1,791,159 research outputs found
Luteinisoiva hormoni (LH) naudan kiimakierrossa : LH ja ennenaikainen luteolyysi
No full textLuteinisoiva hormoni (LH) on aivolisäkkeen etulohkon tuottama glykoproteiini, jonka pääasialliset vaikutukset kohdistuvat munasarjoihin. LH on keskeinen hormoni ovulaatiossa, se tukee keltarauhasta diestruksen aikana ja stimuloi follikkelien thecasoluja tuottamaan androgeeneja. Hypotalamuksen tuottama gonadotropiineja vapauttava hormoni (GnRH) stimuloi aivolisäkettä tuottamaan follikkelia stimuloivaa hormonia (FSH) ja LH:ta, jotka puolestaan vaikuttavat munasarjoihin. Munasarjojen tuottamat steroidihormonit vaikuttavat palautejärjestelmän kautta hypotalamukseen ja aivolisäkkeeseen. LH:n eritys tapahtuu pulssittaisesti koko kiimakierron ajan. Keskiluteaalivaiheessa pulssien amplitudi on suurin ja frekvenssi pienin. Estrusta lähestyttäessä pulssien frekvenssi tihenee ja amplitudi pienenee, kunnes LH-pitoisuuden voimakas nousu, LH-piikki, aikaansaa ovulaation.
Tutkimuksen tarkoituksena oli selvittää, eroaako prostaglandiini- (PG) ja GnRH-käsittelyllä indusoitua ovulaatiota ja näin aikaansaatua lyhyttä kiimakiertoa edeltävä LH-eritys, LH-aalto, normaalia kiimakiertoa edeltävästä LH-erityksestä. Normaali kiimakierto esiintyi kontrolliryhmän hiehojen lisäksi osalla PG- ja GnRH-käsittelyn saaneista eläimistä. Tutkimukseen osallistui 15 tervettä, kiimakierroltaan normaalia 12 – 20 kuukauden ikäistä ayrshire-hiehoa. Kokeessa oli kaksi koeryhmää (D7 ja D14) ja yksi kontrolliryhmä (C), joissa kussakin oli kuusi eläintä. Koeryhmien hiehoille annettiin dekskloprostenolia (PG) päivänä 7 tai 14. Kaksikymmentäneljä tuntia PG-injektion jälkeen kullekin koeryhmän eläimelle annettiin GnRH-injektio ovulaation indusoimiseksi. Kontrolliryhmän hiehojen, joista osa oli samoja kuin ryhmässä D7, kiimat synkronointiin hormonikierukan avulla ja niiden annettiin ovuloida vapaasti.
Koe-eläinten munasarjoja tutkittiin ultraäänilaitteella kokeen aikana ja eläimistä kerättiin verinäytteitä progesteroni- ja LH-pitoisuuksien määrittämistä varten. Plasman LH-pitoisuus mitattiin puolen tunnin välein otetuista näytteistä, koeryhmissä alkaen GnRH-injektiosta kuuden tunnin ajan ja kontrolliryhmässä alkaen 36 tuntia kierukan poistosta jatkuen 31 tunnin ajan.
Lyhyitä kiimakiertoja esiintyi ryhmässä D7 6/6 kpl ja ryhmässä D14 2/5 kpl, mutta kontrolliryhmässä niitä ei havaittu ainoatakaan. Ero koeryhmien ja kontrolliryhmän välillä oli tilastollisesti merkitsevä. Niiden hiehojen, joiden kiimakierto oli lyhyt, progesteronieritys poikkesi selvästi normaalin kiimakierron omaavien eläinten erityksestä. LH-aalloista tutkittiin erikseen LH:n maksimiarvo, aallon kestoaika, aika ensimmäisestä merkitsevästä noususta maksimiarvoon ja ovulaatioon, aika maksimiarvosta ovulaatioon sekä totaalieritystä kuvaava käyrän alapuolinen pinta-ala (AUC). Koeryhmien välillä ei todettu olevan eroa LH-erityksessä riippumatta siitä, onko seuraava kiimakierto lyhyt vai normaali. Koeryhmien LH-aalto erosi kuitenkin niin paljon kontrolliryhmän aallosta, että ei ole poissuljettua, että tällä voisi olla vaikutusta tulevaan kiimakiertoon
LH-PCR, Ecoplate, CO2 and Dung mass loss data
No full textLH-PCR, Ecoplate, CO2 and Dung mass loss dat
Microvesicle-mediated release of soluble LH/hCG receptor (LHCGR) from transfected cells and placenta explants
No full textPlacental hCG and pitutary LH transduce signals in target tissues through a common receptor (LHCGR). We
demonstrate that recombinant LHCGR proteins which include the hormone-binding domain are secreted from
transfected cells and that natural LHCGR is also secreted from human placental explants. LHCGR recombinant
proteins representing varying lengths of the N-terminal extracellular domain were expressed in Chinese Hamster
Ovary cells in suspension culture. Secretion was minimal up to 72h but by 96h 24-37% of the LHCGR had been
released into the culture medium. The secreted proteins were folded and sensitive to glycosidases suggesting
N-linked glycosylation. Secretion was independent of recombinant size and was mediated via structurally defined
membrane vesicles (50-150nm). Similarly cultured human early pregnancy placental explants also released LHCGR
via microvesicles. These studies provide the first experimental evidence of the possible mechanistic basis of the
secretion of LHCGR
Differential expression and functional characterization of luteinizing hormone receptor splice variants in human luteal cells : Implications for luteolysis
No full textThe human LH receptor (LHR) plays a key role in luteal function and the establishment of pregnancy through its interaction with the gonadotropins LH and human chorionic gonadotropin. We previously identified four splice variants of the LHR in human luteinized granulosa cells (LGCs) and corpora lutea (CL). Real-time quantitative PCR revealed that expression of the full-length LHR (LHRa) and the most truncated form (LHRd) changed significantly in CL harvested at different stages of the ovarian cycle (P < 0.01, ANOVA). LHRa expression was reduced in the late luteal CL (P<0.05). Conversely, an increase in LHRd expression was observed in the late luteal CL (P<0.01). Chronic manipulation of human chorionic gonadotropin in LGC primary cultures supported the in vivo findings. LHRd encodes a protein lacking the transmembrane and carboxyl terminal domains. COS-7 cells expressing LHRd were unable to produce cAMP in response to LH stimulation. COS-7 cells coexpressing LHRd and LHRa also failed to generate cAMP in response to LH, suggesting that this truncated form has a negative effect on the signaling of LHRa. Immunofluorescence staining ofLGC and COS-7 cells implied that there is a reduction in cell surface expression ofLHRa when LHRd is present. Overall, these results imply expression of LHR splice variants is regulated in the human CL. Furthermore, during functional luteolysis a truncated variant could modulate the cell surface expression and activity of full-length LHR.Peer reviewe
Proline-rich tyrosine kinase 2 mediates gonadotropin-releasing hormone signaling to a specific extracellularly regulated kinase-sensitive transcriptional locus in the luteinizing hormone beta-subunit gene
No full textG protein-coupled receptor regulation of gene transcription primarily occurs through the phosphorylation of transcription factors by MAPKs. This requires transduction of an activating signal via scaffold proteins that can ultimately determine the outcome by binding signaling kinases and adapter proteins with effects on the target transcription factor and locus of activation. By investigating these mechanisms, we have elucidated how pituitary gonadotrope cells decode an input GnRH signal into coherent transcriptional output from the LH beta-subunit gene promoter. We show that GnRH activates c-Src and multiple members of the MAPK family, c-Jun NH2-terminal kinase 1/2, p38MAPK, and ERK1/2. Using dominant-negative point mutations and chemical inhibitors, we identified that calcium-dependent proline-rich tyrosine kinase 2 specifically acts as a scaffold for a focal adhesion/cytoskeleton-dependent complex comprised of c-Src, Grb2, and mSos that translocates an ERK-activating signal to the nucleus. The locus of action of ERK was specifically mapped to early growth response-1 (Egr-1) DNA binding sites within the LH beta-subunit gene proximal promoter, which was also activated by p38MAPK, but not c-Jun NH2-terminal kinase 1/2. Egr-1 was confirmed as the transcription factor target of ERK and p38MAPK by blockade of protein expression, transcriptional activity, and DNA binding. We have identified a novel GnRH-activated proline-rich tyrosine kinase 2-dependent ERK-mediated signal transduction pathway that specifically regulates Egr-1 activation of the LH beta-subunit proximal gene promoter, and thus provide insight into the molecular mechanisms required for differential regulation of gonadotropin gene expression
Effect of LH-RH Cholesterol Pellet on Ovarian Maturation in Ayu, Plecoglossus altivelis
No full textLH-RH cholesterol pellet formulated for a long delivery was administered to female Ayu, Plecoglossus altivelis which were maintained at ovarian maturation-suppressive condition of the long photoperiod (15L: 9D). Two types of hormone such as native LH-RH and des-Gly¹⁰ [D-Ala⁶]-LH-RH ethylamide (LH-RH ethylamide) were used in this study. In experiment I (native LH-RH), the initial control fish with an early phase of yolky oocytes showed an atrophy of ovary at the end of experiment, whereas the fish treated with LH-RH at a level of 100 µg showed acceleration of ovarian maturation and ovulation in some fish. All the fish received LH-RH 200 µg overcame against the ovarian maturation-suppressive condition and ovulated within 32 days. In experiment II (LH-RH ethylamide), the initial control fish with non-yolky oocyte showed a slight increase of GSI, whereas the fish treated with LH-RH ethylamide at a level of 50 or 100 µg ovulated within 53 days. Furthermore, LH-RH ethylamide was more potent in inducing maturation and ovulation of Ayu than native LH-RH. Consequently, LH-RH cholesterol pellet was demonstrated a longly active effect for yolk formation, final maturation and ovulation of fish held under the ovarian maturation-suppressive condition.departmental bulletin pape
Writing a History of Women's Writing from 700 to 1500
No full textHow can a history of British women’s writing be written? Such a project must necessarily be collaborative if it is to attempt to be comprehensive, but even then any claim to comprehensiveness has to be qualified: paradoxically the more expansive the history, the more partial it will be. The challenges of writing such a history are perhaps even greater for scholars working in the early periods because we are forced to confront and to rethink many deeply ingrained assumptions about women’s writing. This introductory essay focuses on a period of literary history that is often marginalized in accounts of women’s writing in English: the Middle Ages. It is a widely accepted view that there are only two women writers in English in the period before 1500, and therefore there is little to be said for an age (or ages) when women writers were so much an exception. Furthermore, the two medieval English women writers whose names are widely known, Julian of Norwich (1342/3-after 1416) and Margery Kempe (c.1373-after 1439), did not think of themselves as writers or authors. Nor were they responsible for literature as it is thought of today—they did not compose poetry, or romances, or fiction of any sort. Even these two ‘named’ women writers do not comfortably fit established evolutionary models of women’s literary history over the longue durée, with their emphases on the spread of literacy, the bias towards print culture, and the emergence of the woman poet, and ultimately of the professional author of drama or fiction. Yet the difficulty of locating how the medieval period fits in to literary history is not unique to women’s writing: medieval understandings of authorship, literature, and national identity, and the contexts and processes of writing and textual circulation were quite distinct from later periods and therefore deemed problematic more generally. This essay explores some of these issues and reflects on the difficulties we face writing a history of early women's writing
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
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