Calcium Handling Remodeling Underlies Impaired Sympathetic Stress Response in Ventricular Myocardium from Cacna1c Haploinsufficient Rats

CACNA1C encodes the pore-forming α1C subunit of the L-type Ca²⁺ channel, Cav1.2. Mutations and polymorphisms of the gene are associated with neuropsychiatric and cardiac disease. Haploinsufficient Cacna1c^+/- rats represent a recently developed model with a behavioral phenotype, but its cardiac phenotype is unknown. Here, we unraveled the cardiac phenotype of Cacna1c^+/- rats with a main focus on cellular Ca²⁺ handling mechanisms. Under basal conditions, isolated ventricular Cacna1c^+/- myocytes exhibited unaltered L-type Ca²⁺ current, Ca²⁺ transients (CaTs), sarcoplasmic reticulum (SR) Ca²⁺ load, fractional release, and sarcomere shortenings. However, immunoblotting of left ventricular (LV) tissue revealed reduced expression of Cav1.2, increased expression of SERCA2a and NCX, and augmented phosphorylation of RyR2 (at S2808) in Cacna1c^+/- rats. The β-adrenergic agonist isoprenaline increased amplitude and accelerated decay of CaTs and sarcomere shortenings in both Cacna1c^+/- and WT myocytes. However, the isoprenaline effect on CaT amplitude and fractional shortening (but not CaT decay) was impaired in Cacna1c^+/- myocytes exhibiting both reduced potency and efficacy. Moreover, sarcolemmal Ca²⁺ influx and fractional SR Ca²⁺ release after treatment with isoprenaline were smaller in Cacna1c^+/- than in WT myocytes. In Langendorff-perfused hearts, the isoprenaline-induced increase in RyR2 phosphorylation at S2808 and S2814 was attenuated in Cacna1c^+/- compared to WT hearts. Despite unaltered CaTs and sarcomere shortenings, Cacna1c^+/- myocytes display remodeling of Ca²⁺ handling proteins under basal conditions. Mimicking sympathetic stress with isoprenaline unmasks an impaired ability to stimulate Ca²⁺ influx, SR Ca²⁺ release, and CaTs caused, in part, by reduced phosphorylation reserve of RyR2 in Cacna1c^+/- cardiomyocytes.

[Study of the quality of codification of diagnoses and procedures under DRG conditions]

A system based on Diagnosis Related Groups was introduced in Germany and is mandatory for hospitals from 2004. Hospitals, health care providers and the Medical Service of Social Security-Health Insurance (MDK) face a common effort. Proper codification of diagnoses and procedures is essential. The Medical Service in the State of Hessen, the Techniker Krankenkasse and the Burgerhospital Frankfurt am Main combined forces to assess codification under the DRG system.

GOALS

The partners cooperated to assess actual codification and to identify starting points for improvement.

METHODS

A random sample was taken from all in-patient cases (all departments) over a 6-month-period (n = 309). Codification or coding was checked according to German Coding Rules (Deutsche Kodierrichtlinien) from the complete hospital records. Different codification, or coding, was discussed between MDK and Hospital doctors.

RESULTS

The actual data revealed overcoding in 34 per cent of diagnoses and in 15 per cent of procedures. Undercoding was present in 9 per cent of diagnoses and in 2 per cent of procedures. The DRG grouping changed in 68 cases (22 per cent) after scrutiny by the Medical Service (MDK). The case-mix index (CMI) calculated from relative weights as coded by the hospital was 0.84. The case-mix index calculated from coding by MDK was 0.81. The CMI calculated from effective weights was 0.77 (hospital) and 0.75 (MDK).

DISCUSSION

Causes of faulty coding and possible remedies are presented.

CONCLUSIONS

Further systematic reviews are required to develop the DRG System and identify faulty trends.

A cluster of childhood leukaemias near two neighbouring nuclear installations in Northern Germany: prevalence of chromosomal aberrations in peripheral blood lymphocytes

PURPOSE

Between 1990 and 1991 a leukaemia cluster was observed in children living close to the combined site of a nuclear power plant and a nuclear research facility in Elbmarsch, a region in Lower Saxony (Germany). We aim to investigate the prevalence of presumably radiation-induced chromosomal aberrations in peripheral blood lymphocytes of children in Elbmarsch and children of a control region in order to find out whether there was an uncontrolled release of radioactive material which resulted in a substantial exposure.

MATERIALS AND METHODS

The frequency of dicentric and ring chromosomes in lymphocytes of the peripheral blood in 42 children in Elbmarsch and 30 children in Plön was investigated. Children in both groups had been permanent residents of the study area.

RESULTS

The mean frequency of dicentric and ring chromosomes in Elbmarsch was 14/32580 cells (=0.430 x 10(-3); 95% CI 0.24-0.70 x 10(-3) cells), and in Plön it was 17/24065 cells (=0.706 x 10(-3); 95% CI 0.42-1.10 x 10(-3) cells).

CONCLUSIONS

No difference in the frequency of dicentric and ring chromosomes was observed between children in Elbmarsch living close to a combined site of a nuclear power plant and a nuclear research facility and children living in the control area Plön. The power of the study to detect a threefold or higher increase in the aberration frequency was at least 0.86.

Cytogenetic investigations in employees from waste disposal sites

In connection with extensive health studies of employees from two big central waste disposal sites, cytogenetic investigations were performed. The subject of these special analyses was to examine whether the complex mixture of pollutants from waste disposal sites comprises a genotoxic hazardous potential. Cytogenetic analyses were performed on peripheral blood lymphocytes of 82 exposed and 71 control persons as a coded study. For chromosome analysis, 1000 cells and for sister chromatid exchange (SCE) analysis, 50 cells had been scored per person. Compared with the matched control group, a highly significant increase of the frequencies of chromosomal aberrations was detected, especially in dicentric chromosomes (4.1 +/- 0.2 vs 1.5 +/- 0.1 per 1000 cells) and acentric fragments (6.9 +/- 0.3 vs 2.8 +/- 0.2 per 1000 cells), whereas no difference was found in SCE analysis. The occurrence of multiaberrant cells with more than two dicentric chromosomes was a striking feature in waste disposal site workers (23 vs 1 in control group). Frequencies of chromosomal aberrations were similar in exposed non-smokers and smokers. Only in the control group, a significant difference was observed in the incidence of dicentric chromosomes and SCE between non-smokers and smokers. The results of the first cytogenetic investigations on employees of two waste disposal sites indicate a genotoxic hazardous potential. Further research is urgently required.

Comparative biomonitoring study of workers at a waste disposal site using cytogenetic tests and the comet (single-cell gel) assay

Workers exposed to environmental pollutants at a waste disposal site were studied for genotoxic effects with cytogenetic tests and the comet (alkaline single-cell gel) assay. Analyses were performed on peripheral blood samples of 44 workers at a waste disposal site (DM) and 47 subjects of a control group (VE) matched for gender, age, and smoking habits. Chromosomal aberrations were evaluated in 1,000 lymphocytes per individual, sister chromatid exchanges in 50 cells, and DNA migration (tail moment) was determined in 100 leukocytes. Structural chromosome aberrations were more frequent in DM than in VE, but only the frequency of acentric fragments and the percentage of aberrant cells (excluding gaps) was significantly increased. No significant difference was found for the mean frequency of SCE. A statistically significant difference was also seen with the comet assay. The mean tail moment was higher in DM than in VE. However, no correlation was found between cytogenetic data and the effects in the comet assay. The results of our study indicate that DNA effects in the comet assay represent an independent endpoint which might be useful for the biomonitoring of genotoxic effects in addition to established tests.

Changes in the repair capacity of blood cells as a biomarker for chronic low-dose exposure to ionizing radiation

The purpose of this study was to examine whether changes in the repair capacity of blood cells could be used as a valuable biomarker for radiation exposure. To characterize the repair kinetics in nonirradiated and irradiated cells we first performed in vitro split dose experiments. DNA damage and DNA repair capacity were analysed using the comet assay. Our results showed that the first in vitro irradiation affects the repair system of the cells, resulting in a decreased repair capacity after the second irradiation. Furthermore, the second irradiation results in a large amount of DNA damage in the blood cells. To test whether the analysis of the DNA repair capacity after in vitro irradiation is also a valuable method for in vivo studies of donors exposed to radiation, we analysed the repair capacity of blood cells of two exposed groups: patients subjected to a radioiodine therapy and chronically irradiated volunteers from the Chernobyl region. Both groups also showed a significantly impaired repair capacity indicating a stress on the hematopoietic system. In addition, in the group of the Ukrainians DNA damage after in vitro irradiation was significantly higher than in a control group. These results lead to the presumption that the repair capacity and the DNA damage after in vitro irradiation might be a very useful biological marker for radiation exposure in population monitoring.