A new cytogenetic approach for the evaluation of mutagenic potential of chemicals that induce cell cycle arrest in the G2 phase.

The aim of the present study was to develop and standardize a cytogenetic approach for evaluation of the mutagenic potential of chemicals that induce cell cycle arrest in the G2 phase. Even though cytogenetic end-points such as sister chromatid exchange (SCE) have been extensively used to indirectly assess the DNA-damaging potential of various chemicals, they are based on metaphase chromosome analysis. Cells delayed in G2 phase after chemical exposure are not included in conventional SCE analysis. The yield of SCEs obtained, therefore, can be biased, since predominantly undamaged cells proceed to metaphase without delay. To overcome this shortcoming of conventional SCE analysis, the use of a new cytogenetic approach for genotoxic studies is presented that enables the analysis of SCEs directly in G2 phase using drug-induced premature chromosome condensation in cultured peripheral blood lymphocytes. By means of this method, firstly, the possibility that SCE analysis in metaphase chromosomes underestimates the mutagenic potential of various chemicals was tested. Secondly, whether the genotoxic potential of suspected carcinogens could be evaluated using SCE analysis in G2 phase, even at exposures that arrest cells in G2 phase, was examined. Thirdly, whether an important part of the background variation in SCE frequency among individuals is due to the delay of affected cells in G2 phase, rather than to a true biological variation in the cytogenetic end-point used, was tested. The results showed that a higher SCE frequency was scored in G2 phase than in metaphase. Subsequently, the mutagenic potential of chemicals that temporarily arrest cells in G2 phase could now be evaluated more accurately. In addition, it may be of interest to further examine the involvement of cell cycle kinetics in the baseline SCE variation among individuals since a lesser SCE variability was observed when the analysis was carried out in G2 phase rather than at metaphase.

Influence of recombinant human erythropoietin therapy on plasma endothelin-1 levels during hemodialysis.

The correction of anemia with human recombinant erythropoietin (rHuEPO) in end stage renal disease is associated with hypertension in about one third of hemodialysis patients. The pathogenesis of the rHuEPO-induced hypertension is still uncertain, though evidence of the involvement of endothelial cells has emerged. The aim of this study was to determine plasma endothelin-1 during hemodialysis and to compare the endothelin-1 levels in hemodialysis patients with and without rHuEPO substitution. Nineteen stable patients (13 male and 6 female, mean age 62 +/- 11 years) with end stage renal disease were studied. Cuprophan dialysers (GFS 12, Gambro, Lund, Sweden) were used for hemodialysis in all cases. rHuEPO (40 U/kg s.c.) was administered to 10 patients. Blood pressure (BP; RR mmHg) and blood volume changes (deltaBV; hemoglobinometry %) were serially measured. Samples were taken before and every hour during hemodialysis. Plasma endothelin-1 was measured by ELISA (R&D Systems, Minneapolis, USA) and corrected for hemoconcentration. Endothelin-1 concentration was elevated before commencement of hemodialysis (1.16 +/- 0.36 pg/ml) when compared to healthy controls (ref. 0.3-0.9) and increased to 1.47 +/- 0.51 pg/ml by the end of the session (p<0.05). In patients under rHuEPO-substitution plasma endothelin-1 was higher when compared to patients without substitution before (1.25 +/- 0.3 vs. 1.05 +/- 0.3 pg/ml) and at the end of HD (1.62 +/- 0.5 vs. 1.28 +/- 0.3 pg/ml, p<0.05). There was no difference in BP and deltaBV between the two groups during treatment. Plasma endothelin-1 was higher in hemodialysis patients and there was a continuous rise in plasma endothelin-1 during a session. Comparison of two groups of hemodialysis patients with and without s.c. rHuEPO-replacement treatment revealed a significantly higher plasma endothelin-1 concentration in patients with s.c. rHuEPO treatment. However, the elevated endothelin-1 levels were not accompanied by arterial hypertension.

Urinary thymidine glycol as a biomarker for oxidative stress after kidney transplantation.

Reactive oxygen species are generated during ischemia-reperfusion tissue injury. Oxidation of thymidine by hydroxyl radicals (HO*) causes formation of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol). Thymidine glycol excreted in urine can be used as a biomarker of oxidative DNA damage. The aim of this study was to investigate the oxidative DNA damage in patients showing immediate allograft function after kidney transplantation, and to find out whether this damage correlates with glomerular and tubular lesions. Time dependent changes in urinary excretion rates of thymidine glycol, but also of total protein, albumin, low molecular weight (alpha1-microglobulin, beta2-microglobulin) and high molecular weight proteins (transferrin, IgG, alpha2-macroglobulin) were analyzed quantitatively and by polyacrylamide-gel electrophoresis in six patients. Urinary thymidine glycol was determined by a fluorimetric assay in combination with affinity chromatography and HPLC. After kidney transplantation the urinary excretion rate of thymidine glycol increased gradually reaching a maximum within the first 48 hours (16.56+/-11.3 nmol/m mol creatinine, ref. 4.3+/-0.97). Severe proteinuria with an excretion rate of up to 7.2 g/mmol creatinine was observed and declined within the first 24 hours of allograft function (0.35+/-0.26 g/mmol creatinine). The gel-electrophoretic pattern showed a nonselective glomerular and tubular proteinuria. The initial nonselective glomerular proteinuria disappeared within 48 hours, changing to a mild selective glomerular proteinuria. In this period (12-48 hours) higher levels of thymidine glycol excretion were observed, when compared to the initial posttransplant phase (13.66+/-9.76 vs. 4.31+/-3.61 nmol/mmol creatinine; p<0.05). An increased excretion of thymidine glycol is seen after kidney transplantation and is explained by the ischemia-reperfusion induced oxidative DNA damage in the kidney. In the second phase higher levels of excretion were observed parallel to the change from a nonselective to a selective glomerular and tubular proteinuria. An explanation may be sought in the repair process of DNA in the glomerular and tubular epithelial cells, appearing simultaneously with functional recovery.

Selenium deficiency and thyroid function in acute renal failure.

The lethality of acute renal failure exceeds 50% due to multiorgan dysfunction. In such critically ill patients a reduction of thyroid hormone concentrations without clinical symptoms or laboratory evidence of hypothyroidism frequently occurs. Selenium has recently been shown to play a major role in thyroid hormone metabolism. The aim of this study was to investigate the possible influence of selenium on thyroid hormone metabolism in acute renal failure. Changes in thyroid metabolism were related to the severity of multiorgan failure and to the clinical course. Thyroxine (T4), tri-iodothyronine (T3), free-T4, free-T3, thyrotropin (TSH), serum creatinine, and plasma selenium concentrations in 28 patients (mean age 60 +/- 13) with acute renal failure and multiple-organ dysfunction syndrome were determined initially, and every 3 days after hospital admission. The plasma selenium concentration was found to be reduced compared to normal controls (32 +/- 14 vs. 70-120 micrograms/L). T4 (56 +/- 15 nmol/L, normal range 64-148), T3 (1.31 +/- 0.38 nmol/L, normal range 1.42-2.46), free-T3 (3.1 +/- 1.0 pmol/L, normal range 4.7-9.0), and free-T4 (10.8 +/- 4.0 pmol/L, normal range 10.3-25.8) values were low in 50-70% of the patients at the time of presentation. Plasma TSH concentrations were within the normal range (0.59 +/- 0.79 mU/L, normal range 0.25-3.1), and no clinical symptoms of hypothyroidism were observed. T4 concentration was higher in patients who survived acute renal failure compared to nonsurvivors (62 +/- 22 vs. 51 +/- 16 nmol/L, p < 0.05). Plasma selenium concentration was lower in patients with a severe organ dysfunction syndrome (36 +/- 10 vs. 29 +/- 19 micrograms/L) and correlated with the number of organ failures in these patients (r = -0.247, p < 0.05). T4 and free-T4 values paralleled decreasing selenium concentrations (r = 0.35, p < 0.05). Thyroid hormone levels were reduced in patients with acute renal failure without an increase in TSH. An increase in T4 concentrations became apparent during treatment and may be related to a favorable outcome in acute renal failure. Thyroid hormone concentrations paralleled plasma selenium levels, indicating a possible influence of selenium on thyroid function in acute renal failure.

[An absent correlation between antioxidant blood concentrations and the remission response of preoperatively treated breast carcinomas]. / Fehlende Korrelation zwischen Antioxidanzienkonzentrationen im Blut und Remissionsverhalten präoperativ behandelter Mammakarzinome.

PURPOSE: Deleterious effects of ionizing radiation and some chemotherapeutic agents are predominantly caused by reactive oxygen agents which are detoxified by antioxidants. This study was designed to evaluate the modifying effects of vitamin A-, vitamin E- and selenium serum concentrations and glutathione peroxidase activity on preoperative radio- and chemotherapy of breast cancer. PATIENTS AND METHODS: Tumor volume, vitamin A-, vitamin E-, selenium serum concentrations and glutathione peroxidase activity in circulating erythrocytes were determined in 40 patients with breast cancer before treatment. Interstitial radiohyperthermia was given initially using a single dose of 10 Gy (HDR) combined with hyperthermia between 43.5 to 44.5 degrees C over 60 minutes followed by external beam radiotherapy with 50 Gy in 5 weeks. All patients received anthracyline or anthrachinone containing chemotherapy. Tumor response was determined by histopathological examination. Patients with complete and incomplete remissions were compared using the Wilcoxon test. Pre- and posttreatment tumor-volume differences were correlated with antioxidant concentrations (Spearman correlation coefficient). RESULTS: Twenty patients (50%) achieved a complete histopathologic tumor regression. This high complete remission rate was not related to the antioxidants under investigation (vitamin A: p = 0.32, vitamin E: p = 0.44, selenium: p = 0.68, glutathione peroxidase: p = 0.3). There was no correlation to pre- and posttreatment tumor-volume-differences either (vitamin A: p = 0.89, vitamin E: p = 0.67, selenium: p = 0.41, glutathione peroxidase: p = 0.87). CONCLUSIONS: In this study serum concentrations of antioxidants had no modifying influence on tumor response in breast cancer patients following induction radio-chemotherapy and subsequent surgery. Further studies measuring tissue levels could clarify if there is any modifying influence of antioxidants on tumor remission.

Selenium deficiency triggering intractable seizures.

Two children with severe neurodevelopmental retardation and elevated liver function tests developed intractable seizures during the first year of life. Detectable neurometabolic conditions have been ruled out. At the time of seizures evidence for systemic selenium deficiency could be documented. The youngest patient, who manifested intractable fits from the fourth day of life, died at the age of ten months. Neuropathologic examination was consistent with Progressive Neuronal Degeneration of Childhood (PNDC) with liver disease or formerly known as Alpers disease. In the oldest child, whose diet was normally balanced, fits started from the age of 11 months and features of long-standing selenium deficiency became apparent from the age of 1 1/2 years and consisted of liver function disturbances, depigmented hair and osteoarthropathy. Oral substitution with selenium supplements in both children (3-5 micrograms/kg body weight) resulted in reduction of seizures and improvement of the EEG recordings after two weeks while liver function became normal. Two of the seleno-dependent enzymes Glutathione Peroxidase (GPX) and Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPX) are speculated to play a key-role in the defence of neuronal cells against oxygen radical formation and peroxidative processes. Our findings support the hypothesis that the presence of selenium depletion in the brain amongst patients with epilepsy constitutes an important triggering factor for the origin of intractable seizures and subsequent neuronal damage.

[Objective evaluation of visual strain in computer screen and office work by recording visually evoked cortical potentials (VECP) and determining changes in contrast sensitivity and refraction]. / Untersuchungen zum objektiven Nachweis der Beanspruchung des visuellen Systems bei Bildschirm- und Büroarbeit durch Ableitung visuell evozierter kortikaler Potentiale (VECP) und Erfassung der Anderungen von Kontrastsensitivität und Refraktion.

Visual evoked cortical potentials (VECP) elicited with checkerboard pattern reversal stimuli of high spatial frequency and low contrast were recorded. The changes in the VECP depending on the duration of task-oriented activity at video display units (VDU) and in the office were determined. The testing procedure can be used to decide on adequate recovery periods (breaks) for any visual workload and requires only a short time. We investigated 30 probands: 10 subjects tested before and after 4 h of VDU work under controlled standard conditions had statistically significant increases of latency (P < 0.001) and decreases of amplitude in VECP recordings (P < 0.05). Another 10 subjects tested at the same intervals but exposed to standard office working conditions also showed statistically significant increases of latency (P < 0.0001) and decrease of amplitude in VECP recordings (P < 0.01). The 10 control subjects tested at the same intervals spent the time between recording sessions on leisure activity (walking) and showed no significant VECP changes. Statistical evaluation was performed with Student's t-test for paired samples. Contrast sensitivity (Ginsburg test) decreased in both VDU and office groups after completion of their workload, but remained within normal limits. The maximal changes in refraction amounted to +/- 0.25 D after 4 h and +/- 0.5 D after 6 h and showed no bias. Extended periods of working at VDUs and conventional office work increase the latency and decrease the amplitude of the pattern-evoked VECP. This method can be used to determine optimal scheduling of breaks in for people working at VDUs and doing conventional office work.

[Retrospective study of severe alkali burns of the eyes]. / Retrospektive Betrachtung von schweren Alkaliverätzungen der Augen.

BACKGROUND: Alkali burns are of special interest because of the rapid and deep penetration of alkali into the ocular tissues. PATIENTS AND METHODS: This report examines the epidemiology, management and outcome of 42 cases of alkali burns of the eye admitted to the eye clinic of the RWTH Aachen from 1985 to 1992. Aspects examined were the nature of accident, type of alkali, treatment and complications. The intention was to use this information for improvement of prevention and treatment of these cases. RESULTS: The age analysis showed the greatest at-risk population were the 20-40 year-old patients. 73.8% were industrial accidents, 30% happened to builders and labourers, 20% in the chemical industry and 20% in machine factories. At home most of the injuries were caused by lime and drain cleaners. Sodium and potassium hydroxide produced more extended and deeper damages than lime due to their rapid penetration through the ocular tissues. A delayed surgical intervention led to a longer time of stay in hospital and to a higher number of operations. All eyes could be prevented from melting, but an optical rehabilitation (visual acuity > 0.3) was achieved only in a few cases (14.5%). CONCLUSION: There is a need to ensure adequate public awareness of the danger of alkali burns to the eye. Beside the primary prevention, adequate first aid with immediate and continuous irrigation is of paramount importance. A uniform concept for the management of these severe cases is necessary including an antiinflammatory medical and surgical treatment.

Postmortem serum selenium concentrations and their possible etiological role in sudden infant death (SID).

The importance of selenium (Se) deficiency in the pathogenesis of human diseases such as Keshan Disease has been extensively studied. It is possible that low Se-levels could cause immunosuppression and be an etiological factor in Sudden Infant Death (SID). We investigated 50 serum samples (40 SID and 10 non-SID victims) by atomic absorption spectrometry. The results show that there is no evidence of a serum selenium deficiency in SID-victims in the region of Aachen. A relationship between selenium concentration and the infant immune system still remains speculative and 21 samples even showed increased serum levels. It could be necessary to define a 'local' normal range by examining a greater number of healthy infants.

[Chemical and thermal eye burns in the residential area of RWTH Aachen. Analysis of accidents in 1 year using a new automated documentation of findings]. / Verätzungen und Verbrennungen im Einzugsbereich der RWTH Aachen. Analyse der Unfälle über 1 Jahr mit Hilfe einer neuen automatischen Befunddokumentation.

BACKGROUND: Until now there were no statistical data on the incidence and the prevalence of eye burns. Therefore we studied all patients coming to our hospital from the area of Aachen with eye burns during the time from September 1990 until August 1991. PATIENTS AND METHODS: All patients underwent a standardized examination including special history of the burning agent, industrial medical aspects and the employers liability insurance association. The documentation of the anterior eye segment pathology was scored separately for each eye encoded by location and special items. This documentation was worked up by the aid of a database (Filemaker II). 171 patients with eye burns were documented during one year. 65 patients had both eyes burned resulting in 236 documented records. RESULTS: The 171 accidents can be divided in 104 (61%) industrial accidents and 64 (37%) housework accidents. 3 accidents were of unknown origin. Classification of burns was scored according to Reim 1991. 208 (88%) eyes showed score I burns, 27 (11.5%) score II and only one patient showed a score III eye burn. We saw 121 (70%) male patients, 39 (23%) female patients and 11 children (7%). The main age group ranged from 16-45 years. 28% (n = 30) of all accidents happened in machine factories, which have thereby in our study the highest incidence of industrial accidents. CONCLUSION: By means of a one-year statistic we found that over 60% of all eye burns were industrial accidents, 28 in machine factories and 20% in service industries. 37% houseworks accidents are very difficult to prevent because of a deficit of safety rules.