1,720,955 research outputs found
The role of transmission electron microscopy analysis in different cases of reduced motility in human spermatozoa
No full textThe aim of this review is to highlight the pivotal role of transmission electron microscopy (TEM) analysis in the diagnosis of human sperm pathologies related to flagellum and affecting motility.
The analysis of sperm motility plays a central role in the evaluation of male fertility, as it is known that a high percentage of poorly motile or immotile sperm will not be able to fertilize. The study of sperm flagellum and its abnormal forms is generally carried out by light microscope with obvious technical limitations. Only the use of TEM allows for the performance of an ultrastructural evaluation of sperm flagellar assembly with a precise characterization of anomalies, also extrapolating the functional aspect. Severely reduced or completely absent sperm motility in subfertile or infertile men is associated with submicroscopic alterations in the cytoskeletal structure of sperm flagellum, in the mitochondria structure and assembly, in the axonemal pattern and periaxonemal accessory structures, such as the outer dense fibres and fibrous sheath. Sperm anomalies are classified as non-specific, or non-systematic sperm defects, or as systematic sperm defects. The first and most frequent type is related to a heterogeneous combination of randomly distributed alterations affecting the head and the tail organelles in a varied percentage in sperm ejaculate. These alterations can be related to andrological pathologies or to other endogenous or exogenous factors. Necrozoospermia, an extreme manifestation of asthenozoospermia, is, a rather rare phenomenon characterized by an increase in non-viable sperm up to the persistent presence of 100% dead spermatozoa in different ejaculates from the same patient. TEM has proved to be the only tool able to specifically characterize the morphological features of the systematic sperm defects in which an identical and specific alteration affects the vast majority of the sperm population in sterile patients. These defects tend to show family clustering and are significantly more frequent in individuals with a history of consanguinity. The most documented sperm defects of supposed genetic origin affecting the tail structures include: "Dysplasia of Fibrous Sheath", "Primary Ciliary Dyskinesia ", "Detached tail", "Absence of fibrous sheath ", "Absent axoneme"
Sperm ultrastructure and 18, X, Y aneuploidies in a man with a 46 XY, 47 XY + 18 mosaic karyotype: case report
No full textPURPOSE:
To describe sperm morphology and meiotic segregation in the case of a man with a 46 XY/ 47 XY + 18 mosaic karyotype.
MATERIALS AND METHODS:
A 25-year-old man came to our Centre for semen analysis. Morphological sperm evaluation was performed by light and electron microscopy; meiotic segregation was examined by fluorescence in situ hybridisation (FISH) technique using probes for chromosomes 18, X and Y. PCR was carried out on DNA from peripheral blood lymphocytes to analyze Y microdeletions.
RESULTS:
Mathematically elaborated transmission electron microscopy data highlighted a low number of sperm devoid of ultrastructural defects, and the presence of characteristics of apoptosis and immaturity. FISH showed the presence of aneuploidies of chromosome 18 and sex chromosomes.
CONCLUSIONS:
In this case of mosaicism morphological and meiotic spermatogenetic impairment is shown, as well as structural chromosomal alterations
TEM and FISH studies in sperm from men of couples with recurrent pregnancy loss
No full textThe role of the male partner in recurrent pregnancy loss (RPL) is not clear. In this study, semen characteristics of 22 men whose partners had experienced RPL were examined by light microscopy. Sperm morphology was analysed by transmission electron microscopy (TEM) and the data were mathematically elaborated to obtain numerical indices expressing the status of an ejaculate: the fertility index and the percentage of apoptosis, necrosis and immaturity. Sperm apoptosis and necrosis were also evaluated by annexin V/propidium iodide assay. To explore the status of meiotic segregation, fluorescence in situ hybridisation (FISH) with probes for chromosomes 18, X and Y, was applied directly on sperm nuclei. Sperm characteristics from a group of men of proven fertility were used as controls. Among the considered sperm characteristics, apoptosis (P < 0.01), 1818YY diploidy (P < 0.05) and 18YY disomy (P < 0.01) scores were significantly higher in men with RPL compared with controls. Our study showed that some patients with normal semen parameters can present a slight increase in aneuploidy compared with controls, indicating a possible involvement of sperm in some cases of RPL. Chromosomal FISH analysis and chromatin tests of sperm could be included in RPL work-ups when no other cause has been detected. © 2009 Blackwell Verlag GmbH
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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