Early standardized clinical judgement for syncope diagnosis in the emergency department

BACKGROUND

The diagnosis of cardiac syncope remains a challenge in the emergency department (ED).

OBJECTIVE

Assessing the diagnostic accuracy of the early standardized clinical judgement (ESCJ) including a standardized syncope-specific case report form (CRF) in comparison with a recommended multivariable diagnostic score.

METHODS

In a prospective international observational multicentre study, diagnostic accuracy for cardiac syncope of ESCJ by the ED physician amongst patients ≥ 40 years presenting with syncope to the ED was directly compared with that of the Evaluation of Guidelines in Syncope Study (EGSYS) diagnostic score. Cardiac syncope was centrally adjudicated independently of the ESCJ or conducted workup by two ED specialists based on all information available up to 1-year follow-up. Secondary aims included direct comparison with high-sensitivity cardiac troponin I (hs-cTnI) and B-type natriuretic peptide (BNP) concentrations and a Lasso regression to identify variables contributing most to ESCJ.

RESULTS

Cardiac syncope was adjudicated in 252/1494 patients (15.2%). The diagnostic accuracy of ESCJ for cardiac syncope as quantified by the area under the curve (AUC) was 0.87 (95% CI: 0.84-0.89), and higher compared with the EGSYS diagnostic score (0.73 (95% CI: 0.70-0.76)), hs-cTnI (0.77 (95% CI: 0.73-0.80)) and BNP (0.77 (95% CI: 0.74-0.80)), all P < 0.001. Both biomarkers (alone or in combination) on top of the ESCJ significantly improved diagnostic accuracy.

CONCLUSION

ESCJ including a standardized syncope-specific CRF has very high diagnostic accuracy and outperforms the EGSYS score, hs-cTnI and BNP.

Prognostic significance of present atrial fibrillation on a single office electrocardiogram in patients with atrial fibrillation

BACKGROUND

Evidence for the association of atrial fibrillation (AF) present on the ECG and cardiovascular outcomes in AF patients is limited.

OBJECTIVE

To investigate the prognostic significance of AF on a single surface ECG for cardiovascular outcomes in AF patients.

METHODS

A total of 3642 AF patients were prospectively enrolled. Main exclusion criteria were rhythms other than sinus rhythm (SR) or AF. The primary end-point was a composite of all-cause death and hospitalizations for congestive heart failure (CHF). Secondary end-points were all-cause death, CHF hospitalizations, cardiovascular death, myocardial infarction, any stroke and stroke subtypes. Associations were assessed with multivariable Cox proportional hazards models.

RESULTS

Mean age was 71 years, 28% were female, and mean follow-up was 3.4 years. Patients with SR on the ECG at study enrolment (56%) were younger (69 vs. 74 years, P < 0.0001), had more often paroxysmal AF (73 vs. 18%, P < 0.0001) and fewer comorbidities. The incidence of the primary end-point was 1.8 and 3.1 per 100 person-years in patients with SR and AF, respectively. The multivariable-adjusted hazard ratio was 1.4 (95% confidence intervals 1.1; 1.7; P = 0.001) for patients with AF on the ECG compared to patients with SR. The hazard ratios (95% confidence intervals) were 1.4 (1.1; 1.8; P = 0.006) for all-cause death, 1.5 (1.2; 1.9; P = 0.001) for CHF and 1.6 (1.1; 2.2; P = 0.006) for cardiovascular death. None of the other associations were statistically significant.

CONCLUSIONS

The presence of AF in a single office ECG had significant prognostic implications with regard to mortality and CHF hospitalizations in patients with AF. These patients present a high-risk group and might benefit from intensified treatment.

Modified Acid Phosphatase Assay for Assessing the Extent of Heating of Canned Picnics and Hams: Interlaboratory Study

Determination of acid phosphatase (E.C. 3.1.3.2.) activity in meat and meat products Is based on spectrophotometric measurement of free phenol released from phenyl phosphate substrate during enzyme catalysis under prescribed conditions. Precision parameters of a new modified phosphatase assay, proposed for determination of extent of heating of canned picnics and hams, were evaluated in an interlaboratory study with 10 (1 German, 2 Italian, and 7 Hungarian) participating laboratories. The test materials were 5 lean meat batters subjected to different heat treatments (i.e., with different levels of phosphatase activity). The materials were presented to participants as 10 randomly coded samples (2 blind replicates of each material). The interlaboratory study was then repeated with 3 test materials and 2 blind replicates (3 × 2) prepared in the same way. The repeatability relative standard deviation (RSDr), outliers excluded, varied from 2.2 to 10.7%, and the reproducibility relative standard deviation (RSDR) varied from 12.6 to 25.3%. Results were compared with other data in the literature. The sensitivity of the new modified phosphatase assay was also compared with that of the original procedure described in USDA Chemistry Laboratory Guidebook. A higher sensitivity was observed for the method described in this paper. However, the method’s reproducibility was poorer than that of common analytical methods. Although high, the variability may still be acceptable for determining phosphatase activity to assess extent of heat treatment of canned picnics and hams.

The quest for indicators of paroxysmal atrial fibrillation in sinus rhythm - the DETECT AF trial

Background: Atrial fibrillation (AF) is related to an increased stroke risk. At present, differentiation between patients with paroxysmal AF (pAF) and without is only possible during AF episodes and not during sinus rhythm. If AF could be diagnosed more quickly and reliably, anticoagulation therapy may be administered and prevent from cardioembolic strokes. The DETECT AF trial evaluated the hypothesis that propagation of electric activities in patients with pAF differs from propagation in healthy atria and that this can be detected with a three-dimensional electrocardiogram in patients during sinus rhythm. Methods: We conducted a case-control study including patients with a history of pAF and a control group with no history of AF. Vectorcardiographic beat-to-beat variability of atrial activation in sinus rhythm was tested and compared between the two groups. Results: One hundred and eight patients with a history of pAF in sinus rhythm and 121 controls in sinus rhythm were included. With a combination of specific vectorcardiographic beat-to-beat variability parameters discrimination between the two groups was possible with a specificity of 82% and a sensitivity of 71% (p≤.01). Using heart rate independent parameters, both specificity and sensitivity were reduced to 70%. Conclusions: Analysis of atrial vectorcardiographic beat-to-beat variability indicates that atrial conduction variability in patients with pAF differs from patients without AF and may be used as an indicator to estimate the risk for pAF in patients during sinus rhythm. Further studies to investigate the potential of this parameter are needed. Clinical trial registration number: NCT02270112.

Different patterns of decompensation in patients with alcoholic vs. non-alcoholic liver cirrhosis

BACKGROUND

The histological pattern of fibrosis in liver cirrhosis varies in different chronic liver diseases, and hepatic decompensation may be differentiated in consequences of fibrosis (i.e. ascites, variceal bleeding) or in lack of function (i.e. jaundice) resulting in aetiology-specific variable morbidity and mortality.

AIM

To evaluate patterns of hepatic decompensation in relation to the aetiology of liver cirrhosis.

METHODS

Two different cohorts were retrospectively evaluated between 2002 and 2007. Cohort A was for hypothesis generation and consisted of 220 cirrhotic patients. To confirm the initial observations a second cohort B (n = 217) was analysed. The different patterns of hepatic decompensation evaluated were ascites, jaundice, encephalopathy, variceal bleeding, spontaneous bacterial peritonitis, hepatorenal syndrome or hepatocellular carcinoma. Furthermore, we analysed survival in relation to pattern of decompensation in alcoholic vs. non-alcoholic liver disease.

RESULTS

Alcoholics were more frequently hospitalised for ascites (cohort A: 81.4% vs. 65.4%, P = 0.016; cohort B 71.3% vs. 58.5%, P = 0.085). In contrast, non-alcoholics presented with higher rates of hepatocellular carcinoma (cohort A: 23.1% vs. 11.9%, P = 0.046; cohort B 38.6% vs. 22.5%, P = 0.018). There were no significant differences in jaundice, variceal bleeding, hepatorenal syndrome or encephalopathy. Survival was significantly impaired in non-alcoholic cirrhosis once ascites occurred (P = 0.003), whereas ascites did not predict higher mortality in patients with alcoholic cirrhosis.

CONCLUSIONS

Ascites is the leading initial pattern of decompensation in alcoholic cirrhosis whereas hepatocellular carcinoma dominates in non-alcoholics. Non-alcoholics developing ascites show a poor survival.

Characterization and financial impact of implantable cardioverter-defibrillator patients without interventions 5 years after implantation

BACKGROUND

Implantable cardioverter defibrillators (ICD's) are increasingly used for primary and secondary prevention of sudden cardiac death. However, data on how many ICD patients indeed receive appropriate ICD therapy during long-term follow-up is scarce.

AIM

The aim of our study was to determine the number of patients without appropriate ICD therapy 5 years after ICD implantation, to identify predicting factors, to assess the occurrence of late first ICD therapy and to quantify the financial impact of ICD therapy in a real-world setting.

DESIGN

Prospective observational study.

METHODS

We prospectively enrolled 322 consecutive ICD patients. Baseline data were collected at implantation and patients were followed for a median of 7.3 years (IQR 5.8-9.2 years). Time to first appropriate ICD therapy (either antitachycardia pacing or cardioversion) was documented.

RESULTS

Five years after implantation, 139 patients (43%) had not received appropriate ICD therapy. In multivariable analysis, a primary prevention indication and negative electrophysiological studies prior to ICD implantation were independent predictors of freedom from ICD therapy. Of the patients without ICD therapy, 5 years after implantation, 25% had experienced inappropriate ICD shocks. Two hundred and seven devices (1.5 devices per patient) were needed for the 139 patients without ICD intervention within 5 years, accounting for € 31,784 per patient. During an additional follow-up of 3 years, 12% of the patients with unused ICD received a late first appropriate ICD therapy.

CONCLUSION

About half of the ICD patients receive appropriate ICD therapy within 5 years after implantation. Furthermore, there is a significant proportion of patients receiving late first shocks after five initially uneventful years.

Magneto-Raman scattering of graphene on graphite: electronic and phonon excitations

Magneto-Raman-scattering experiments from the surface of graphite reveal novel features associated to purely electronic excitations which are observed in addition to phonon-mediated resonances. Graphene-like and graphite domains are identified through experiments with ∼1  μm spatial resolution performed in magnetic fields up to 32 T. Polarization resolved measurements emphasize the characteristic selection rules for electronic transitions in graphene. Graphene on graphite displays the unexpected hybridization between optical phonon and symmetric across the Dirac point inter Landau level transitions. The results open new experimental possibilities--to use light scattering methods in studies of graphene under quantum Hall effect conditions.

Specified risk material and topographical distribution of lymphoreticular tissue of the bovine tongue

The elimination of specified risk material from food is crucial to restricting the risk to public health arising from bovine spongiform encephalopathy. The distribution of lymphoreticular tissue as potential specified risk material of the bovine lingual tonsil is described in relation to topographical anatomical landmarks. The definition of a proper landmark is a prerequisite for establishing adequate legal regulations concerning the removal of the lingual tonsil after slaughter. The main parameter to identify the lymphoreticular tissue in this study was the immunohistochemical identification of the follicular dendritic cells in the lingual tonsil. Lymph nodules were detected in areas up to 30 mm rostral of a given macroscopic landmark, i.e., the most caudal of the papillae vallatae. This area must therefore be adequately removed from the bovine tongue in the slaughterhouse. The current method for the removal of the lingual tonsil tissue according to Regulation (EC) 999/2001 at the slaughterhouse and alternatives to this method are discussed.

Therapy with an implantable cardioverter defibrillator (ICD) in patients with coronary artery disease and dilated cardiomyopathy: benefits and disadvantages

Contemporary guidelines refer to ICD implantation in patients who experienced ventricular tachycardia or fibrillation as secondary prevention, and in well-defined high risk groups as primary prevention. Randomised studies were performed in patients with coronary artery disease and in non-ischaemic cardiopathies, chiefly dilated cardiomyopathy. After four years' follow-up the absolute risk reduction was some 10% in secondary prevention and 8-20% in primary prevention, depending on the patient population. As only approx. 50% of ICD patients will receive appropriate therapies during long-term follow-up, reasonable risk stratification is crucial. However, apart from ejection fraction of <35%, all other echo- or electrocardiographic factors studied have thus far failed to have significant impact to determine risk in advance. In a retrospective analysis comorbidities such as advanced age, renal failure and atrial fibrillation have been shown to influence the effect of an ICD. During long term follow-up inappropriate shocks, lead complications, premature battery depletion and anxiety are some of the most significant problems for an ICD patient.

Holter monitoring for syncope: diagnostic yield in different patient groups and impact on device implantation

BACKGROUND

Holter monitoring is routinely used in patients referred for the evaluation of syncope, but its diagnostic value in different patient groups is unclear, as is its impact on device implantation (pacemaker or cardioverter-defibrillator).

AIM

To determine the diagnostic yield of Holter monitoring in the routine evaluation of syncope, and its impact on subsequent device implantation.

DESIGN

Retrospective record review.

METHODS

We reviewed all Holter studies in patients referred with syncope between 2000 and 2005. Strict criteria were applied to determine whether a study was diagnostic. The diagnostic value of Holter monitoring (overall and in five subgroups: age, gender, structural heart disease, ejection fraction, medication) and its impact on the implantation of devices, were determined.

RESULTS

Of 4877 Holter studies, 826 were performed in patients with syncope (age 72 +/- 15 years): 71 (8.6%) were considered to explain the syncope. Structural heart disease, ejection fraction and age were significant predictors of a diagnostic study (all p < 0.01), whereas gender and cardiac medication were not. A device was implanted in 33 patients (4.4%) whose initial Holter did not explain their syncope, after mean 7 months, whereas 45 patients (5.4%) received a pacemaker based on the Holter results (p = 0.32).

DISCUSSION

The overall diagnostic yield of Holter monitoring in the evaluation of syncope was 8.6%, with dramatic differences between subgroups. Our data suggest that the impact of Holter monitoring on device implantation is generally overestimated.

Evaluation of a serological method for the detection of Taenia saginata cysticercosis using serum and meat juice samples

Two peptides, HP6-2 and Ts45S-10, were used as antigens for the detection of antibodies against Taenia saginata cysticercosis in serum and meat juice samples using enzyme-linked immunosorbent assay (ELISA). Positive control samples were obtained from animals experimentally infected (serum) and from animals naturally infected (meat juice). The two peptides and a pooled preparation of both peptides were evaluated, and their cut-off points with both sample categories were calculated. ELISA results from these different peptides were compared. Sensitivity and specificity of HP6-2 using serum were calculated as being 100 and 98%, respectively, showing to be higher than the values for the other antigens used. The average optical density (OD) value for negative samples was 0.646, whereas it was 1.702 for the positive control samples. This peptide was used to examine serum samples from animals with cysts and random field serum samples. For meat juice samples the pooled peptides showed the highest sensitivity and specificity, as they were 100 and 95%, respectively. The average OD values for the negative and the positive reference meat juice samples were 0.379 and 1.291, respectively. The optimal dilution of the meat juice samples for the ELISA was very low, as it was 1:20 using the pooled peptides, compared with 1:800 serum dilution using HP6-2. To the authors' knowledge, this is the first report of a successful testing for T. saginata cysticercosis using meat juice.

Visual diagnosis of Taenia saginata cysticercosis during meat inspection: is it unequivocal?

A total of 267 cysts were collected from March to December 2004 from two main abattoirs in northern Germany. The cysts were classified by the usual organoleptic methods during meat inspection as Cysticercus bovis. The reported prevalence of cysticercosis in the abattoirs was 0.48 and 1.08%, respectively. The cysts were examined macroscopically for description of their morphology and constituents and classified as viable or degenerating (dead). The DNA was extracted from these cysts and subjected to polymerase chain reaction (PCR) for evaluation of the detection methods used and to make certain that the cysts did indeed belong to C. bovis, as indicated at the slaughterhouses. Two sets of primers were used with different sensitivity levels. The first, HDP1, was able to detect 200 fg of Taenia saginata DNA and 100 pg of C. bovis DNA. The other primer set, HDP2, was able to detect 1 pg of T. saginata DNA and 1 ng of C. bovis DNA. No more than 52.4% of the samples tested positive for C. bovis in the PCR using both primers, while 20% of the viable cysts and 49.2% of the degenerating cysts tested negative with both primers.

[Future role of the official veterinarian at the ante- and post-mortem inspection]

The new European food hygiene legislation which will apply from 1 January 2006 on brings massive changes in the implementation of the ante- and post-mortem in-spection about. Key element in this new regulation is the introduction of a risk-based inspection of graduated intensity which in particular cases may be reduced to a document check and a visual inspection. Important changes also concern responsibility assignment between official veterinarian and official auxiliary in inspection tasks. Furthermore, the official veterinarian is assigned additional responsibility (animal welfare, animal health check). Regarding the extended competence of the official auxiliaries through the new regulation, food industry is requiring a diminution of the inspection costs. In this article, the future scope of duties of the official veterinarian at the ante- and post-mortem inspection is presented, as well as the practical consequences the implementation of the new meat hygiene regulation will have.

[Do we need pathogen-free livestock for food safety?]

The reduction of the entry of pathogens in the food chain is an important premise in improving the safety of food of animal origin. Since food animals are the main reservoir for pathogens, the prevalence of pathogens in livestock is of great importance. Unfortunately, classical measures to improve animal health can not exclude the presence of the main food-borne zoonotic agents (Salmonella, Campylobacter, Listeria monocytogenes, verotoxinogene Escherichia coli, Toxoplasma gondii) in "clinically healthy" animals. Absence of pathogens in livestock must be regarded as an unrealistic aim. To achieve an effective improval of product safety through logistical, hygienic or technological measures both farmers and food producers need valid data about the prevalence of pathogens in livestock, in each animal and in raw material of animal origin, respectively. Yet available data are insufficient. New European directives and regulations concerning monitoring and control of zoonosis demand the systematic control of presence of zoonotic agents in livestock and later steps of the food chain.

Effects of aging prior to freezing on poultry meat tenderness

The objective of this study was to investigate the effects of aging prior to deboning and deep-freezing on the tenderness of cooked broiler breast fillets. Broilers (Ross-208) that were 37 and 38 d old were slaughtered in a licensed poultry meat plant. After spray chilling, carcasses with BW between 1,080 and 1,300 g were selected for the study and transported to a chilling room (2 to 4 degrees C). The whole carcasses were aged for up to 24 h. During the aging process, continuous measurements were made of pH values, electric conductivity, and firmness of the raw fillets. After the aging process, the carcasses were deboned, and the breast fillets were immediately frozen to an internal temperature of -20 degrees C. Tenderness was measured both mechanically with a Warner-Bratzler shear force device and by sensory testing. The ultimate pH values in the fillets were reached during the first 5 h of aging. Electric conductivity increased during the whole aging period. During the first hours of aging, firmness increased significantly, corresponding with the onset of rigor mortis. After between 8 and 9 h of aging, firmness decreased significantly. Shear force values of aged fillets also changed significantly; the highest values were found at the beginning of aging, which then decreased from the sixth hour. The results of the instrumental tenderness measurements were confirmed by the sensory evaluations. Implementation of in-plant measurements of firmness, thus, seemed to be useful in predicting the sensory quality of poultry meat.

Shortening of the Bovine Tongue According to Regulation (EC) 999/2001 is not Complying with the Current Legal Definition of Specified Risk Material - a Macroscopical and Histological Preliminary Study

The full elimination of all specified risk material (SRM) in food of animal origin is crucial for consumer protection and is of high priority in inner EU trade. Among other tissues, the tonsils of cattle are considered as SRM. The aim of this study was to evaluate whether the 'cut at the back of the tongue just before the tongue bones' required by EC regulation is sufficient to remove tonsils and lymphatic tissue completely. Eight skulls from cattle were collected for the simulation of a vertical cut according to the EC regulation and the detection of the target at the back of the tongue. Further, specimens of the lingual mucosa were cut out from two tongues and examined microscopically. The most caudal of these specimens was from the macroscopically visible part of the lingual tonsil. The most rostral specimen contained the most caudal Papilla vallata. Simulation of the obligatory ventro-dorsal cut yielded hits at varying locations on the dorsal surface of the tongue, sometimes including tissue of the lingual tonsil. Histological examination of the lingual mucosa gave clear evidence that lymphatic tissue resembling the tissue of a tonsil in terms of its histological organization and infiltration of the mucosal epithelium could even be found in areas with no macroscopically visible lingual tonsils.

[Parasites in meat: a challenge for veterinarians in meat hygiene]

Meat hygiene is an important instrument of preventive public health since the end of the nineteenth century. The methods used during ante-mortem and post-mortem inspection are partly quite traditional. This is in particular true for the identification of parasites in meat. The aim of this review was to present facts on aetiology, prevalence and importance of meat-borne parasitic hazards. The capacity and the limits of the ante-mortem and post-mortem inspection for the identification of parasitic hazards are considered. Further, suggestions for the improvement of the meat hygiene are given. Cysticercosis, Toxoplasmosis and Sarcocystosis are exposed in detail. With regard to Cysticercosis, the integration of serological methods in the inspection procedure could result in a tenfold improvement of diagnostical sensitivity. With regard to Toxoplasmosis, it is obvious that meat containing Toxoplasma-cysts may reach the consumer, as animals infected with Toxoplasma gondii can neither be recognised in the ante-mortem inspection nor in the meat inspection. Systematical serological investigations on farm level would allow an appropriate judgement during meat inspection and minimize the consumer exposure to this parasite. Further, reliable methods for the detection of Toxoplasma-cysts have to be developed. With regard to Sarcocystosis, the compulsory inspection of the muscle surfaces to recognise a "massive infection with Sarcocystis" is very doubtful in its interpretation. There is a need for suitable microscopic, serological and molecular biological methods for the detection of Sarcocystis-species and reliable informations on the seroprevalence of the parasite in slaughtering animals.

Physical and biological parameters affecting DNA double strand break misrejoining in mammalian cells

In an attempt to investigate the effect of radiation quality, dose and specific repair pathways on correct and erroneous rejoining of DNA double strand breaks (DSBs), an assay was applied that allows the identification and quantification of incorrectly rejoined DSB ends produced by ionising radiation. While substantial misrejoining occurs in mammalian cells after high acute irradiation doses, decreasing misrejoining frequencies were observed in dose fractionation experiments with X rays. In line with this finding, continuous irradiation with gamma rays at low dose rate leads to no detectable misrejoining. This indicates that the probability for a DSB to be misrejoined decreases drastically when DSBs are separated in time and space. The same dose fractionation approach was applied to determine DSB misrejoining after alpha particle exposure. In contrast to the results with X rays, there was no significant decrease in DSB misrejoining with increasing fractionation. This suggests that DSB misrejoining after alpha irradiation is not significantly affected by a separation of particle tracks. To identify the enzymatic pathways that are involved in DSB misrejoining, cell lines deficient in non-homologous end-joining (NHEJ) were examined. After high X ray doses, DSB misrejoining is considerably reduced in NHEJ mutants. Low dose rate experiments show elevated DSB misrejoining in NHEJ mutants compared with wild-type cells. The authors propose that NHEJ serves as an efficient pathway for rejoining correct break ends in situations of separated breaks but generates genomic rearrangements if DSBs are close in time and space.

Tetracycline residues in meat and bone meals. Part 2: the effect of heat treatments on bound tetracycline residues

The stability of bound tetracycline residues during heat treatments at 133 degrees C and 100 degrees C for up to 45 min was investigated. An intermediate product from a rendering plant was mixed with bone splinters that contained bound tetracycline (TC) and chlortetracycline (CTC) residues. The mixture was heated in an autoclave at 133 degrees C for 20, 30 and 45 min and at 100 degrees C for 20 and 30 min and subsequently dried at 103 degrees C for 4 h. Two different extraction procedures with hydrochloric acid were used, one with and one without the previous sedimentation of bone particles. Tetracycline concentrations were determined by HPLC analysis before and after the heat treatment. A complete destruction of tetracyclines during heat treatment at 133 degrees C could not be demonstrated, but there was a significant decrease of TC by about 50%. CTC was less resistant to the same temperature, which brought about a reduction of 90-100%. Treatment at 100 degrees C did not bring about any reduction, except for CTC after extraction without sedimentation. The possible toxicological relevance of the findings is discussed. Further research has to be done on possible degradation products of the tetracycline derivatives.

Radiation-induced genomic rearrangements formed by nonhomologous end-joining of DNA double-strand breaks

Two major pathways for repairing DNA double-strand breaks (DSBs) have been identified in mammalian cells, nonhomologous end-joining (NHEJ) and homologous recombination (HR). Inactivation of NHEJ is known to lead to an elevated level of spontaneous and radiation-induced chromosomal rearrangements associated with an increased risk of tumorigenesis. This has raised the idea of a caretaker role for NHEJ. It is, however, not known whether NHEJ itself can also cause rearrangements. To investigate, on the DNA level, the influence of a defect in NHEJ on the formation of genomic rearrangements, we applied an assay based on Southern hybridization that allows the identification and quantification of incorrectly rejoined DSB ends produced by ionizing radiation. After 80 Gy of X-irradiation at a high dose rate (23 Gy/min), wild-type cells repaired 50% of the induced DSBs within 24 h by incorrect rejoining. This frequency of DSB misrejoining is considerably reduced in NHEJ-deficient cells. Low-dose-rate experiments, in which the cells were exposed to 80 Gy over a period of 14 days under repair conditions, led to no detectable misrejoining in wild-type cells but revealed a misrejoining frequency of 10% in NHEJ-deficient cells. This shows that in situations of separated breaks, NHEJ deficiency leads to genomic rearrangements, in agreement with chromosomal studies. However, if multiple DSBs coincide, even wild-type cells form genomic rearrangements frequently. These repair events are absent in Ku80-, DNA-PKcs-, and DNA ligase IV-deficient cells but are present in RAD54(-/-) cells. This strongly suggests that NHEJ has, in addition to its caretaker role, also the potential to effect genomic rearrangements. We propose that it serves as an efficient pathway for rejoining correct break ends in situations of separated breaks but generates genomic rearrangements if DSBs are close in time and space.

Tetracycline residues in meat and bone meals. Part 1: methodology and examination of field samples

The incidence of tetracycline residues in commercially available samples of meat meals and meat and bone meals was investigated. Four different methods were used on each of the 87 samples from nine different rendering plants in Germany: examination using a screening fluorescence test; examination by high performance liquid chromatography analysis using three different extraction procedures (succinate buffer, hydrochloric acid, hydrochloric acid after sedimentation of bone particles). Tetracyclines were found in 100% of the samples by one or more of the extraction procedures. The highest concentrations found in meat meals were 2048 microgkg(-1), 1393 microgkg(-1) and 608 microgkg(-1) for oxytetracycline, tetracycline and chlortetracycline, respectively. In meat and bone meals the highest concentrations were 2295 microg oxytetracycline kg(-1) 848 microg tetracycline kg(-1) and 1274 microg chlortetracycline kg(-1). The extraction after sedimentation was the most effective of the applied extraction procedures and exposed the highest total tetracycline concentrations. The results of this investigation showed that considerable amounts of tetracyclines have to be expected in field samples. Further research has to be done on the heat stability of bound tetracycline residues.

Stability of tetracycline in water and liquid manure

The objective of this study was to establish a suitable model for the prediction of the environmental stability of antibiotics in water and liquid manure. The model consists of incubation systems for solutions with installations for stirring ventilation. It was used to examine the stability of tetracycline in ventilated and unventilated Ringer's solution and liquid pig manure for a period of 8 days. Tetracycline concentrations decreased significantly during the experiment. The fastest degradation was observed in ventilated liquid manure. The test might be used as a screening test for the determination of the degradation half-life of antibiotics in the first phase of an environmental safety study according to directive 92/18/EEC.

No dose-dependence of DNA double-strand break misrejoining following alpha-particle irradiation

PURPOSE

To investigate whether an explanation for the high effectiveness of densely ionizing radiation with regard to complex biological endpoints can be derived from measurements of radiation-induced double-strand break (DSB) misrejoining.

MATERIALS AND METHODS

Misrejoining of radiation-induced DSB in normal human fibroblasts was determined by comparing hybridization analysis of large restriction fragments as a measure for correct rejoining, with results from a conventional pulsed-field gel electrophoresis technique (FAR) that measures total DSB rejoining. In order to investigate DSB misrejoining at doses for which chromosome aberration data are available, a dose fractionation protocol was applied so that the number of DSB at any given timepoint was low but the cumulative amount of misrejoined DSB sufficient for detection and precise quantitation.

RESULTS AND CONCLUSION

After an acute 80Gy alpha-particle exposure and a repair incubation period of 24 h, 50% of all initially induced DSB were misrejoined, in agreement with data obtained for X-rays. X-irrradiation with 16 x 5 Gy, 8 x 10 Gy, 4 x 20 Gy, or 2 x 40 Gy and repair incubation of 24 h following each individual dose fraction was recently reported to yield misrejoining frequencies that strongly decrease with increasing fractionation (Löbrich et al. 2000; Genes, Chromosomes and Cancer, 27, 59-68). In the present study, constant misrejoining frequencies of 50% were observed after alpha-particle exposure with the same fractionation protocol. This difference between alpha-particles and X-rays is in accordance with the high biological effectiveness of densely ionizing radiation and provides a direct link between misrejoining of DSB and cytologically visible exchange aberrations. Further evidence suggests that if the same dose range is compared, the number of misrejoined DSB exceeds the number of microscopically visible aberrations by an order of magnitude for both radiation types, probably reflecting the high resolution of the hybridization approach compared with cytological techniques.

Joining of correct and incorrect DNA double-strand break ends in normal human and ataxia telangiectasia fibroblasts

Chromosomal aberrations are believed to result from the incorrect joining of DNA double-strand breaks (DSBs). In an attempt to investigate induction and rejoining quality of DSBs following ionizing radiation exposure in specific genomic locations of mammalian DNA, an experimental approach based on Southern hybridization of single-copy probes to NotI restriction fragments was developed. Induction of DSBs is measured from the decrease of the band intensity representing the unbroken restriction fragment. An increase in intensity of the hybridization band following repair incubation determines reconstitution of the original restriction fragment and thus rejoining of correct DNA ends. We investigated the dose dependence of DSB misrejoining using X-ray doses of 5, 10, 20, 40, and 80 Gy and provide evidence that the number of misrejoined DSBs exceeds, for the same doses used, the number of cytogenetically visible aberrations by an order of magnitude, reflecting the higher resolution of our assay. Induction of DSBs and joining of correct and incorrect break ends were further investigated in cells from a patient with the cancer-prone disease ataxia telangiectasia (AT) and in heterozygous AT cells. We found, compared to normal cells, identical induction rates and identical kinetics for joining correct ends following an 80-Gy X-ray exposure. After 5 and 10 Gy, however, AT homozygotes showed a 50% elevation in the proportion of breaks that are not correctly rejoined. These data indicate a defect in the accuracy of DSB rejoining in AT cells that may account for radiation sensitivity and the occurrence of the high level of chromosomal aberrations observed in AT cells. Genes Chromosomes Cancer 27:59-68, 2000.

Assignment of linkage groups to pea chromosomes after karyotyping and gene mapping by fluorescent in situ hybridization

Chromosomes of the pea (Pisum sativum L.) were submitted to fluorescent in situ hybridization (FISH) with probes specific for the oligonucleotides (AG)12, (AC)12, (GAA)10, and (GATA)7 and for the genes encoding 25S rRNA, 5S rRNA and the storage proteins legumin A, K and vicilin. A fourth 5S rRNA gene locus, apparently specific for an accession of the cultivar Grüne Victoria, was newly detected. This allowed all seven chromosome pairs to be distinguished by FISH signals of rRNA genes. The same was possible using a combination of oligonucleotide probes or of oligonucleotides and rRNA gene-specific probes in multicolour FISH. Rehybridization with the 5S rRNA gene-specific probe allowed us to assign vicilin genes to the short arm of chromosome 5, the single legumin A locus to the long arm of chromosome 3 and the legumin B-type genes (exemplified by legumin K) to one locus on the short arm of chromosome 6. Correlation of these data with an updated version of the pea genetic map allowed the assignment of most linkage groups to defined chromosomes. It only remains to be established which of linkage groups IV and VII corresponds to the satellited chromosomes 4 or 7, respectively.

Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO

The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard.

Determination of absolute emission cross sections for electron-impact-induced line radiation in the vacuum ultraviolet

A method and an experimental setup have been developed for measuring absolute photoemission cross sections for electron-impact-induced line radiation in the vacuum ultraviolet (VUV). Unparalleled low uncertainties for the cross sections were achieved mainly from the use of the Berlin electron storage ring as a primary standard source in the VUV for the determination of the responsivity of the spectrometer-detector system used and from the use of a spinning rotor gauge as a secondary standard for the determination of the target gas density. As the first result we present a photoemission cross section for the Ar II 3s3p(6)(2)S(½)-3s(2)3p(5)(2)p?(3/2) transition at 91.98 nm for 2-keV electron-impact energy of 1.167 × 10(-18) cm(2) with a relative uncertainty of 4.4% (√3σ value). This low uncertainty demonstrates the suitability of the setup for further cross-section measurements.

Radiometric characterization of a Penning discharge in the vacuum ultraviolet

We present a Penning discharge as a possible radiometric transfer standard source in the vacuum UV, primarily in the spectral region below 20 nm. Following the concept of Finley et al., we have designed a Penning source using NdFeB permanent magnets. Emphasis was put on simple operation, quick electrode exchangeability, and easy source readjustment. The radiant intensities of the emission lines from different ionization stages of both buffer gas atoms and atoms sputtered from the cathodes have been studied in various discharge conditions. For selected Al and buffer gas emission lines we determined the absolute radiant intensities by a comparison with the calculable spectral radiant power of the Berlin Electron Storage Ring. A comparison with data from our hollow-cathode transfer standard source is given.

Tungsten/Magnesium silicide multilayers for soft x-ray optics

W/Mg2Si multilayers for soft x-ray optics above the MgKα and MgLα lines have been deposited by RF sputtering. Their structural characteristics have been deduced from in situ kinetic ellipsometry, ex situ grazing x-ray reflection measurements, and high-resolution electron microscopy. Their soft x-ray performances have been measured by synchrotron radiation around the MgKα and MgLα lines and related to the structural characteristics. For short wavelengths, first Bragg peak reflectivities as high as 31% have been measured for multilayers with double period equal to 84 Å. For samples with smaller layer thicknesses, these performances decrease due to finite interdiffusion at the interfaces. Nevertheless, well-defined Bragg peaks are observed even when the double period is as low as 44 Å. Near the MgLα line, more than 20% reflectivity at the first Bragg peak has been measured at normal incidence. At the same wavelength the selectivity is two times higher than that of conventional systems such as Mo/Si.

Characterization of pinhole transmission gratings

Gold pinhole transmission gratings fabricated by Heidenhain GmbH primarily for the purpose of studying the radiation of intense soft x-ray sources have been tested with the synchrotron radiation of BESSY. Typical results for the spectral dependence of the grating efficiency into the various diffraction orders are presented in a wavelength region ranging from 4 to 20 nm. Also the influence of grating irregularities has been studied. With appropriate grating parameters quite good agreement between the experimental results and theoretical Calculations is Obtained.

High current hollow cathode as a radiometric transfer standard source for the extreme vacuum ultraviolet

A high current hollow cathode source has been developed as a radiometric source standard for the extreme VUV. The source is operated at a constant current of 2 A with an aluminum cathode and helium or argon as buffer gas at pressures of ~1 hPa. The radiance of spectral lines in the wavelength range from 13 to 60 nm has been determined by comparison to the calculable spectral radiant power of the electron storage ring BESSY. An uncertainty of the order of 13% has been achieved for most of the investigated lines. The spectral emission is stable to better than 5% for an operating time of 30 h. An exchange of the cathode restores the original radiance.

Soft x-ray radiation from laser-produced plasmas: characterization of radiation emission and its use in x-ray lithography

Laser pulses of 15 ns and </=3 J at 1064nm and </=1.2 J at 532 nm were focused onto steel targets to produce plasmas emitting intense soft x-ray radiation pulses. The plasma generation is described, and the x-ray emission is spectrally and spatially characterized. Using this plasma as an x-ray source, FBM120 resist was exposed through a gold patterned 2-microm silicon mask. Exposing the same resist to a primary standard source (electron storage ring BESSY) the plasma x-ray emission was evaluated resulting in conversion efficiencies (laser into x-ray radiation) of up to 3.4% for 1064 nm and up to 5.0% for 532-nm laser radiation pulses.

Demonstration of guided-wave phenomena at extreme-ultraviolet and soft-x-ray wavelengths

We report an explicit demonstration of classical guided-wave propagation at XUV and soft-x-ray wavelengths. Experiments were performed using narrow-band synchrotron radiation at 5, 20.8, 21, and 30 nm. Free-standing gold transmission gratings served as waveguide structures. These structures had a 300-nm grating period with waveguide channel widths as small as 100 nm and were as thick as 700 nm in the direction of guided-wave transmission. Guided-wave phenomena were manifest in strongly asymmetric diffraction patterns resulting from the angular tilt of the transmission-grating normal from the incident-beam direction.

Spectral radiant power measurements of VUV and soft x-ray sources using the electron storage ring BESSY as a radiometric standard source

A method is described for measuring the spectral radiant power of VUV and soft x-ray sources using the electron storage ring BESSY as a radiometric standard source of calculable spectral radiant power and degree of polarization. An ellipsoidal grazing incidence mirror stigmatically images the stored electrons or the source under investigation in equal optical conditions into a toroidal grating monochromator. The monochromator can be rotated around its optical axis in UHV conditions to account for different degrees of polarization of the two sources. The accuracy presently available with this method is demonstrated by a measurement of the spectral concentration of radiant intensity of a laser-produced tungsten plasma in the wavelength range between 7 and 100 nm with an overall uncertainty of 10%. A detailed analysis of the contributions to this uncertainty shows that the major part of it is caused by the presently uncertain knowledge of the polarizing properties of the radiometric instrumentation and by the uncertainty of the correction procedure which accounts for the influence of higher diffraction orders of the monochromator grating. The results of the radiation measurements of the laser-produced tungsten plasma let us expect that this source type has the potential to serve as a radiometric transfer standard in the VUV and soft x-ray range below 100 nm.

Soft-x-ray generation in a helium environment using laser-produced plasmas

Soft-x-ray radiation was generated by focusing the beam of a Q-switched Nd:glass laser on a steel target in a chamber filled with He at pressures of 10(-5)mbar </= p </= 500 mbar. The radiation at lambda </= 1.5 nm was detected using a P-I-N diode behind a 25-microm Be foil. For He pressures p <100 mbar and laser pulse energies </=2 J, the soft-x-ray emission of the laser-produced plasma was reduced by less than 10% compared with the emission under high-vacuum conditions. The half-width tau(x-ray) of the soft-x-ray emission time was independent of p and of the same order as the laser pulse half-width tau(LASER) asymptotically equal to 17 nsec.

BRV-continuum source as a radiometric transfer standard between 40 nm and 600 nm

The BRV-continuum source was investigated for its potential use as a radiometric transfer standard in the wavelength region from 40 to 600 nm. Variations of the spectral radiance from one pulse to the other up to a factor of 3 are possible, but the mean value of more than 15 pulses in general is reproducible within 15%. The time-integrated spectral radiance of the pulses shows a wavelength dependence proportional to lambda(-2.5) for lambda > 100 nm and is proportional to lambda(-2.1) around 50 nm.