3,429 research outputs found
Detection and toxicity evaluation of pyrrolizidine alkaloids in medicinal plants Gynura bicolor and Gynura divaricata collected from different Chinese locations
Two edible plants in Southeast Asia, Gynura bicolor and G.divaricata, are not only known to be nutritive but also useful as medicinal herbs. Previous phytochemical investigation of Gynura species showed the presence of hepatotoxic pyrrolizidine alkaloids (PAs), indicating the toxic risk of using these two plants. The present study was designed to analyze the distribution of PA components and tried to evaluate the preliminary toxicity of these two Gynura species. Eight samples of G.bicolor and G.divaricata from five different Chinese locations were collected and their specific PAs were qualitatively characterized by applying an UPLC/MS/MS spectrometry method. Using a pre-column derivatization HPLC method, the total retronecine ester-type PAs in their alkaloids extracts were quantitatively estimated as well. Finally, their genotoxicity was investigated with an effective high-throughput screening method referred to as Vitotox test and their potential cytotoxicity was tested on HepG2 cells. It was found that different types of PAs were widely present in Gynura species collected from south of China. Among them, no significant genotoxic effects were detected with serial concentrations through the present invitro assay. However, the cytotoxicity assay of Gynura plants collected from Jiangsu displayed weak activity at the concentration of 100mg/ml. It is important to note that this research validates in part the indication that the use of Gynura species requires caution
When Social Influence Meets Item Inference
Research issues and data mining techniques for product recommendation and
viral marketing have been widely studied. Existing works on seed selection in
social networks do not take into account the effect of product recommendations
in e-commerce stores. In this paper, we investigate the seed selection problem
for viral marketing that considers both effects of social influence and item
inference (for product recommendation). We develop a new model, Social Item
Graph (SIG), that captures both effects in form of hyperedges. Accordingly, we
formulate a seed selection problem, called Social Item Maximization Problem
(SIMP), and prove the hardness of SIMP. We design an efficient algorithm with
performance guarantee, called Hyperedge-Aware Greedy (HAG), for SIMP and
develop a new index structure, called SIG-index, to accelerate the computation
of diffusion process in HAG. Moreover, to construct realistic SIG models for
SIMP, we develop a statistical inference based framework to learn the weights
of hyperedges from data. Finally, we perform a comprehensive evaluation on our
proposals with various baselines. Experimental result validates our ideas and
demonstrates the effectiveness and efficiency of the proposed model and
algorithms over baselines.Comment: 12 page
Nouvelles données sur l'anatomie du lophophore chez des linguloïdes du Cambrien inférieur duLagerstätte de Chengjiang, Sud-Ouest de la Chine
Une succession de types de lophophore est décrite chez des brachiopodes linguloïdes dans les dépôts du Chengjiang (Cambrien inférieur) au Sud de la Chine. Ces types vont depuis un lophophore trocholophe, au schizolophe et au spirolophe à enroulement spiral simple. Cette succession d'âge Atdabanien existe encore dans le développement du lophophore chez les linguloïdes actuels, ce qui démontre une similarité entre les lophophores au Cambrien et dans l'Actuel. Des dispositions aberrantes des bras lophophoraux qui tendent à s'étendre de façon inhabituelle dans et hors de la coquille sont illustrées dans une dizaine d'exemplaires.A succession of developmental types in the lophophores of lingulid brachiopods is reported from the Early Cambrian Chengjiang deposits of South China. These types range from trocholophe, schizolophe to simple coiled spirolophe. Of Atdabanian age, this succession of forms is mirrored in the ontogeny of the lophophore of Recent linguloids, thus demonstrating a close similarity in the development of the lophophores of Cambrian and Recent forms. We illustrate also more than 10 extraordinary specimens with aberrant dispositions of the lophophoral arms that extend to unusual lengths either inside or outside the shell
Germline Stem Cell Gene PIWIL2 Mediates DNA Repair through Relaxation of Chromatin
DNA damage response (DDR) is an intrinsic barrier of cell to tumorigenesis initiated by genotoxic agents. However, the mechanisms underlying the DDR are not completely understood despite of extensive investigation. Recently, we have reported that ectopic expression of germline stem cell gene PIWIL2 is associated with tumor stem cell development, although the underlying mechanisms are largely unknown. Here we show that PIWIL2 is required for the repair of DNA-damage induced by various types of genotoxic agents. Upon ultraviolet (UV) irradiation, silenced PIWIL2 gene in normal human fibroblasts was transiently activated after treatment with UV light. This activation was associated with DNA repair, because Piwil2-deficienct mouse embryonic fibroblasts (mili-/- MEFs) were defective in cyclobutane pyrimidine dimers (CPD) repair after UV treatment. As a result, the UV-treated mili-/- MEFs were more susceptible to apoptosis, as characterized by increased levels of DNA damage-associated apoptotic proteins, such as active caspase-3, cleaved Poly (ADP-ribose) polymerase (PARP) and Bik. The impaired DNA repair in the mili-/- MEFs was associated with the reductions of histone H3 acetylation and chromatin relaxation, although the DDR pathway downstream chromatin relaxation appeared not to be directly affected by Piwil2. Moreover, guanine–guanine (Pt-[GG]) and double strand break (DSB) repair were also defective in the mili-/- MEFs treated by genotoxic chemicals Cisplatin and ionizing radiation (IR), respectively. The results indicate that Piwil2 can mediate DNA repair through an axis of Piwil2 → histone acetylation → chromatin relaxation upstream DDR pathways. The findings reveal a new role for Piwil2 in DNA repair and suggest that Piwil2 may act as a gatekeeper against DNA damage-mediated tumorigenesis
Antibody dependent enhancement infection of Enterovirus 71 in vitro and in vivo
BACKGROUND: Human enterovirus 71 (EV71) has emerged as a significant cause of acute encephalitis and deaths in young children. The clinical manifestations caused by EV71 varied from mild hand, foot and mouth disease to severe neurological complications and deaths, but its pathogenesis remains elusive. Antibody dependent enhancement (ADE) infection has been reported in various viruses and has been shown to contribute to disease severity. RESULTS: In this study, the presence of sub-neutralizing antibody was demonstrated to enhance EV71 infection in THP-1 cells and increase the mortality of EV71 infection in a suckling mouse model. Further, a secondary infection model was established to characterize the correlation between ADE and disease severity, and primary asymptomatic EV71 infection was shown to increase the mortality of the secondary EV71 infection in suckling mice. CONCLUSIONS: Together, these in vitro and in vivo experiments strongly supported the hypothesis of ADE infection of EV71. The present findings indicate ADE might contribute to the pathogenesis of severe EV71 infection, and raise practical issues of vaccine development and antibody-based therapy
Fast radio bursts generated by coherent curvature radiation from compressed bunches for FRB 20190520B
The radiation mechanism of fast radio bursts (FRBs) has been extensively
studied but still remains elusive. Coherent radiation is identified as a
crucial component in the FRB mechanism, with charged bunches also playing a
significant role under specific circumstances. In the present research, we
propose a phenomenological model that draws upon the coherent curvature
radiation framework and the magnetized neutron star, taking into account the
kinetic energy losses of outflow particles due to inverse Compton scattering
(ICS) induced by soft photons within the magnetosphere. By integrating the ICS
deceleration mechanism for particles, we hypothesize a potential compression
effect on the particle number density within a magnetic tube/family, which
could facilitate achieving the necessary size for coherent radiation in the
radial direction. This mechanism might potentially enable the dynamic formation
of bunches capable of emitting coherent curvature radiation along the curved
magnetic field. Moreover, we examine the formation of bunches from an energy
perspective. Our discussion suggests that within the given parameter space the
formation of bunches is feasible. Finally, we apply this model to FRB
20190520B, one of the most active repeating FRBs discovered and monitored by
FAST. Several observed phenomena are explained, including basic
characteristics, frequency downward drifting, and bright spots within certain
dynamic spectral ranges.Comment: 16 pages, 9 figures, and 1 table. Accepted for publication in Ap
Using microlensed quasars to probe the structure of the Milky Way
This paper presents an investigation into the gravitational microlensing of
quasars by stars and stellar remnants in the Milky Way. We present predictions
for the all-sky microlensing optical depth, time-scale distributions and event
rates for future large-area sky surveys. As expected, the total event rate
increases rapidly with increasing magnitude limit, reflecting the fact that the
number density of quasars is a steep function of magnitude. Surveys such as
Pan-STARRS and LSST should be able to detect more than ten events per year,
with typical event durations of around one month. Since microlensing of quasar
sources suffers from fewer degeneracies than lensing of Milky Way sources, they
could be used as a powerful tool for recovering the mass of the lensing object
in a robust, often model-independent, manner. As a consequence, for a subset of
these events it will be possible to directly `weigh' the star (or stellar
remnant) that is causing the lensing signal, either through higher order
microlensing effects and/or high-precision astrometric observations of the lens
star (using, for example, Gaia or SIM-lite). This means that such events could
play a crucial role in stellar astronomy. Given the current operational
timelines for Pan-STARRS and LSST, by the end of the decade they could
potentially detect up to 100 events. Although this is still too few events to
place detailed constraints on Galactic models, consistency checks can be
carried out and such samples could lead to exciting and unexpected discoveries.Comment: 11 pages, 8 figures. MNRAS (in press). Minor revisions according to
referee's report; mainly presentational issues and clarification of a few
items in the discussion; results and conclusions remain unchange
Polycystic ovary syndrome in patients with epilepsy: A study in 102 Chinese women
AbstractPurposeThe incidence of polycystic ovary syndrome (PCOS) increases in women with epilepsy (WWE), which appears to vary with ethnicity. This study was conducted to determine the incidence and risk factors of PCOS in Chinese WWE.MethodsThe study was carried out in 102 of 139 Chinese WWE at reproductive ages, with 32 receiving valproic acid (VPA), 40 receiving other antiepileptic drugs (AEDs), and 30 without AEDs therapy. PCOS was defined as having 2 or more of the following components: polycystic ovaries, hyperandrogenism, and amenorrhoea or oligomenorrhoea (a/oligomenorrhoea).ResultsOne or more isolated components of PCOS were found in 56 (54.9%) patients, with 29 (28.4%) having polycystic ovaries, 20 (19.6%) with a/oligomenorrhea, 7 (6.9%) with hyperandrogenism, and 13 (12.7%) with defined PCOS. Their average age at the start of seizure was 13.8±6.5years, younger than that of patients without these disorders (16.9±8.6years, p<0.05). VPA therapy increased the incidence of PCOS (11/32, 34.4%), in addition to increased blood levels of testosterone and luteinizing hormone (LH) as well as LH to FSH (follicle-stimulating hormone) ratio. No significant relationship was found between the incidence of PCOS and the type, duration, or frequency of seizures in these WWE.ConclusionThere is an increased incidence of PCOS in Chinese WWE at reproductive ages, by more than 2 times of that in the general population. Risk factors include seizures starting at a young age and VPA therapy
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