6,372 research outputs found
Microvesicle-mediated release of soluble LH/hCG receptor (LHCGR) from transfected cells and placenta explants
Full text linkPlacental 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
Ar-40-Ar-39 thermo chronological constraints on the exhumation of ultrahigh-pressure metamorphic rocks in the Sulu terrane of eastern China
No full textBlowout of non-premixed turbulent jet flames with coflow under microgravity condition
No full textThe blowout behavior of non-premixed turbulent coflow jet flames under microgravity environment was studied experimentally by utilizing a 3.6 s drop tower. Variations of flames leading to liftoff as well as blowout were examined by varying the coflow velocity and compared with those obtained under the normal gravity condition. A modeling work was conducted to incorporate the effects of the gravity (buoyancy) and coflow velocity on blowout behavior. Major findings include: (1) the flame length in microgravity was longer than that in normal gravity and decreased with increasing coflow velocity. The flame in microgravity showed more intense yellow luminosity with larger sooting zone; (2) the flame liftoff height increased with increasing coflow velocity in both gravity levels. The flame base was closer to the burner in microgravity as compared with that in normal gravity; (3) the blowout velocity in microgravity was appreciably larger than that obtained in normal gravity; and (4) a physical model based on Damkohler number was developed by using similarity solutions to characterize the differences in the blowout limits considering both the coflow and gravity (buoyancy) effects. The proposed model can successfully predict the experimental data. This work provided new data and basic scaling analysis for blowout limit of non-premixed turbulent jet flames considering both the coflow and gravity (buoyancy) effects. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved
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
Comparisons of the LH Moments and the L Moments
Full text linkThis paper discusses comparisons of the LH moments method with L moments method. LH moments, a generalization of L moments, based on linear combinations of higher-order statistics was introduced for charactering the upper part of distributions and larger events in data by Wang (1997). Analysis of observed data shows that using LH moments estimates of the upper part of distribution events are expected to be more reasonable than the L moments estimates. A comparison of the LH moment diagram and the L moment diagram of the data also shows that the GEV distribution describes the LH moment ratios better than the L moments
Comparative proteomic analysis of two contrasting cultivars reveals the mechanism of sugar beet response to freezing stress
No full textSugar beet (Beta vulgaris L.) is an economic crop integrating grain and feed production, and is a major source of sucrose. Freezing stress can cause dehydration and necrosis of seedlings. Therefore, it is important to study the basic physiological and proteomic mechanisms of different sugar beet cultivars under freezing stress. In this study, compared with freezing-sensitive (SME) cultivar, the freezing-tolerant (TBP) cultivar showed higher photosynthetic rate, antioxidant enzyme activity, proline and abscisic acid levels, lower malondialdehyde and gibberellin levels and relative conductivity under freezing stress. Moreover, comparative proteomic analysis revealed that proteins mapped to photosynthesis, tryptophan synthesis, anthocyanin synthesis, tricarboxylic acid cycle, reactive oxygen species scavenging and sucrose metabolism pathways were more abundant in TBP, indicating that these metabolic pathways may be beneficial to improve freezing tolerance. In particular, compared with SME cultivar, proteins involved in tryptophan synthesis were found to be upregulated only in TBP cultivar under freezing stress, including phospho-2-dehydro-3-deoxyheptonate aldolase 1, probable inactive shikimate kinase like 1, and anthranilate synthase alpha subunit 2. In addition, quantitative real-time polymerase chain reaction analysis showed that mRNA expression of these three proteins was significantly upregulated in the freezing stress (-5 celcius) vs. control group in the TBP cultivar. Additionally, tryptophan content in TBP leaves increased significantly under freezing stress, while in SME it showed no significant change. Furthermore, the application of exogenous tryptophan solution significantly reduced the mortality rate of sugar beet seedlings (17day-old) under freezing stress. This study provides a foundation for further functional analysis to fully understand the molecular mechanisms of adaptation to freezing stress in sugar beet
Physiological Response of Sugar Beet Seedlings to Ferrous, Hypoxia, and Interactive Ferrous-Hypoxia Stresses
No full textCrops during their growth period can encounter waterlogging problems which often lead to an oxygen-deficient environment in the rhizosphere and rapid increases in the availability of iron in the soil. Therefore, a hydroponic experimental system was designed to evaluate the response mechanism of sugar beet to single ferrous, hypoxia stress, and interactive ferrous-hypoxia stress through physiological and biochemical analyses. In this study, stress conditions were applied in a factorial design: three ferrous treatments (0.06, 0.48, and 1.92 mmol) and three hypoxia treatments (normal, 4-day hypoxia, and 8-day hypoxia) were set against one another, totaling 9 experimental treatments. We measured morphological indexes, biomass production, root vigor, the electrolytic leakage, chlorophyll content, gas exchange, reactive oxygen species concentration, malonaldehyde concentration, antioxidant enzyme activity, proline, soluble sugar concentration, and plant nutrient contents of sugar beet seedlings under different treatments. Under single stress, the growth of seedlings was inhibited, and interactive stress enhanced this inhibition. Compared to the control, 1.92 mmol Fe and 8 days of hypoxia induced a 16% and 43% reduction in the total plant height of seedlings, respectively, while interactive ferrous-hypoxia stress produced a 51% reduction. Single and interactive stress damaged the roots of seedlings, root vigor reached its lowest under interactive stress, and Fe concentrations increased, but N, P, K, Mn, and Zn decreased. Chlorophyll content decreased under ferrous and interactive stress. At the same time, stresses affected the gas exchange of leaves, and the stomatal conductance, transpiration rate, and intrinsic water use efficiency decreased, resulting in insufficient photosynthetic capacity of the seedlings, and biomass accumulation decreased. Furthermore, the antioxidant enzyme activity and osmotic adjustment substance content of seedlings increased with an increase of the degree of stress. Among these, the POD activity of seedlings grown under 1.92 mmol Fe and hypoxia for 8 days was upregulated by 7.5 and 1.5 times compared with the control, while the interactive stress induced a 10.5 times upregulation. Under single stress, seedling growth was inhibited to varying degrees, while under interactive stress, this inhibition was enhanced. Seedlings also improved their antioxidant capacity to resist the damage caused by stress, but on the whole, stress had a profound effect on the plants
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
Full text linkG 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
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
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