Extraction and identification of the hepatoprotective bio-active components of the root of Actinidia deliciosa

The root of Actinidia deliciosa has been used as traditional drugs in China for a long time. This study therefore aimed at investigating the hepatoprotective bio-active components from the root of A. deliciosa comprehensively and accurately, thus promoting the exploitation and utilization of the whole resource of A. deliciosa. For the purpose of this study, the roots of A. deliciosa were fractionated into various extract fractions with differential polarity solvent. The hepatoprotective activities of various solvent extracts were assessed by examining the effect on carbon tetrachloride (CCl4)-induced hepatotoxicity in rats. The highest hepatoprotective activities fraction was further isolated with column chromatography. The structures of the activities monomers were identified with modern spectrum technology such as infrared (IR), ultraviolet (UV), electron impact mass spectrometry (EI-MS), proton nuclear magnetic resonance (1H-NMR), carbon nuclear magnetic resonance (13C-NMR) and distortionless enhancement by polarization transfer-nuclear magnetic resonance (DEPT-NMR). Of the various extract fractions, the ethyl acetate extract (Fr3) exhibited the highest hepatoprotective activities (p<0.05). When the Fr3 was separated into five fractions by silica gel chromatography, among the five fractions fraction, Fr9 showed the highest yield and the highest hepatoprotective activities. When using Fr9 at a dose of 200 mg/kg to pre- and post-treat the CCl4-induced rat, the activities of alanine transaminase (ALT) decreased by 90.10 and 88.60%, aspartate transaminase (AST) decreased by 80.69 and 79.92% in rat serum, the lipid peroxidation (malondialdehyde (MDA)) decreased by 42.11 and 45.53%, while glutathione (GSH) increased by 114.12 and 147.62% in the rats liver homogenate, respectively as compared with that of the CCl4 control rats. The fraction Fr9 was further separated into five fractions using silica gel chromatography, which were investigated for the main chemical constituents by column chromatography techniques, physico-chemical constants and spectroscopic analysis. Its main chemical constituents were three triterpenoids named 3β-hydroxy-urs-12-en-28-oic acid (ursolic acid), 2α,3α,23-trihydroxy-urs-12-en-28-oic acid and 2α,3β,19,23-tetrahydroxy-urs-12-en-28-oic acid. The findings indicate that the high hepatoprotective activity of the fraction of A. deliciosa root is due to its enriched triterpenoid.Key words: Actinidia deliciosa root, carbon tetrachloride (CCl4), hepatoprotective, Chemistry

Whole cell screen for inhibitors of pH homeostasis in Mycobacterium tuberculosis

Bacterial pathogens like Mycobacterium tuberculosis (Mtb) encounter acidic microenvironments in the host and must maintain their acid-base homeostasis to survive. A genetic screen identified two Mtb strains that cannot control intrabacterial pH (pHIB) in an acidic environment; infection with either strain led to severe attenuation in mice. To search for additional proteins that Mtb requires to survive at low pH, we introduced a whole-cell screen for compounds that disrupt pHIB, along with counter-screens that identify ionophores and membrane perturbors. Application of these methods to a natural product library identified four compounds of interest, one of which may inhibit novel pathway(s). This approach yields compounds that may lead to the identification of pathways that allow Mtb to survive in acidic environments, a setting in which Mtb is resistant to most of the drugs currently used to treat tuberculosis

Ultrahigh-current-density niobium disulfide catalysts for hydrogen evolution

Metallic transition metal dichalcogenides (TMDs)1???8 are good catalysts for the hydrogen evolution reaction (HER). The overpotential and Tafel slope values of metallic phases and edges9 of two-dimensional (2D) TMDs approach those of Pt. However, the overall current density of 2D TMD catalysts remains orders of magnitude lower (~10???100 mA cm???2) than industrial Pt and Ir electrolysers (>1,000 mA cm???2)10,11. Here, we report the synthesis of the metallic 2H phase of niobium disulfide with additional niobium (2H Nb1+xS2, where x is ~0.35)12 as a HER catalyst with current densities of >5,000 mA cm???2 at ~420 mV versus a reversible hydrogen electrode. We find the exchange current density at 0 V for 2H Nb1.35S2 to be ~0.8 mA cm???2, corresponding to a turnover frequency of ~0.2 s???1. We demonstrate an electrolyser based on a 2H Nb1+ xS2 cathode that can generate current densities of 1,000 mA cm???2. Our theoretical results reveal that 2H Nb1+ xS2 with Nb-terminated surface has free energy for hydrogen adsorption that is close to thermoneutral, facilitating HER. Therefore, 2H Nb1+ xS2 could be a viable catalyst for practical electrolysers

Late Quaternary Climate History on the Northeast Tibetan Plateau: Multiproxy Investigation of Lake Qinghai Sediments, China

A dissertation submitted to the faculty of the Graduate School of the University of Minnesota by Xiuju Liu in partial fulfillment of the requirements for the degree of Doctor of Philosophy, September 2011. Advisors: Dr. Steven M. Colman, Dr. Erik T. Brown.The objective of this dissertation is to reconstruct the history of the Asian monsoon and to examine the controls of the climate system on the Tibetan Plateau, using lake sediment cores from Lake Qinghai, China. Lake Qinghai is the largest inland water body in China, situated on the northeastern margin of the Tibetan Plateau, where the climate conditions are mainly controlled by the interaction of the East Asian monsoon and the Westerlies. It lies near the limit of penetration of the Asian summer monsoon, and is thus sensitive to climate changes. Yet the climate history in this region is not fully understood. This dissertation contributes to our understanding of a detailed Holocene and late glacial climate history in western China. A set of Lake Qinghai sediment cores, including a 18.6-m-long drill core (LQDP05-1F), a 3.5-m-long Uwitec sediment core (QH07-1A), and a 0.85-m-long mini-Mackereth core (QH07-1B-1MM), provide a record of climate that extends further back in time than that from any other records for Lake Qinghai. Results from multiple proxies derived from the composite 2007 core (QH07) are internally consistent and reveal a distinct Holocene and Late Pleistocene climate record. Carbonate content and total organic carbon in sediments are interpreted as proxies for the strength of the Asian summer monsoon. During the glacial period (~14,600 to ~20,000 yrs), the summer monsoon intensity remained low and relatively constant, suggesting cool, dry, and relatively stable climatic conditions. The Holocene (~11,500 yrs to present) was a time of enhanced summer monsoon strength and greater variability, indicating relatively wetter but more unstable climatic conditions than those of the Late Pleistocene. The warmest, wettest part of the Holocene occurred from ~9,000 to ~11,500 yrs. The transition between the Holocene and the Late Pleistocene, about 11,500 years ago, was abrupt. A cool Younger Dryas appears to be recorded in the record, but its onset is not as distinct as it is in cave records from Dongge and Sanbao. Evidence of a warm interval correlative with the Bølling–Allerød oscillation is weak in the QH07 record. We propose that changes in the contrast of summer insolation between the continent and the ocean are the primary control on the Asian monsoon system over the glacial/interglacial time scales. Secondary influences may include ice sheet size (albedo) and sea level (distance from moisture source). A climate threshold for arrival of monsoonal rainfall is suggested at the northeastern Tibetan Plateau. Magnetic properties and geochemistry of sediments were determined for an 18.6 m uchannel sample of core LQDP05-1F and several selected discrete samples. These results provide clues to changes in magnetic mineral concentration, grain-size distribution, mineralogy, and geochemical composition, as well as having implications for paleoclimatology. The relative abundances of iron and concentration-dependent magnetic parameters reflect higher concentrations of magnetic minerals during glacial times than the Holocene. Hysteresis measurements of the discrete samples show larger proportions of single domain (SD) minerals relative to multiple domain (MD) particles in Late Pleistocene sediment compared to Holocene sediment, suggesting that the glacial period was dominated by deposition of fine-grained aeolian materials, whereas the Holocene was characterized by increased riverine transport of coarse materials to the lake. Furthermore, greater variability of magnetic parameters and geochemical composition during the Holocene suggests complex and multiple sediment sources. Magnetite has been identified as the primary ferrimagnetic mineral throughout the core, suggesting relatively constant mineralogy. Relatively low magnetite concentration during the Holocene is mainly due to dilution by increased authigenic carbonate that is strongly associated with riverine Ca delivery. The presence of monoclinic pyrrhotite implies reducing depositional environment associated with remineralization of organic matter in the lake. Several lines of evidence suggest the occurrence of greigite, which may indicate relatively dry climate conditions during the glacial period. Results from the elemental composition and magnetic properties of the Lake Qinghai sediments are consistent with records derived from lithological and sedimentological proxies. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Fluorescence (XRF) scanning techniques were evaluated, using sediments from Lake Qinghai and Lake Malawi (Africa). The results show statistically significant correlations between conventionally measured concentrations of carbonate (%CaCO3), total organic carbon (%TOC), and biogenic silica (%BSi), and absorbance in the corresponding FTIR spectral regions, as well as between conventional measurements and XRF elemental ratios including calcium: titanium (Ca/Ti), incoherent: coherent X-ray scatter intensities (Inc/Coh), and silicon: titanium (Si/Ti). Both FTIR and XRF techniques exhibit great potential to quantitatively assess concentrations of inorganic and organic components of lacustrine sediments. These results provide evidence that climate on the Tibetan Plateau has varied considerably, suggesting a relatively stable, cold, and dry Late Pleistocene along with a weak Asian summer monsoon, versus a relatively unstable, warm, and wet Holocene with a relatively strong summer monsoon. The results also highlight that the Asian monsoon system is driven by changes in the contrast of summer insolation between the continent and the ocean over the glacial/interglacial time scales

Darwin and Mendel today: A comment on Singh’s paper

We comment on a recent paper by Rama Singh, who concludes that Mendel deserved to be called the father of genetics, and Darwin would not have understood the significance of Mendel’s paper had he read it. We argue that Darwin should have been regarded as the father of genetics not only because he was the first to formulate a unifying theory of heredity, variation and development -- Pangenesis, but also because he clearly described almost all genetical phenomena of fundamental importance, including what he called “prepotency” and what we now call “dominance” or “Mendelian inheritance”. The word “gene” evolved from Darwin’s imagined “gemmules”, instead of Mendel’s so-called “factors”.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author