Synthesis of glucuronides in liver homogenates

From a chemical point of view, glucuronic acid may be regarded as a derivative of glucose in which the primary alcoholic group has been oxidised, producing a carboxylic acid. The chemical properties of glucuronic acid have as yet been relatively little studied, but like all substances bearing a potentially reducing aldehyde group, it will form glycosides, and these 'conjugated' compounds, without reducing properties, are known as glucuronides.In living organisms, glucuronic acid is found almost entirely in the conjugated form, and, although very widely distributed, remarkably little is known about its physiological function. As the great importance of the compound can be inferred from such widespread occurrence we may, before considering the various theories regarding its biosynthesis, briefly indicate the natural distribution of glucuronic acid.The work presented below was begun with the intention of studying further the nature of glucuronide synthesis in the liver, using disintegrated cell preparations (the so- called 'homogenates'); the use of such preparations is the next logical step after slice experiments, for it enables more consistent conditions to be attained, and prepares for eventual enzyme isolation.In place of the overall results which are all that can be ascertained from experiments on whole animals, the homogenate technique offers a simple and convenient method of directly demonstrating definite reactions, such as the production of o-aminophenylglucuronide on adding o-aminophenol. Whereas with the intact animal, its perfused organ or even slices of that organ, there is no certainty that the added substance is really reaching the responsible enzymes, or in what form or concentration it might do so, in the homogenate technique a much closer control can be exercised. The problems of diffusibility of substrate and inhibitors through the cell membrane, or of unequal tissue thicknesses with their consequent metabolic differences, do not exist in homogenates, where, provided reasonably complete cell disruption has occurred, equal volumes of the tissue preparation will behave identically, being to the same degree exposed to their environment. If the homogenate be used in a sufficiently dilute form, autolysis will be checked and by the addition of various metabolites and cofactors the enzyme system of part or all of the desired reaction may be encouraged above the level of others; subsequently the studied system may be isolated from the crude homogenate and its behaviour controlled to an extent impossible by any other means.Therefore, since liver slices had already been used by Storey to investigate the biosynthesis of glucuronides, liver homogenates were employed in the present work, which continues the study of glucuronic acid conjugation in the liver.It was found during the course of this work that appreciable glucuronide formation could be obtained in liver homogenates, but only when a boiled liver extract was added to the medium (Dutton & Storey, 1951). The bulk of this work, then, concerns the isolation and purification of the substance responsible, and the behaviour of the enzyme system utilising it (Dutton & Storey, 1953).After the tabulation of the various standard methods used, there follows a report of the experimental results, showing how, despite the trial of many compounds of metabolic importance, no significant synthesis was obtained unless a boiled liver extract containing the unknown factor was added. Evidence that the products of synthesis were indeed glucuronides is given, and a few observations on the homogenate enzyme are appended. Work on the nature of this synthesis with the crude factor is then described, and the dissimilarity of the system to that obtaining with sliced tissue (Storey, 1950) pointed out. Lastly, the course of isolation and purification of the factor is illustrated, with its analysis and structural investigation. In the Discussion the relationship of this work to the results of previous investigators will be dealt with, and its bearing on the wider aspects of glucuronic acid metabolism indicated

Vertical Transport Rates in the Stratosphere in 1993 from Observations of CO2, N2O and CH4

Measurements of CO2, N2O and CH4 are analyzed to define hemispheric average vertical exchange rates in the lower stratosphere from November 1992 to October 1993. Effective vertical diffusion coefficients were small in summer, less than or equal to 1 m(exp 2)/sec at altitudes below 25 km; values were similar near the tropopause in winter, but increased markedly with altitude. The analysis suggests possibly longer residence times for exhaust from stratospheric aircraft, and more efficient transport from 20 km to the middle stratosphere, than predicted by many current models. Seasonally-resolved measurements of stratospheric CO2 and N2O provide significant new constraints on rates for global-scale vertical transport

Touchscreen performance and knowledge transfer in the red-footed tortoise (Chelonoidis carbonaria)

In recent years red-footed tortoises have been shown to be proficient in a number of spatial cognition tasks that involve movement of the animal through space (e.g., the radial maze). The present study investigated the ability of the tortoise to learn a spatial task in which the response required was simply to touch a stimulus presented in a given position on a touchscreen. We also investigated the relation between this task and performance in a different spatial task (an arena, in which whole-body movement was required). Four red-footed tortoises learned to operate the touchscreen apparatus, and two learned the simple spatial discrimination. The side-preference trained with the touchscreen was maintained when behaviour was tested in a physical arena. When the contingencies in the arena were then reversed, the tortoises learned the reversal but in a subsequent test did not transfer it to the touchscreen. Rather they chose the side that had been rewarded originally on the touchscreen. The results show that red-footed tortoises are able to operate a touchscreen and can successfully solve a spatial two-choice task in this apparatus. There was some indication that the preference established with the touchscreen could transfer to an arena, but with subsequent training in the arena independent patterns of choice were established that could be evoked according to the test context

Complete genome sequence of Candidatus Ruthia magnifica

The hydrothermal vent clam Calyptogena magnifica (Bivalvia: Mollusca) is a member of the Vesicomyidae. Species within this family form symbioses with chemosynthetic Gammaproteobacteria. They exist in environments such as hydrothermal vents and cold seeps and have a rudimentary gut and feeding groove, indicating a large dependence on their endosymbionts for nutrition. The C. magnifica symbiont, Candidatus Ruthia magnifica, was the first intracellular sulfur-oxidizing endosymbiont to have its genome sequenced (Newton et al. 2007). Here we expand upon the original report and provide additional details complying with the emerging MIGS/MIMS standards. The complete genome exposed the genetic blueprint of the metabolic capabilities of the symbiont. Genes which were predicted to encode the proteins required for all the metabolic pathways typical of free-living chemoautotrophs were detected in the symbiont genome. These include major pathways including carbon fixation, sulfur oxidation, nitrogen assimilation, as well as amino acid and cofactor/vitamin biosynthesis. This genome sequence is invaluable in the study of these enigmatic associations and provides insights into the origin and evolution of autotrophic endosymbiosis

1688 and All That: Property Rights, the Glorious Revolution and the Rise of British Captialism

COPYRIGHT: © Millennium Economics Ltd 2016 This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.In a seminal 1989 article, Douglass North and Barry Weingast argued that by making the monarch more answerable to Parliament, the Glorious Revolution of 1688 helped to secure property rights in England and stimulate the rise of capitalism. Similarly, Daron Acemoglu, Simon Johnson, and James Robinson later wrote that in the English Middle Ages there was a ‘lack of property rights for landowners, merchants and proto-industrialists’ and the ‘strengthening’ of property rights in the late 17th century ‘spurred a process of financial and commercial expansion’. There are several problems with these arguments. Property rights in England were relatively secure from the 13th century. A major developmental problem was not the security of rights but their feudal nature, including widespread ‘entails’ and ‘strict settlements’. 1688 had no obvious direct effect on property rights. Given these criticisms, what changes promoted the rise of capitalism? A more plausible answer is found by addressing the post-1688 Financial and Administrative Revolutions, which were pressured by the enhanced needs of war and Britain's expanding global role. Guided by a more powerful Parliament, this new financial system stimulated reforms to landed property rights, the growth of collateralizable property and saleable debt, and thus enabled the Industrial Revolution.Peer reviewedFinal Published versio

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Australia's last explorer : Ernest giles

175 p.; 20 cm