS) into the superior mesenteric artery over a 60 min period. Concentrations of PAF and tumor necrosis factor (TNF) were measured in blood obtained from the superior mesenteric vein and aorta before, during and 60 min after the LPS infusion. The effect of 4 mg/kg of BN 52021, a PAF receptor antagonist, given as a bolus injection 5 min prior to LPS infusion and/or PAF administration into the superior mesenteric vein was studied on systemic and regional hemodynamic variables. Eight of the 17 animals infused with LPS died within 30 min after start of LPS, while the other 9 survived the experimental period of 3 h, though in a shock state. In survivors, PAF concentration in both superior mesenteric vein and aorta increased twenty-fold at 30 min of endotoxaemia, but rapidly returned back towards normal values. No changes in PAF release, but a marked rise in TNF production were measured in non-survivors. Exogenous administration of PAF (0.01 micrograms/kg) produced similar hemodynamic effects as observed in survivors. BN 52021 markedly reduced the effects of PAF on arterial blood pressure for over 1 h. Treatment with BN 52021 (4 mg/kg), injected 5 min prior to LPS infusion, failed to exert any effect on the surviving rate. However, in survivors all circulatory and laboratory parameters studied were improved after treatment with BN 52021. PAF release observed during LPS infusion in survivors may play a role in the development of shock; however, its role in the rapid death seems to be negligible. Present results clearly demonstrate that endotoxin shock is not crucially dependent on one class of mediators.

Animals↗