M Heckmann

DNA Double-Strand Breaks and Their Repair in Blood Lymphocytes of Patients Undergoing Angiographic Procedures

Objectives:To adapt &ggr;-H2AX immunofluorescence microscopy to assessment of induction and repair of DNA double-strand breaks (DSBs) in peripheral blood lymphocytes in patients undergoing angiographic procedures. Materials and Methods:The study was approved by the institutional ethics committee. After written informed patient consents were obtained, venous blood samples were taken from 19 patients (age 23–88 years) undergoing different angiographic procedures before, during, and after (10 minutes–24 hours) the examination. Individual DSB yields were visualized by detecting the phosphorylated variant of the histone H2AX (&ggr;-H2AX) in lymphocytes using fluorescence microscopy. Values were correlated with dose area product. Single in vitro irradiation with 50 mGy was performed in 14 and additional fractionated irradiation with 10 × 5 mGy over a time period corresponding to the angiography duration in 4 patients. The radiation doses to the blood delivered during angiography were estimated by comparing the number of DSBs after angiography with DSB yields obtained after in vitro irradiation. Results:In all patients in vivo and in vitro irradiation increased the number of DSBs (0.03–1.50 per cell), even if very small doses were applied (minimum 338 &mgr;Gy × m2). Thereafter in both in vitro and in vivo a rapid loss of &ggr;-H2AX foci was observed. The number of DSBs showed a linear correlation to dose area product for specific examination regions (eg, R = 0.85, pelvic and leg arteries). Calculated radiation doses to blood delivered during angiography ranged from 2.2 to 99.9 mGy and increased if fractioned in vitro samples were used as calibration instead of single in vitro irradiations at the same total dose. Conclusions:&ggr;-H2AX immunofluorescence microscopy is a reliable and sensitive method for measuring the induction and repair of DNA damage caused by ionizing radiation during angiography. To estimate radiation doses delivered during procedures and to consider patients individual repair capacity, postangiography DSB-yields should be compared with DSB-yields after fractioned in vitro irradiation imitating examination conditions.

Contrast Medium–enhanced Radiation Damage Caused by CT Examinations

PURPOSE To assess the effect of iodinated contrast medium (CM) on the induction and repair of DNA double-strand breaks (DSBs) in peripheral blood lymphocytes after computed tomographic (CT) examinations. MATERIALS AND METHODS This prospective study was approved by the institutional ethics committee; written informed patient consent was obtained from 37 patients. Venous blood samples were taken from patients before and at 30 minutes, 1 hour, 2.5 hours, and 5 hours after performing CT with (n = 18) or without (n = 19) intravenous administration of CM (iopromide or iomeprol). DSBs were assessed in lymphocytes by enumerating gammaH2AX foci. DSB levels after CT were compared with those obtained after in vitro irradiation. Cell culture experiments with peripheral lymphocytes and fibroblasts were performed with iopromide, iomeprol, or the control substance mannitol added before or immediately after x- or gamma-ray irradiation. DSBs were assessed at 5 minutes, 30 minutes, 2.5 hours, and 5 hours after irradiation. Data were analyzed by using linear regression and the one-tailed Welch and paired sample t tests. RESULTS The presence of CM during CT increases DSB levels in peripheral lymphocytes by approximately 30%. Cell culture experiments confirmed this effect and further showed that CM administered prior to x-ray irradiation increases the initial DSB yield but has no effect if added after irradiation or when gamma-rays are used instead of x-rays. CONCLUSION The highly sensitive gammaH2AX foci assay shows that CM-enhanced radiation damage incurred in peripheral lymphocytes during CT. However, it is unknown whether long-term bioeffects of low-dose ionizing radiation from CT examinations, such as cancer, are increased by using CM.

Ormond’s Disease or Secondary Retroperitoneal Fibrosis? An Overview of Retroperitoneal Fibrosis

Retroperitoneal fibrosis represents a rare inflammatory disease. About two thirds of all cases seem to be idiopathic (= Ormonds disease). The remaining one third is secondary and may be ascribed to infections, trauma, radiation therapy, malignant diseases, and the use of certain drugs. Up to 15 % of patients have additional fibrotic processes outside the retroperitoneum. The clinical symptoms of retroperitoneal fibrosis are non-specific. In sonography retroperitoneal fibrosis appears as a retroperitoneal hypoechoic mass which can involve the ureters and thus cause hydronephrosis. Intravenous urography and MR urography can demonstrate the typical triad of medial deviation and extrinsic compression of the ureters and hydronephrosis. CT and MRI are the modalities of choice for the diagnosis and follow-up of this disease. The lesion typically begins at the level of the fourth or fifth lumbar vertebra and appears as a plaque, encasing the aorta and the inferior vena cava and often enveloping and medially displacing the ureters. In unenhanced CT, retroperitoneal fibrosis appears as a mass that is isodense with muscle. When using MRI, the mass is hypointense in T 1-weighted images and of variable intensity in T 2-weighted images according to its stage: it may be hyperintense in early stages, while the tissue may have a low signal in late stages. After the administration of contrast media, enhancement is greatest in the early inflammatory phase and minimal in the late fibrotic phase. Dynamic gadolinium enhancement can be useful for assessing disease activity, monitoring response to treatment, and detecting relapse. To differentiate retroperitoneal masses, diffusion-weighted MRI may provide useful information.

Reversibility and Time-dependency of Contrast Medium Induced Inhibition of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (mtt) Conversion in Renal Proximal Tubular Cells In Vitro: Comparison of a Monomeric and a Dimeric Nonionic Iodinated Contrast Medium

Objectives:To evaluate the time-course and reversibility of toxicity of a low-osmolar and an iso-osmolar radiographic contrast medium on renal tubular cell cultures. Materials and Methods:LLC-PK1-cells were incubated with iomeprol, iodixanol, and mannitol (4.7–75 mg I/mL, 2–24 hours). Metabolic activity was assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide-(MTT) assay. Results:Iomeprol and iodixanol induced a time- and dose-dependent inhibition of MTT conversion (75%–19% and 70%–23% of control for iomeprol and iodixanol, respectively, at concentrations ranging from 4.7 to 75 mg I/mL after an incubation time of 2 hours and 64%–14% and 65%–12% of control after 24 hours). The mannitol induced inhibition of the MTT conversion was significantly weaker than that induced by iomeprol (99%–47% of control at concentrations corresponding to 4.7–75 mg I/mL after an incubation time of 24 hours, P < 0.001). After 24 hours incubation with iomeprol, iodixanol, or mannitol and a recovery time of 2 hours after removal of the test-solutions, there was only a small inhibition of MTT-conversion (89%, 88%, and 95% of control at 75 mg I/mL). Conclusions:Contrast medium induced cytotoxicity consisted of a reversible part and an irreversible part. There was no difference in cytotoxicity between iomeprol and iodixanol over a broad range of concentrations and incubation-times.

[X-ray-induced DNA double-strand breaks after angiographic examinations of different anatomic regions].

PURPOSE The aim of this study was to investigate DNA double-strand breaks (DSBs) in blood lymphocytes as markers of the biological radiation effects in angiography patients. MATERIALS AND METHODS The method is based on the phosphorylation of the histone variant H 2AX (gamma-H2AX) after formation of DSBs. Blood samples were collected before and up to 24 hours after exposure of 31 patients undergoing angiographies of different body regions. Blood lymphocytes were isolated, fixed, and stained with a specific gamma-H2AX antibody. Distinct foci representing DSBs were enumerated using fluorescence microscopy. Additional in-vitro experiments (10 - 100 mGy) were performed for evaluation of DBS repair. RESULTS 15 minutes after the end of fluoroscopy values between 0.01 and 1.50 DSBs per cell were obtained. The DNA damage level normalized to the dose area product was 0.099 (cardiac angiographies), 0.053 (abdominal angiographies), 0.023 (pelvic/leg angiographies) and 0.004 excess foci/cell/mGym (2) (cerebrovascular angiographies). A linear correlation was found between gamma-H2AX foci levels and the dose area product (abdomen: R (2) = 0.96; pelvis/legs: R 2 = 0.71). In-vivo on average 46 % of DSBs disappeared within 1 hour and 70 % within 2.5 hours. CONCLUSION gamma-H2AX immunofluorescence microscopy is a sensitive and reliable method for the determination of X-ray-induced DSBs during angiography. The DNA damage level depends on the dose, the exposed anatomic region, and the duration/fractionation of the X-ray exposure.