1,721,105 research outputs found
Krüppel-like factor 4 is widely expressed in the mouse male and female reproductive tract and responds as an immediate early gene to activation of the protein kinase A in TM4 Sertoli cells
No full textKrüppel-like factor 4 (KLF4) is a zinc finger transcription factor critically involved in cell proliferation, differentiation, and carcinogenesis. Recently, KLF4 has also been used for the generation of induced pluripotent stem cells. In this study, we analyzed
Klf4
expression in different mouse tissues using northern blot analysis and immunohistochemistry. Focusing on the male and female reproductive tract, we showed for the first time that KLF4 is expressed in the epithelia of the murine uterus and the vagina. In the male reproductive tract, we detected KLF4 in the epithelia of the epididymis, ductus deferens, coagulating gland, and the penis. As KLF4 is strongly inducible by FSH signaling in Sertoli cells and as this transcription factor is also involved in Sertoli cell development, we employed the mouse Sertoli cell line TM4 as a model system to investigate i) the induction kinetics of
Klf4
upon activation of the cAMP/protein kinase A pathway by forskolin and ii) the effects of
Klf4
induction on TM4 cell cycle progression. Interestingly,
Klf4
mRNA and protein were rapidly but transiently induced, reaching peak levels after 90–120 min and declining to basal levels within 4 h. Compared with the inducible cAMP early repressor, an immediate early response gene, the induction kinetics of
Klf4
is much faster. In conclusion,
Klf4
is an immediate early gene in TM4 cells and its expression in several epithelia of the male and female reproductive tract suggests an important role of
Klf4
in mouse reproductive functions
Primordial germ cells do not migrate along nerve fibres in marmoset monkey and mouse embryos
No full textPrimordial germ cells (PGCs) are the embryonic precursors of spermatozoa and eggs. In mammals, PGCs arise early in embryonic development and migrate from their tissue of specification over a significant distance to reach their destinations, the genital ridges. However, the exact mechanism of translocation is still debated. A study on human embryos demonstrated a very close spatial association between migrating PGCs and developing peripheral nerves. Thus, it was proposed that peripheral nerves act as guiding structures for migrating PGCs. The goal of the present study is to test whether the association between nerves and PGCs may be a human-specific finding or whether this represents a general strategy to guide PGCs in mammals. Therefore, we investigated embryos of different developmental stages from the mouse and a non-human primate, the marmoset monkey (
Callithrix jacchus
), covering the phase from PGC emergence to their arrival in the gonadal ridge. Embryo sections were immunohistochemically co-stained for tubulin beta-3 chain (TUBB3) to visualise neurons and Octamer-binding protein 4 (OCT4 (POU5F1)) as marker for PGCs. The distance between PGCs and the nearest detectable neuron was measured. We discovered that in all embryos analysed of both species, the majority of PGCs (>94%) was found at a minimum distance of 50 µm to the closest neuron and, more importantly, that the PGCs had reached the gonads before any TUBB3 signal could be detected in the vicinity of the gonads. In conclusion, our data indicate that PGC migration along peripheral nerves is not a general mechanism in mammals
The involvement of gonadotropin inhibitory hormone and kisspeptin in the metabolic regulation of reproduction
No full textRecently, kisspeptin (KP) and gonadotropin inhibitory hormone (GnIH), two counteracting neuropeptides, have been acknowledged as significant regulators of reproductive function. KP stimulates reproduction while GnIH inhibits it. These two neuropeptides seem to be pivotal for the modulation of reproductive activity in response to internal and external cues. It is well-documented that the current metabolic status of the body is closely linked to its reproductive output. However, how reproductive function is regulated by the body's energy status is less clear. Recent studies have suggested an active participation of hypothalamic KP and GnIH in the modulation of reproductive function according to available metabolic cues. Expression of
KISS1
, the KP encoding gene, is decreased while expression of
RFRP
(
NPVF
), the gene encoding GnIH, is increased in metabolic deficiency conditions. The lower levels of KP, as suggested by a decrease in
KISS1
gene mRNA expression, during metabolic deficiency can be corrected by administration of exogenous KP, which leads to an increase in reproductive hormone levels. Likewise, administration of RF9, a GnIH receptor antagonist, can reverse the inhibitory effect of fasting on testosterone in monkeys. Together, it is likely that the integrated function of both these hypothalamic neuropeptides works as a reproductive output regulator in response to a change in metabolic status. In this review, we have summarized literature from nonprimate and primate studies that demonstrate the involvement of KP and GnIH in the metabolic regulation of reproduction
Misleading and reliable markers to differentiate between primate testis-derived multipotent stromal cells and spermatogonia in culture
No full textParameters assessing neurological status in malignant glioma patients: prognostic value for survival and relapse-free time
No full textMalignant gliomas are the commonest primary brain tumours in adults and harbour a dismal prognosis. So far, established parameters with predictive significance for prognosis do not include the neurological functional assessment of patients. The aim of this study was to investigate the prognostic value of parameters assessing neurological status in malignant glioma patients for outcome and survival. Evaluation of neurological status included the Sawaya Functional Grade (SFG) and the Neurological Performance Scale (NPS). Moreover, the Karnofsky Performance Status (KPS), medical risk factors, extension of resection, postoperative complications, and the predictive value of these variables for outcome and survival were studied. For this purpose, we have analysed 110 consecutive patients with malignant gliomas who were treated at our institution. As expected, age (p < 0.001), KPS (p=0.003) and extent of resection (p 0.001) were good predictors of survival. Strikingly, SFG and NPS showed the highest significant correlation with survival (both p < 0.0001) and, furthermore, they were the only predictors of the relapse-free time (p=0.035 and p=0.004, respectively). Our data strongly suggests that SFG and NPS accurately predict both survival and relapse-free time, which may add a valuable tool for tailoring individual therapy strategies
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
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