Effect of tumor necrosis factor-α and interferon-γ on the growth of human prostate cancer cell lines

Human recombinant tumor necrosis factor- (rTNF-, 10^-12–10^-8 M) inhibited the proliferation of androgen-dependent LNCaP cells by 32–56%. In contrast, proliferation of androgen-independent PC-3 and JCA-1 cells was only slightly inhibited, or not inhibited at all, respectively. Human recombinant interferon- (rIFN-, 500 U/ml) decreased proliferation of PC-3 and JCA-1 cells by 35% and 53%, respectively, but had no effect on LNCaP cells. Interestingly, the combination of rIFN- and TNF- had greater antiproliferative effects on JCA-1 cells than treatment with either cytokine alone. However, the antiproliferative effects of this combination were similar to those observed for PC-3 or LNCaP cells treated with rIFN- or TNF- alone, respectively. These data suggest that some forms of androgen-independent prostate cancer may benefit from a combination therapy of IFN- and TNF-, while the use of IFN- alone may be more efficacious in others.     

Changes in the productivity of cytokines and active-oxygen in peripheral blood cells following surgery

An investigation was carried out on the productivity of cytokines and active-oxygen by peripheral blood cells during the pre- and post-operative periods. While the preoperative production of tumor necrosis factor (TNF) and interleukin-l (IL-1) was elevated, that of lymphotoxin (LT) and interferon- (IFN-) were slightly suppressed. In the postoperative period the peak TNF and IL-1 and active-oxygen productivity was elevated, while LT and IFN- productivity was suppressed in patients with an intraoperative bleeding volume of more than 1,000 ml compared to those with that of less than 1,000 ml. Thus, stress stimulates the TNF and IL-1 and active-oxygen producing system, that is, the macrophage-neutrophil system, and suppresses the LT and IFN- system, being, the inflammatory helper T cell system, in the early postoperative period.     

Immunological comparison between prostate-specific antigen and γ-seminoprotein

Summary Prostate-specific antigen (PA) and -seminoprotein (-Sm) were compared by immunocytochemical, immunodiffusion and immunoblotting methods using rabbit anti-PA antibody and rabbit anti--Sm antibody. Enzyme immunoassys (EIAs) were developed for measurements of PA and -Sm to determine a correlation between serum PA and -Sm levels in patients with prostate cancer. The patterns of localization and distribution of PA and -Sm were identical in prostate tissue sections, including benign and cancerous human prostacs. The immunodiffusion study showed that the antigens with which anti-PA antibody and anti--Sm antibody reacted in seminal plasma and prostate tissue homogenates were identical to each other. In the immunoblotting study, anti-PA antibody and anti--Sm antibody recognized a single antigen corresponding to a molecular weight of approximately 33,000 both in seminal plasma and prostate tissue homogenates. The EIAs developed in this study were sensitive, specific, and reproducible, and the correlation between serum PA and -Sm values determined by these EIAs was highly significant (r=0.99, P(0.001). These results indicated that PA and -Sm were immunologically identical and that serum PA and -Sm determined by immunoassays using anti-PA antibody and anti--Sm antibody should be evaluated as identical tumor markers for serodiagnosis of prostate cancer.     

Expression of interferon-γ receptors on bladder cancer cells: does it correlate with biological response?

Summary Previously we have shown a differential biological response of three human bladder cancer cell lines (RT4, RT112 and MGH-U1) to gamma interferon (IFN-). The present study examines the relationship between the biological response and the expression of the interferon- receptor on the tumour cell surface. Using a competitive radioligand binding assay and Scatchard analysis, we measured the number and affinity of the IFN- receptors on each of the above cell lines. Individual cells from each line expressed large numbers (29,100–41,800) of high-affinity receptors (k _d =2.4–3.9×10¹⁰M). There was no statistically significant difference in either of these parameters between the three lines. We therfore conclude that the biological response of these bladder lines to IFN- does not relate to the number or affinity of its receptor on the plasma membrane of these tumour cells.     

Serum VEGF and b-FGF profiles after tension-free or conventional hernioplasty

Background Angiogenesis is strongly influenced by vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF), whose production is also regulated by interferon (IFN)- and interleukin (IL)-10. The aim of this study was to evaluate the modifications of serum VEGF, b-FGF, IFN- and IL-10 levels in patients with inguinal hernia undergoing hernioplasty with the Lichtenstein technique (LH) using polypropylene mesh or with Bassini open conventional inguinal hernia repair (BH).Materials and methods Randomly, 16 patients underwent BH, and 16 were treated with the LH technique using polypropylene mesh. Blood samples were collected 24 h prior to surgery and then 6, 24, 48 and 168 h postoperatively. The serum concentrations of VEGF, b-FGF, IFN- and IL-10 were evaluated.Results In BH patients, a peak of VEGF synthesis at 6 h with a normalization of this parameter 24 h after surgery has been observed. In the same subjects, b-FGF synthesis increased after surgery reaching significant levels 48 h later. On the contrary, in LH patients, a decrease in the serum VEGF and b-FGF concentrations was detected after surgery and their increase afterwards. IL-10 was increased in both groups 6 h after operation and declined to preoperative levels 24 h afterwards. IFN- enhanced in LH patients 6 h after surgery, whereas no modifications were detected in BH subjects.Conclusions This preliminary study shows that VEGF and b-FGF modifications, associated with alterations of cytokine secretion, are detectable in human undergoing hernioplasty, and suggests that they could somehow influence in the wound-healing process.     

Stimulation of intercellular adhesion molecule-1 (ICAM-1) antigen expression and shedding by interferon-γ and phorbol ester in human renal carcinoma cell cultures: relation to peripheral blood mononuclear cell adhesion

In the present study we investigated the effect of interferon- (IFN-) and phorbol-12-myristate 13 acetate (PMA) on intercellular adhesion molecule-1 (ICAM-1) antigen expression and shedding in human renal carcinoma cell cultures. We also examined the functional consequences of ICAM-1 antigen expression and soluble ICAM-1 molecules on the adhesion of peripheral blood mononuclear cells (PBMC). Incubation of the human renal carcinoma cell line CaKi-1 with IFN- or PMA enhanced ICAM-1 antigen expression. The calcium ionophore, 4-bromo-calcium ionophore A23187 (Bromo-A23187) significantly enhanced the IFN- and PMA effect. Soluble ICAM-1 (sICAM-1) was detected in the supernatants of stimulated but not unstimulated cultures, and correlated significantly with cellular expression. Using ⁵¹Cr-labelled peripheral blood mononuclear cells in a cell adhesion assay, we demonstrated increased adhesion in IFN--treated CaKi-1 cultures, which was augmented by Bromo-A23187. This adhesion was blocked by preincubation of CaKi-1 cells with monoclonal antibody against ICAM-1 or by preincubation of PBMC with either monoclonal antibody against leucocyte function associated antigen-1 (LFA-1), a major receptor for ICAM-1, supernatants from treated cultures or purified sICAM-1 molecules. Thus, shedding of ICAM-1 may play a role during the escape from immunosurveillance by renal carcinoma cells.     

Acoustic Neurinoma and Its Treatment Using the Leksell γ-Knife as a Primary or Secondary Treatment

Over 4 years (1992–1996) we have treated 122 patients with unilateral acoustic neurinoma using the Leksell -knife; 121 patients had a follow-up of 2–48 months (median 24 months). Tumor volume was 0.1–17.8 cm³ (median 2.9 cm³); dose to the tumor margin was 10–17.5 Gy (median 12 Gy) delivered on 40–80% isodose (median 50%). A decrease in the tumor volume was observed in 41.3% of patients, the tumor volume was unchanged in 54.6%, and an increase in the tumor despite radio-surgery was observed in 4.1%. Hearing loss was detected in 17.4% of patients, and 3% of patients gained useful hearing after radiosurgery. The overall risk of the method is 4.3% of hearing loss. Weakness of the facial nerve was observed in 1.9% of patients; normalization of the weakness, which was present before radiosurgery, was observed in 6.3% of patients. The overall risk of facial weakness is 1% for -knife radiosurgery. Impairment of trigeminal neuropathy was observed in 5% of patients and improvement in 31%. Impairment of vertigo was observed in 5.8% of patients and improvement in 46%. Leksell -knife radiosurgery was the primary treatment in 97 patients (80.7%); microsurgical resection preceded radiosurgery in 24 patients (19.8%). Hearing loss and neuropathy of facial and trigeminal nerves before -knife radiosurgery were significantly more frequent in the group of patients with previous microsurgical resection than in the group with -knife radiosurgery as the primary treatment. After radiosurgery there was no significant difference in impairment or improvement of hearing, facial and trigeminal nerve neuropathy, and vertigo and imbalance for the groups of patients with previous microsurgery or primary -knife treatment. After -knife radio-surgery neuropathy of facial and trigeminal nerves in the group of patients with previous microsurgery was significantly worse.     

Cyclooxygenase-2 Inhibition Improves Macrophage Function in Melanoma and Increases the Antineoplastic Activity of Interferon γ

Background: Melanoma inhibits macrophage tumoricidal activity and increases the expression of cyclooxygenase-2 (COX-2). In this study, we sought to determine whether inhibition of COX-2 could restore macrophage function and hence maximize the antitumor activity of the immune stimulant interferon (IFN).Methods: Peritoneal macrophages were exposed to B16 melanoma-conditioned medium for 24 hours with or without the COX-2 inhibitor NS-398 and then were stimulated with lipopolysaccharide and IFN. Cytotoxic activity, nitrite production, and cytokine production by the stimulated macrophages were measured. In addition, B16 melanoma cells were implanted intradermally into mice treated with IFN (14,000 U on alternate days) alone or with a combination of IFN and a COX-2 inhibitor (NS-398 or nimesulide). Mice were assessed for tumor growth and survival.Results: Macrophage cytotoxicity and nitrite production were significantly suppressed by melanoma-conditioned medium (P < .01). This was prevented by 200 M of NS-398 (P < .05). In vivo, combined treatment with IFN and a COX-2 inhibitor caused a significant inhibition of tumor growth (P < .01) and improved survival (P = .02) compared with controls.Conclusions: COX-2 inhibition reversed melanoma-induced suppression of macrophage function, and combined treatment of IFN plus a COX-2 inhibitor was maximally effective in reducing tumor growth and improving survival.     

Photodynamic therapy and γ-irradiation of tumours: Effect of tumour-cell reoxygenation

The presence of adequate oxygen appears to be essential for photodynamic therapy (PDT) of tumours (1, 2). We used the mouse sarcoma 180 tumour model to investigate how the reoxygenation of the tumour cell population after a single exposure to -irradiation influenced the effect of photodynamic therapy. The combination of -irradiation with PDT leads to a significant enhancement of the therapeutic effect. The best effect is observed when the -irradiation precedes the PDT by 24 h, at which time reoxygenation of the tumour is greatest. Also, there is some enhancement of the effect when PDT is given before -irradiation, although the mechanism of this is not yet clear.     

Intratumoral IL-12 and TNF-α–Loaded Microspheres Lead To Regression of Breast Cancer and Systemic Antitumor Immunity

Background: Local, sustained delivery of cytokines at a tumor can enhance induction of antitumor immunity and may be a feasible neoadjuvant immunotherapy for breast cancer. We evaluated the ability of intratumoral poly-lactic-acid-encapsulated microspheres (PLAM) containing interleukin 12 (IL-12), tumor necrosis factor (TNF-), and granulocyte-macrophage colony stimulating factor (GM-CSF) in a murine model of breast cancer to generate a specific antitumor response.Methods: BALB/c mice with established MT-901 tumors underwent resection or treatment with a single intratumoral injection of PLAM containing IL-12, TNF-, or GM-CSF, alone or in combination. Two weeks later, lymph nodes and spleens were harvested, activated with anti-CD3 monoclonal antibodies (mAb) and rhIL-2, and assessed for antitumor reactivity by an interferon (IFN) release assay. Tumor-infiltrating lymphocyte (TIL) analysis was performed on days 2 and 5 after treatment by mechanically processing the tumors to create a single cell suspension, followed by three-color fluorescence-activated cell sorter (FACS) analysis.Results: Intratumoral injection of cytokine-loaded PLAM significantly suppressed tumor growth, with the combination of IL-12 and TNF- leading to increased infiltration by polymorphonuclear cells and CD8⁺ T-cells in comparison with controls. The induction of tumor-specific reactive T-cells in the nodes and spleens, as measured by IFN- production, was highest with IL-12 and TNF-. This treatment resulted in resistance to tumor rechallenge.Conclusions: A single intratumoral injection of IL-12 and TNF-–loaded PLAM into a breast tumor leads to infiltration by polymorphonuclear cells and CD8⁺ T-cells with subsequent tumor regression. In addition, this local therapy induces specific antitumor T-cells in the lymph nodes and spleens, resulting in memory immune response.     

IgG and complement receptor expression in children treated by peritoneal dialysis

Children treated by peritoneal dialysis (PD) are at increased risk of infections. IgG receptors (FcRs) and complement receptors (CRs) on white blood cells (WBCs) are important for the phagocytic process. We have investigated FcR and CR expression on monocytes, macrophages and neutrophils in blood and in peritoneal dialysis effluent (PDE) of 39 PD children. WBCs were isolated from blood and PDE, labelled with FITC-conjugated CD16 (FcRIII), CD32 (FcRII), CD64 (FcRI), CD11b (CR3) and CD35 (CR1) monoclonal antibodies, and analysed by flow cytometry. Peritoneal cells had lower percentages of FcR-positive or CR-positive cells than blood. On the other hand, the receptor number per cell [mean fluorescence intensity (MFI)] was higher on peritoneal macrophages and neutrophils than blood, except for CD16. The FcR and CR expression in blood and dialysate did not change significantly during the first year of PD treatment. During a peritonitis episode the MFI of all receptors in blood increased only on monocytes, with the exception of CD32. The percentages of FcR-positive and CR-positive macrophages and neutrophils in the PDE increased, whereas the MFI did not increase consistently. Peritoneal cells of PD children showed a lower percentage of FcR-positive and CR-positive neutrophils and macrophages, combined with an increased MFI, indicating a state of activation. Blood and peritoneal cells are capable of up-regulating the receptor expression during peritonitis but probably not to a maximum level.     

Expression of cytokines and growth factors in human glomerulonephritides

Numerous experimental studies point to the potential role of cytokines and growth factors in the pathogenesis of renal disease. However, from the various autocrine and paracrine mediators identified in vitro and in animal models, so far only a few have been demonstrated in selected human glomerulopathies. We examined two types of glomerulonephritis (GN): extracapillary GN with anti-neutrophil cytoplasmic autoantibodies (ANCA), an example of an acute form of GN, and mesangial IgA GN, usually a chronic form of GN, with immunocytochemistry, in situ hybridization and the polymerase chain reaction. Normal renal tissue from tumour nephrectomies served as a control. In ANCA-positive GN with active renal lesions (crescents, glomerular and vascular necrosis), infiltrating mononuclear cells in glomeruli and in the interstitium expressed interleukin (IL)-1, tumour necrosis factor (TNF)-, IL-2, interferon (IFN)-, platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-. Cytokine expression was also observed in activated resident cells, including endothelial cells, capsular epithelial cells, smooth muscle cells of vessel walls, fibroblasts and some tubular epithelial cells. In addition, we noted an increase in the cytokine and growth factor receptors TNF-R, IL-1R type II, IL-2R, IFN-R and PDGF-R. In contrast, in mesangial IgA-GN, IL-1, TNF-, IFN- and IL-2 were usually absent in glomeruli. Mesangial expansion in this disorder was accompanied by an increased expression of PDGF, PDGF-R, TGF- and IL-6 in mesangial areas. In both conditions a good correlation was observed between cytokine expression at the mRNA (in situ hybridization) and protein level (immunocytochemistry). These results demonstrate that different cytokine and growth factor patterns are expressed in the various forms of GN, and suggest that the local production of these peptides plays an important role in the pathogenesis and progression of human glomerulonephritides.     

Role of endogenous interferon gamma in murine tumor growth and tumor necrosis factor alpha antitumor efficacy

Background: The anticancer role of tumor necrosis factor-alpha (TNF-) has been limited by toxicity. These experiments evaluate blocking endogenous interferon-gamma (IFN-) activity to abrogate TNF- toxicity. Methods: C57Bl/6 mice bearing MCA 105 tumor were treated with TNF- and anti-IFN- antibody (Ab) to evaluate the effect on the acute lethality of TNF- and their efficacy as evaluated by tumor growth rate, tumor histology, and survival. Results: Anti-IFN- Ab decreased TNF- lethality. Anti-IFN- Ab alone increased tumor growth significantly more than did nonimmune IgG (p₂<0.0001). Tumor-bearing mice that received nonimmune IgG and TNF- had slower tumor growth (p₂<0.02) and a trend toward improved survival (p=0.07) compared with saline-treated controls. Anti-IFN- Ab abrogated the antitumor effect of TNF-, prevented acute tumor necrosis histologically, and resulted in tumor growth rate and host survival similar to that of controls. The findings in mice that received anti-IFN- Ab and high-dose TNF- were comparable with those in mice that received a lower, equitoxic dose of TNF- alone. Conclusions: Blocking endogenous IFN- accelerates tumor growth in this model and partially abrogates the toxic and antitumor activity of exogenous TNF- equally. This suggests that blocking endogenous IFN- activity is not a useful strategy for limiting TNF- treatment toxicity.Presented in part at the 45th Annual Cancer Symposium of The Society of Surgical Oncology, New York, New York, March 15–18, 1992.     

Case Report: Intracerebral Hemorrhage After γ-Knife Surgery for Metastatic Brain Tumor

The authors report a case of a 69-year-old man with metastatic brain tumors who died of spontaneous intracerebral hemorrhage 3 days after -knife surgery. He had been suffering from lung cancer with multiple systemic metastasis. Preoperative magnetic resonance images showed two well-defined round lesions with intratumoral hemorrhage in the left frontal and right occipital lobe. There was no bleeding tendency in the hematological examination and the patient was normotensive. -Knife surgery was performed on both lesions in a single session. However, the patient died of massive intracerebral hemorrhage from the left frontal lesion 3 days after the surgery. There have been no previous reports of mortality resulting from spontaneous intracerebral hemorrhage after -knife surgery in metastatic brain tumors documented in the literature. It is likely that the two events, -knife surgery and spontaneous intracerebral hemorrhage, occurred separately and were not associated. However, it is worth noting that there is a possibility of bleeding after -knife surgery, especially in a metastatic brain tumor with preexisting intratumoral hemorrhage as in our case.     

Mechanism of action of β-glycerophosphate on bone cell mineralization

Summary Experiments were performed to determine whether -glycerophosphate (-GP) promoted mineralization in vitro by modulating bone cell metabolic activity and/or serving as a local source of inorganic phosphate ions (Pi). Using MC3T3-E1, ROS 17/2.8, and chick osteoblast-like cells in the presence of -GP or Pi, we examined mineral formation, lactate generation, alkaline phosphatase (AP) activity, and protein and phospholipid synthesis. Neither -GP nor Pi modulated any of the major biosynthetic activities of the bone cells. Thus, we found no change in the levels of phospholipids, and the total protein concentration remained constant. Measurement of lactate synthesis showed that -GP did not effect the rate of anaerobic glycolysis. Evaluation of medium Pi levels clearly indicated that -GP was hydrolyzed by bone cells; within 24 hours, almost 80% of 10 mM -GP was hydrolyzed. It is likely that this local increase in medium Pi concentration promoted rapid mineral deposition. Chemical, energy dispersive X-ray, and Fourier transform infrared analysis of the mineral formed in the presence of -GP showed that it was nonapatitic; moreover, mineral particles were also seen in the culture medium itself. Experiments performed with a cell-free system indicated that mineral particles formed spontaneously in the presence of AP and -GP and were deposited into a collagen matrix. We conclude that medium supplementation with -GP or Pi should not exceed 2 mM. If this value is exceeded, then there will be nonphysiological mineral deposition in the bone cell culture.     

Localization and System Integration Tests as Quality Assurance for the Leksell γ-Unit

Quality control in stereotactic radiotherapy of brain lesions with the Leksell -unit or the LINAC-facility is a must, as missing the target is the most serious error that can occur in that kind of treatment. We developed a quality assurance program to reduce this risk. To evaluate the accuracy of the procedure, which defines the target, including all possible errors of the therapy chain, irradiations of phantoms were performed, using the so-called known and unknown target method. Accuracy is defined by the deviation of the irradiated target from the calculated target with digital images used for therapy planning. GafChromic MD-55 films, which have been irradiated by means of a special author-developed phantom, were applied for measuring the precision of the radiation unit. The results obtained for isocentric accuracy of the Leksell -unit were in good agreement with the measurements of the manufacturing company. The deviation measured with the 4-mm collimator helmet was up to 0.3 mm, including the CT images and the stereotactic frame less than 0.85 mm, respectively. The phantom designed for this purpose is useful in quality assurance measurements of this stereotactic therapy chain.     

Behςet’s disease,associated with subarachnoidal heamorrhage due to intracranial aneurysm

Summary Behets disease is an unusual medical condition in central Europe and North America, however more common in Turkey and Japan. It was originally described in Turkey, characterized by recurrent oral ulcers, genital ulcers and also uveitis. A variety of vascular lesions such as venous occlusions, arterial aneurysms and varices account for the high rate of morbidity and mortality with this disease. Arterial aneurysms most commonly occur in the abdominal aorta, femoral arteries and in the pulmonary arteries.To our knowledge there have been seventeen documented reports of patients with Behets disease combined with aneurysms of cerebral arteries. We describe a patient with Behets disease and subarachnoid haemorrhage due to a ruptured cerebral aneurysm.     

Up-regulation of interleukin-2 mRNA in children with idiopathic nephrotic syndrome

The current hypothesis for the pathogenesis of childhood idiopathic nephrotic syndrome (INS) favors the involvement of a T cell-mediated immune response. Various cytokines derived from T cells may play a critical role in INS. Previous studies have measured serum or urine cytokine levels and suggest an imbalance of the T cell-mediated immune response. To elucidate the true profile of T cell-derived cytokines, we determined interleukin (IL)-2, interferon (IFN)-, IL-4, IL-10, and tumor necrosis factor (TNF)- mRNA expression in children with INS. We collected mRNA from peripheral blood mononuclear cells together with plasma and urine from nine children in the acute and remission phases of INS. Expression of IL-2, IFN-, IL-4, IL-10, and TNF- mRNA was determined by a quantitative real-time PCR assay. Plasma and urine cytokine concentrations were measured using a specific enzyme-linked immunosorbent assay. These data were compared between the acute and remission phase in the same patients. The IL-2 mRNA levels were significantly higher in the acute phase than in the remission phase, whilst no significant difference was found in the other cytokines investigated. There was no significant difference in the plasma and urine cytokine concentrations between the acute and remission phase. Our results indicate increased expression of IL-2 mRNA in the acute phase of INS, suggesting that IL-2, at least in part, might be involved in the pathophysiology of childhood INS.     

Impaired interferon-α production in whole-blood cultures from bladder cancer patients

Summary Interferon- (IFN-) production was investigated in whole-blood cultures of 66 bladder cancer patients and 65 control subjects. IFN synthesis was induced with Sendai virus, and IFN activity was assayed in FL cells challenged with vesicular stomatitis virus (VSV). The mean levels of the IFN- produced were 5,724±2,288 IU/ml in the control subjects and 4,800±2,353 IU/ml in the bladder cancer patients. IFN- production was significantly suppressed in the bladder cancer patients compared with that in the control subjects (P (0.05). The impairment in IFN- production correlated with the tumor grade, and it was shown that the tendency toward decreased IFN- production was closely associated with the advancement of the tumor stage. Our results suggested that the decreased IFN- production may contribute to the disordered immunoregulation in bladder cancer patients.     

Antioxidant effect of γ-tocopherol supplied by propofol preparations (Diprivan) during ischemia–reperfusion in experimental lung transplantation

Free radicals are involved in ischemia-reperfusion injury and inflammatory processes. The commercial formulation of the anesthetic propofol contains -tocopherol and -tocopherol, which may exert antioxidant effects during transplantation. Animals were randomly assigned to a control group or experimental groups for lung transplantation after 3 and 24 h of ischemia. Individual tocopherols, malondialdehyde, biochemical indices, and hemodynamic, blood gas, and ventilatory parameters were determined during reperfusion. Results showed that administration of commercially available propofol provoked a time- and dose-dependent increment in serum -tocopherol and -tocopherol in control animals and in the group receiving lungs subjected to 3 h of ischemia, but not in the group with 24 h of ischemia. Malondialdehyde levels increased during reperfusion and did not differ significantly between the two experimental groups, which did not differ with respect to lung function either. -Tocopherol, supplied by the anesthetic, may act as an antioxidant that is consumed during reperfusion. This potential effect could be relevant to the choice of anesthetic agents in situations where free radical damage to tissues is expected.