130,450 research outputs found
The Ultrasound Detection of Chromosomal Anomalies Vs Maternal Age and Serum Screening – six year survey
No full textBenefit of serum screening, maternal age and ultrasound scans in amniocentesis-a six year survey
No full text17-alpha-ethinylestradiol and norgestrel in combination induce micronucleus increases and aneuploidy in human lymphocyte and fibroblast cultures
No full textOral contraceptives are highly efficient and easily administered drugs; however, it
must not be forgotten that they are composed of chemical substances which can be
classified as potential carcinogens. Testing of a substance for genotoxicity represents
a reliable approach both to evaluate the genetic hazard and to obtain information on
its possible tumorigenic (cancerogenic) properties. The present study was undertaken
to evaluate through carefully planned and controlled investigations the in vitro cytogenetic
effects of oral contraceptives (ethynilestradiol and norgestrel mixed in the
proportion 1:5) using three different concentrations, with two different durations of
treatment (48 and 72 h), on two types of human cells (lymphocytes and fibroblasts)
and a series of short-term test procedures: sister chromatid exchange (SCE), micronucleus
test (MN), and chromosome aberrations (CA). In addition, the FISH procedure
and in vitro anaphase and metaphase preparation analyses were performed. In
contrast to CA and SCE frequencies, the frequency of MN in treated blood lymphocytes
showed higher values by comparison with the controls, although the difference
was statistically significant only for the lowest concentration (P = 0.016). When using
pancentromeric alphoid probes, the FISH procedure gave positive signals in more
than 85% of micronuclei, clearly indicating that MN may contain whole chromosomes
rather than acentric fragments. Unlike the lymphocytes, the fibroblasts showed
dose-dependent effects, although those treated with the highest hormone concentrations
showed an increased number of highly damaged cells (cytoplasmatic vacuolization,
nuclear fragmentation, etc.), a decreased number of anaphase cells, a large number
of which were abnormal, and a reduction of mitotic index. In conclusion, our data
confirm that hormones do not induce structural chromosome aberrations in lymphocytes
and indicate that ethynilestradiol and norgestrel have an aneugenic effect on fibroblast and lymphocyte cultures; FISH analysis on micronuclei from lymphocyte
cultures and anaphase preparations from fibroblast cultures support this hypothesis
SCE frequency measurement could be useful in the prenatal diagnosis of Roberts syndrome
No full textIn a previously published article (Resta et al., 2006) on Robert's syndrome in prenatal diagnosis, a case of a 36-year-old woman and her 36-year-old, nonconsanguineous husband were presented. Our findings suggest the existence of nonsense mediated decay (NMD) variability which could account for the varying severity reported in carriers of identical mutations. Furthermore, fetal cells were used to evaluate the influence of premature centromere separation (PCS) on the sister chromatid exchange (SCE) and micronucleus (MN) frequency. Given the similar variation observed in the SCE frequencies, dependent on tissue/cell type (amniotic fluid sample, chorionic villus sampling) and duration of in vitro cultures (48 hours or 72 hours), the idea was that this new piece of information could be interesting. It seems that the SCE frequency increased proportionally to the cell cycle increasing (1 degrees < 2 degrees < 3 degrees ... n). Obviously, our observations are too scarce to draw conclusions, but further investigation could be useful to corroborate or dispute these results, considering that the two techniques, (MN and SCE), are simple to perform and do not require expensive laboratory equipment
The influence of some detoxification enzyme polymorphisms on cytogenetic biomarkers and its possible repercussion on gentoxic and cancerogenic process
No full textInfluence of some detoxification enzyme polymorphisms on cytogenetic biomarkers and its possible repercussion on genotoxic and cancerogeic process
No full textMeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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