1,721,032 research outputs found
Hypothesis: Irisin is a metabolic trigger for the activation of the neurohormonal axis governing puberty onset
No full texthttps://doi.org/10.13039/501100004938 DP
Kisspeptin signalling in the physiology and pathophysiology of the urogenital system
No full textKisspeptin is a peptide hormone, which signals via the G-protein-coupled kisspeptin receptor (KISS1R). Kisspeptin-KISS1R signalling has been implicated in various physiological and pathophysiological processes in the urogenital system, including critical roles in ovarian function as a key player in the regulation of oocyte development. Kisspeptin also has roles in several different functions of the male reproductive tract, such as spermatogenesis and sperm capacitation, and is also thought to be involved in kidney physiology-studies in preclinical animal models have reported that expression of kisspeptin and/or KISS1R is altered in chronically impaired kidneys. The wider importance of kisspeptin action in the urogenital tract has been highlighted by the finding that it suppresses metastasis of urogenital carcinomas; besides the possible therapeutic potential of this finding, tissue and tumour-stage-specific alterations in kisspeptin and KISS1/KISS1R expression could potentially be used as biomarkers for the diagnosis and prognosis of urogenital carcinomas
Metabolic Impact on the Hypothalamic Kisspeptin-Kiss1r Signaling Pathway
No full textA large body of data has established the hypothalamic kisspeptin (KP) and its receptor, KISS1R, as major players in the activation of the neuroendocrine reproductive axis at the time of puberty and maintenance of reproductive capacity in the adult. Due to its strategic location, this ligand-receptor pair acts as an integrator of cues from gonadal steroids as well as of circadian and seasonal variation-related information on the reproductive axis. Besides these cues, the activity of the hypothalamic KP signaling is very sensitive to the current metabolic status of the body. In conditions of energy imbalance, either positive or negative, a number of alterations in the hypothalamic KP signaling pathway have been documented in different mammalian models including nonhuman primates and human. Deficiency of metabolic fuels during fasting causes a marked reduction of Kiss1 gene transcript levels in the hypothalamus and, hence, decreases the output of KP-containing neurons. Food intake or exogenous supply of metabolic cues, such as leptin, reverses metabolic insufficiency-related changes in the hypothalamic KP signaling. Likewise, alterations in Kiss1 expression have also been reported in other situations of energy imbalance like diabetes and obesity. Information related to the body’s current metabolic status reaches to KP neurons both directly as well as indirectly via a complex network of other neurons. In this review article, we have provided an updated summary of the available literature on the regulation of the hypothalamic KP-Kiss1r signaling by metabolic cues. In particular, the potential mechanisms of metabolic impact on the hypothalamic KP-Kiss1r signaling, in light of available evidence, are discussed
Irisin in the primate hypothalamus and its effect on GnRH in vitro
No full textIrisin, encoded by the
FNDC5
gene, is a recently discovered endocrine factor mainly secreted as a myokine and adipokine. However, irisin/
FNDC5
expression has also been reported in different other organs including components of the reproductive axis. Yet, there is the scarcity of data on
FNDC5
/irisin expression, regulation and its reproductive effects, particularly in primates. Here, we report the expression of
FNDC5
/irisin, along with
PGC1A
(peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and
ERRA
(estrogen-related receptor alpha), in components of the reproductive axis of marmoset monkeys. Hypothalamic
FNDC5
and
ERRA
transcript levels are developmentally regulated in both male and female. We further uncovered sex-specific differences in
FNDC5
,
ERRA
and
PGC1A
expression in muscle and the reproductive axis. Moreover, irisin and ERRα co-localize in the marmoset hypothalamus. Additionally, in the arcuate nucleus of rhesus monkeys, the number of irisin+ cells was significantly increased in short-term fasted monkeys as compared to
ad libitum
-fed monkeys. More importantly, we observed putative interaction of irisin-immunoreactive fibers and few GnRH
-
immunoreactive cell bodies in the mediobasal hypothalamus of the rhesus monkeys. Functionally, we noted a stimulatory effect of irisin on GnRH synthesis and release in mouse hypothalamic neuronal GT1-7 cells. In summary, our findings show that
FNDC5
and irisin are developmentally, metabolic-status dependently and sex-specifically expressed in the primate hypothalamic–pituitary–gonadal axis and exert a stimulatory effect on GnRH expression and release in mouse hypothalamic cells. Further studies are required to confirm the reproductive effects of irisin
in vivo
and to illuminate the mechanisms of its regulation
Expression and actions of GnIH and its orthologs in vertebrates: Current status and advanced knowledge
No full textQuaid-i-Azam University Research FundHigher Education Commission of PakistanNational Natural Science Foundation 50110000180
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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