1,721,103 research outputs found
Is delayed childbearing changing gene frequencies in Western populations?
No full textAbstract
Experimental data and clinical observations suggest that delaying childbearing influences the biology of the mother-fetus relationship, with a negative effect on fetal development and predisposition to severe diseases such as type 1 diabetes. We reason that advanced maternal age may influence intrauterine selection, favoring genotypes that are more adapted to the intrauterine environment of less young women. In the present study we have investigated the relationship of maternal age to HP genotype and PGM1-Rh area (chromosome 1) that have been previously found to be associated with fertility and developmental parameters. HP phenotype was determined in 679 consecutive puerperae from the population of central Italy. PGM1 phenotype and Rh C phenotype were determined in 222 puerperae and 200 newborns. The HP 1,1 phenotype decreases and the HP 2,2 phenotype increases with maternal age. The proportion of phenotypes carrying both the Rh C and PGM1*1 alleles is much higher in puerperae older than 36 years than in puerperae of age 22 years. The frequency of the PGM1*1-Rh C haplotype increases and the frequency of the PGM1*2-Rh C haplotype decreases with maternal age. The changes in these genetic systems with advancing maternal age are similar in mothers and newborns. The delay of childbearing age, associated in Western countries with the fertility transition in addition to detrimental effects on intrauterine development and increased susceptibility to severe disorders, could bring about changes in the genetic composition of a population
Haptoglobin phenotype and reproductive success in repeated spontaneous abortion
No full textObjective: To study the reproductive success of couples with a history of repeated spontaneous abortion (RSA) with respect to the haptoglobin (Hp) phenotypes of both the wife and husband. Study design: This study examined maternal and paternal Hp in 194 couples with primary and secondary RSA recruited from the Center for Reproductive Disorders of the Institute of Obstetrics and Gynaecology at the University of Rome, La Sapienza. Reproductive success was indicated by the presence of at least one live-born infant after more than 5 years of follow-up. Results: The proportion of wives carrying Hp2/1 phenotype and with at least one live-born infant is significantly lower than that of wives without a live-born infant. Moreover, the proportion of couples in which both wife and husband possess the Hp2/1 phenotype is much lower in those with at least a live-born infant than in those without a live-born infant. Both maternal and paternal Hp contribute to reproductive success. However, the contribution of maternal Hp appears stronger than that of paternal Hp. Conclusions: Hp may play an important role in implantation and/or embryo survival. Couples in which both partners carry the Hp2/1 phenotype have a low probability of producing a live-born infant. © 2009
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Association of p53 codon 72 polymorphism with endometriosis
No full textObjective: To study the association of endometriosis with p53 codon 72 polymorphism in the population of central Italy and to search for possible interaction with the PTPN22 polymorphism. Design: Study of p53 and PTPN22 polymorphisms in women with endometriosis. Analysis of PTPN22 genotype distribution in relation to p53 genotypes. Setting: Department of Obstetrics and Gynecology of the University of Rome "Tor Vergata." Patient(S): The study included 129 women with endometriosis and 147 controls from the Caucasian population of central Italy. Intervention(S): None. Main Outcome Measure(s): Evaluation of risk for endometriosis. Result(s): No significant difference in the distribution of p53 codon 72 genotypes was observed between endometriosis patients and controls. An interaction between p53 and PTPN22 was observed: a protective action by the Arg/Arg genotype against endometriosis seems to be present only in carriers of the *T allele of PTPN22. Conclusion(s): The negative association between the Arg/Arg genotype of p53 codon 72 found in Chinese people has not been observed in Japanese and Italian populations. Interaction with genes showing different allele frequencies among ethnic groups could be responsible for the differences reported among human populations concerning the relationship between p53 and susceptibility to endometriosis
Further Observations on Associations Between the ADA Gene and Past Malaria Morbidity in Sardinia.
No full textObjectives: Adenosine Deaminase (ADA) contributes to the regulation of adenosine concentration and in turn to T cell activation. Genetic variability of ADA activity may have, therefore, an important role in resistance to malaria.
Indeed, previous studies in Sardinia have shown a lower frequency of ADA1*2 allele (associated with low ADA activity)
in areas, where malaria was heavily endemic compared to areas where malaria was not endemic. We have now studied
the ADA2 locus, another polymorphic site with two alleles ADA2 *1 and ADA2 *2 within the ADA gene.
Methods: In the area of Oristano (where malaria was endemic in the past) 51 consecutive newborns and in the area
of Nuoro (where malaria was not as endemic) 48 consecutive newborns were examined.
ADA1 and ADA2 genotypes were determined by DNA analysis.
Results: The low frequency of the ADA1*2 allele in the area where malaria was endemic is confirmed. The frequency
of the ADA2*2 allele is higher in Oristano than in Nuoro resulting in a higher frequency of the ADA1*1/ADA2*2 haplotype
in Oristano as compared to Nuoro. This suggests a selective advantage of this haplotype in a malarial
environment.
Conclusions: The ADA gene shows other polymorphic sites further studies on their role in human adaptation to
malaria could be rewarding
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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