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Biomedical subjects

C Johannes

Publications and source records attributed to C Johannes.

At least 19 recordsLinked to original sources
PubMed2005

Space radiation does not induce a significant increase of intrachromosomal exchanges in astronauts' lymphocytes.

Chromosome aberration analysis in astronauts has been used to provide direct, biologically motivated estimates of equivalent doses and risk associated to cosmic radiation exposure during space flight. However, the past studies concentrated on measurements of dicentrics and translocations, while chromosome intrachanges (inversions) have never been measured in astronauts' samples. Recent data reported in the literature suggest that densely ionizing radiation can induce a large fraction of intrachanges, thus leading to the suspicion that interchanges grossly underestimate the cosmic radiation-induced cytogenetic damage in astronauts. We have analyzed peripheral blood lymphocytes from 11 astronauts involved in short- or long-term space flights in low-Earth orbit using high-resolution multicolor banding to assess the frequency of intrachromosomal exchanges in both pre- and post-flight samples. We did not detect any inversions in chromosome 5 from a total of 2800 cells in astronauts' blood. In addition, no complex type exchanges were found in a total of 3590 astronauts' lymphocytes analyzed by multifluor fluorescence in situ hybridisation. We conclude that, within the statistical power of this study, the analysis of interchanges for biological dosimetry in astronauts does not significantly underestimate the space radiation-induced cytogenetic damage, and complex-type exchanges or intrachanges have limited practical use for biodosimetry at very low doses.

Astronauts↗
PubMed2005

Chromosomal intrachanges induced by swift iron ions.

We measured the induction of structural aberrations in human chromosome 5 induced by iron ions using the novel technique of multicolor banding in situ hybridization (mBAND). Human lymphocytes isolated from whole blood were exposed in vitro to 500 MeV/n (LET=200 keV/micrometers, doses 1 or 4 Gy) Fe nuclei at the HIMAC accelerator in Chiba (Japan). Chromosomes were prematurely condensed by calyculin A after 48 h in culture and slides were painted by mBAND. We found a frequency of 0.11 and 0.57 residual breakpoints per chromosome 5 after 1 and 4 Gy Fe-ions, respectively. Inter-chromosomal exchanges were the prevalent aberration type measured at both doses, followed by terminal deletions, and by intra-chromosomal exchanges. Among intra-chromosomal exchanges, intra-arm events were more frequent than inter-arm, but a significant number of intra-changes was associated to inter-changes involving the same chromosome after 4 Gy of iron ions. These events show that the complexity of chromosomal exchanges induced by heavy ions can be higher than expected by previous FISH studies.

Chromosome Aberrations↗
PubMed2004

Chromosome intrachanges and interchanges detected by multicolor banding in lymphocytes: searching for clastogen signatures in the human genome.

Genomic fingerprints of mutagenic agents would have wide applications in the field of cancer biology, epidemiology and prevention. The differential spectra of chromosomal aberrations induced by different clastogens suggest that ratios of specific aberrations can be exploited as biomarkers of carcinogen exposure. We have tested this hypothesis using the novel technique of multicolor banding in situ hybridization (mBAND) in human peripheral blood lymphocytes exposed in vitro to X rays, neutrons, heavy ions, or the restriction endonuclease AluI. In the heavy-ion-irradiated cells, we further analyzed aberrations in chromosome 5 using multicolor FISH (mFISH). Contrary to the expectations of biophysical models, our results do not support the use of the ratios of inter-/intrachromosomal exchanges or intra-/interarm intrachanges as fingerprints of exposure to densely ionizing radiation. However, our data point to measurable differences in the ratio of complex/simple interchanges after exposure to different clastogens. These data should be considered in current biophysical models of radiation action in living cells.

Biomarkers↗
PubMed2002

Chromosomal aberrations: formation, identification and distribution.

Chromosomal aberrations (CA) are the microscopically visible part of a wide spectrum of DNA changes generated by different repair mechanisms of DNA double strand breaks (DSB). The method of fluorescence in situ hybridisation (FISH) has uncovered unexpected complexities of CA and this will lead to changes in our thinking about the origin of CA. The inter- and intrachromosomal distribution of breakpoints is generally not random. CA breakpoints occur preferentially in active chromatin. Deviations from expected interchromosomal distributions of breakpoints may result from the arrangement of chromosomes in the interphase nucleus and/or from different sensitivities of chromosomes with respect to the formation of CA. Telomeres and interstitial telomere repeat like sequences play an important role in the formation of CA. Subtelomeric regions are hot spots for the formation of symmetrical exchanges between homologous chromatids and cryptic aberrations in these regions are associated with human congenital abnormalities.

Animals↗
PubMed2000

Digit preference in year at menopause. Data from the study of women's health across the nation.

PURPOSE: To assess possible digit preference in self-reported year at natural menopause, and to determine whether equal proportions is an appropriate reference distribution.METHODS: Data are from the cross-sectional telephone interview from the Study of Women's Health Across the Nation (SWAN), a multi-site, multi-ethnic study of women aged 40-55. Analyses included 2151 naturally menopausal respondents, who were asked the year their periods stopped. Using a chi-square test, we compared the distribution of the terminal digit for year of final menstrual period (FMP) to an equal proportions (EP) distribution assigning 10% probability of each of the 10 digits. Departures from EP, however, may be accurate and may reflect the observed age distribution of subjects rather than digit preference. Thus, we stratified by year of interview to determine if the distribution was the same across years-suggesting digit preference-or if it varied systematically. We then estimated an expected distribution of terminal digit for year of FMP, using prospectively collected data (not subject to digit preference or recall bias) from the Massachusetts Women's Health Study, applied to the SWAN age distribution. The SWAN terminal digit distribution was compared with this expected distribution.RESULTS: Terminal digit for year at FMP exhibited a strong departure from EP (chi(2) = 841.60, p < 0.001), with highest frequencies for digits 4 and 5. Stratifying by year of interview, the distribution was shifted one digit in 1997 compared with 1996, consistent with unbiased reporting. Using the expected distribution as the reference reduced the chi-square statistic by a factor of 7 (chi(2) = 119.51, p < 0.001).CONCLUSIONS: The distribution of terminal digits for reported year at FMP was far from uniform, but departures from EP were consistent with results expected from an independent prospective study. These results suggest that EP may not be an appropriate reference for studies of digit preference, particularly those with a restricted age range.

Journal Article↗
PubMed2000

Electronic versus paper instruments for daily data collection.

PURPOSE: Collecting daily information on a series of similar, recurring events such as menstrual bleeding, headaches, or insulin levels using paper instruments is subject to problems such as missing or incorrectly recorded data, and retrospective data entry. The authors are developing and evaluating electronic data collection using hand-held personal computers (H/PC) for a variety of health-related applications, including tracking premenstrual syndrome (PMS), fertility awareness, and headaches, to improve accuracy and timeliness of data collection.METHODS: ProCycle is a prototype electronic diary for collection of daily data on menstrual bleeding, medications, and health symptoms. In a 3-month pilot test in 25 regularly cycling women, we compared its performance with a paper calendar regarding missing and incorrect data, data entry lag, data cleaning time, and users' preferences with respect to factors such as remembering to enter data, convenience, and overall preference. Additional programs for PMS, fertility, and headaches are being field tested on subjects from the Boston and New York areas, comparing performance with paper versions.RESULTS: In the pilot test, missing data occurred less frequently with ProCycle than with paper, particularly for any days with missing symptoms (4% vs. 35%, p < 0.05). ProCycle did not permit any data recording mistakes such as circling contradictory responses (e.g., bleeding and no bleeding), compared with incorrect data on 13% of paper calendars. Data entry/cleaning time was 81% lower for ProCycle. 70% of users preferred ProCycle overall, compared with 9% preferring paper (p < 0.01).CONCLUSIONS: Although the initial cost of the H/PC is significantly higher than paper, there are no recurring charges for printing or data entry, and data cleaning is minimal. Electronic instruments on an H/PC provide an efficient, accurate method of data collection, applicable to a number of areas of health-related research involving daily data collection.

Journal Article↗
PubMed2000

Radical mediated indirect oxidation of a PEG-coupled polycyclic aromatic hydrocarbon (PAH) model compound by fungal laccase.

A high molecular model compound of polycyclic aromatic hydrocarbon was synthesised by coupling pyrene to PEG(5000). The pyrene-PEG was used for the study of a laccase-mediator-system. To prevent direct contact between the substrate and the enzyme the two were kept in their own compartments separated by a membrane. The low molecular mediators, 1-hydroxybenzotriazole and 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid), which were oxidised by laccase to the corresponding radicals or cations permeated the membrane and reacted with the pyrene-PEG model compound. Oxidation of the model compound resulted in an alpha-oxidation of the alkyl-chain leading to two main oxidation products. The same oxidation products were obtained in the reaction system without a membrane.

Chromatography, High Pressure Liquid↗
PubMed2000

Laccase activity tests and laccase inhibitors.

Sulfhydryl organic compounds described as laccase inhibitors: dithiothreitol, thioglycolic acid, cysteine, diethyldithiocarbamic acid, and sodium azide were tested for their activity toward laccase of Trametes versicolor in different test systems utilising 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2, 6-dimethoxyphenol as enzyme substrates. Only sodium azide acted as a true laccase inhibitor and showed no significant interference with the enzyme tests. All other substances did not significantly inhibit the laccase activity and the previously reported inhibitory effects result from the reductions of the reaction products such as ABTS radical cation and diquinone or subsequent non-enzymatic interactions during substrate oxidation. The latter apparently forms a complex with unreacted ABTS displaying varied spectral characteristics and resulting in an underestimation of enzyme activity.

Benzothiazoles↗
PubMed2000

Natural mediators in the oxidation of polycyclic aromatic hydrocarbons by laccase mediator systems.

The oxidation of polycyclic aromatic compounds was studied in systems consisting of laccase from Trametes versicolor and so-called mediator compounds. The enzymatic oxidation of acenaphthene, acenaphthylene, anthracene, and fluorene was mediated by various laccase substrates (phenols and aromatic amines) or compounds produced and secreted by white rot fungi. The best natural mediators, such as phenol, aniline, 4-hydroxybenzoic acid, and 4-hydroxybenzyl alcohol were as efficient as the previously described synthetic compounds ABTS [2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] and 1-hydroxybenzotriazole. The oxidation efficiency increased proportionally with the redox potentials of the phenolic mediators up to a maximum value of 0.9 V and decreased thereafter with redox potentials exceeding this value. Natural compounds such as methionine, cysteine, and reduced glutathione, containing sulfhydryl groups, were also active as mediator compounds.

Amines↗
PubMed1999

Influence of sodium butyrate on the induction of radiation-induced chromosomal aberrations and sister chromatid exchanges in Chinese hamster ovary (CHO) cells.

CHO cells were pre-treated with sodium butyrate (SB) for 24 h and then X-irradiated in G1. Metaphases were scored for the induction of chromosomal aberrations and sister chromatid exchanges (SCEs). The data were compared with those obtained after irradiation of cells not pre-treated with SB and showed that SB has different effects on the endpoints examined. The frequencies of dicentric chromosomes were elevated and of small acentric rings (double minutes, DMs) reduced. These results are discussed to be a consequence of conformational changes in hyperacetylated chromatin which could lead to more interchromosomal and to less intrachromosomal exchanges. SB itself induces a few SCEs but suppresses the induction of SCEs by X-rays. We assume that a minor part of radiation induced SCEs are 'false' resulting from structural chromosomal aberrations, such as inversions, induced in G1. Inversions are the symmetrical counterparts of DMs. If inversions are suppressed by SB treatment to a similar extent as DMs a small reduction of SCEs by SB can be expected.

Animals↗
PubMed1999

Analysis of X-ray-induced aberrations in human chromosome 5 using high-resolution multicolour banding FISH (mBAND).

Peripheral lymphocytes were exposed to 4 Gy X-rays and aberrations were analysed in human chromosome 5 using high-resolution multicolour banding fluorescence in-situ hybridization (mBAND). This method is suited to detect simple and complex aberrations including peri- and paracentric inversions and exchanges between both chromosomes 5. Additionally, breakpoints carr be assigned to specific regions in chromosome 5. Quantitative relationships of induced aberration types are discussed.

Chromosome Aberrations↗
PubMed1999

Manned missions to Mars and chromosome damage.

PURPOSE: To estimate the frequencies of dicentric chromosomes in peripheral lymphocytes of astronauts on missions to Mars. MATERIALS AND METHODS: Calculations of expected frequencies of dicentrics are based on dose estimations and lymphocyte biology. RESULTS: Frequencies of dicentrics are predicted to be 10-40 times higher than the background level. CONCLUSIONS: Stressing the importance of careful mission planning and optimized shielding of transfer vehicle to Mars.

Astronauts↗
PubMed1997

Malignant transformation by cyclin E and Ha-Ras correlates with lower sensitivity towards induction of cell death but requires functional Myc and CDK4.

We demonstrate in this paper that the G1 phase specific cell cycle regulator cyclin E is able to provoke focus formation when cotransfected with activated Ha-ras into primary rat embryo fibroblasts (REFs). Cyclin E/Ha-ras transformed cells are highly tumorigenic in synergeneic rats, are able to form colonies in soft agar and show protection towards apoptosis upon serum starvation or DNA damage compared to cells transformed by the combination of Myc, cyclin D1 or SV40 large T-antigen and Ha-ras. Lines that were established after cyclin E/Ha-ras or cyclin D1/Ha-ras transformation contain a large percentage of polyploid cells. This was not observed in cells transformed with other oncoproteins and Ha-ras pointing to an involvement of D- and E type cyclins in genomic instability. The cyclin dependent kinase inhibitors p21 and p27 but also p16 completely abrogate focus formation by cyclin E and Ha-ras suggesting that the oncogenic activity of cyclin E still requires functional G1 specific cyclin/CDK complexes. Moreover, inhibition of Myc function also blocks the oncogenic activity of cyclin E indicating a requirement of Myc for cyclin E function. The findings presented here demonstrate that cyclin E can act as an oncoprotein with a potential involvement in genomic instability and the prevention of cell death. Our data also present more evidence for a strict functional interdependency between G1 cyclin/CDK complexes and c-Myc.

Animals↗
PubMed1997

Ultrasound permeabilizes CHO cells for the endonucleases AluI and benzon nuclease.

Ultrasound permeabilizes Chinese hamster ovary (CHO) cells for the endonucleases AluI and benzon nuclease which leads to the induction of chromosomal aberrations by these enzymes. A few aberrant cells were observed when trypsinized cells or adherent cells were exposed to the enzymes in the absence of ultrasound. Our data show that sonication can be used to introduce endonucleases into CHO cells. We further demonstrate that few cells can internalize endonucleases without previous permeabilization.

Animals↗
PubMed1997

Frequencies of polycentric chromosomes following combinational treatments of Chinese hamster ovary cells with restriction endonucleases and X-rays, bleomycin or DNase I.

Chinese hamster ovary cells were treated with combinations of the restriction endonucleases AluI, EcoRI or PstI and bleomycin, DNase I or X-rays. With few exceptions the frequencies of polycentric chromosomes calculated as dicentric chromosomes (DIC) were additive or less than additive after combinational treatments when compared with the effects of treatments with the single compounds. Less than additivity was found when the frequencies of DIC were higher than 150 DIC per 100 cells indicating a saturation effect. The data suggest that DNA double-strand breaks (DSB) with different end-structures produce polycentric chromosomes to the same extent as DSB with the same end-structures.

Animals↗
PubMed1997

Chromosomal aberrations in blood lymphocytes of astronauts after long-term space flights.

PURPOSE: To analyse lymphocyte chromosomes from astronauts of MIR and EUROMIR missions. MATERIALS AND METHODS: Peripheral lymphocytes from seven astronauts before and after space flights were cultured and analysed for structural chromosomal aberrations. RESULTS: Chromosome-type but not chromatid-type aberrations were significantly elevated after space flights when compared to pre-flight values. In one astronaut two rogue cells were found. CONCLUSIONS: Overall the frequencies of aberrations were found to be correlated with estimated absorbed cosmic radiation doses.

Astronauts↗