CLEAVAGE OF SEDOHEPTULOSE 1,7-DIPHOSPHATE BY A PURIFIED RAT LIVER DIPHOSPHATASE.

SUMMARY treatment. A simple procedure is described for the purification, from rat None of a variety of other monophosphate and diphosphate liver, of a diphosphatase activity which cleaves both fructose esters tested as substrates was cleaved by the purified enzyme diphosphate and sedoheptulose diphosphate to fructose 6-phos- at significant rates. These results suggest an absolute require- phate and sedoheptulose 7-phosphate, respectively. ment for the presence of two phosphate groups and also for the Evidence that a single enzyme is responsible for both reactions configuration found in FDP and SDP. n-Bibulose 1,5-diphos- is derived from the results of the purification steps, from kinetic phate differs in the configuration at C-3 and is not attacked. measurements, and from other properties. The enzyme has no With respect to the physiological role of the diphosphatase, activity with a variety of monophosphate esters and other di- although it has been generally recognized that fructose diphos- phosphate esters. phatase may represent a key enzyme in the synthesis of glycogen Both activities are present in the liver of all mammalian species from 3 carbon fragments, no direct evidence for a role of sedo- studied. heptulose diphosphatase has yet been obtained. REFERENCES Three possibilities may be considered with respect to the physiological significance of the latter activity. (a) It may be 1. GOMORI, G., J

A Direct Interconversion: d-Fructose 6-Phosphate Sedoheptulose 7-Phosphate and d-Xylulose 5-Phosphate Catalyzed by the Enzymes Transketolase and Transaldolase

n/

Crystalline D -Gluconate 6-Phosphate Dehydrogenase"

A method for t.he purification of n-gluconate 6-phosphate dchydrogenase from brewers' yeast has been described by Horecker and Smyrniotis. (1). The enzyme preparation also catalyzed the oxidation of n-glucose 6-phosphate and isocitrate and in addition contained significant amounts of n-ribose 5-phosphate isomerasc. The utility of the enzyme for the assay of n-gluconate 6-phosphato and for the preparation of n-ribulose 5-phosphate was seriously affected by the prcsencc of thcsc contaminating activitics. For a further investigation of the properties of the enzyme and of the nature of the two-step reaction, a more highly purified preparation was necessary. A method has now been developed which yields from Candida yeast a crystalline preparation which is free of detectable quantitics of I)-glucose 6-phosphata dchydrogenase and r)-ribose 5-phosphate isomerasc. To remove the former enzyme, advantage was taken of its lability to heat after treatment with charcoal (2, 3). n-Glucose 6-phosphate dchydrogcnasc is known to bc unstable in t,he absence of triphosphopyridine nuclcotidc. With the purified enzyme, only n-ribulosc 5-phosphate is formed, and this ester can thus be obtained free of n-ribose 5-phosphate and n-xylulose j-phosphate. Since the crystalline enzyme preparation catalyzes the osidation of reduced triphosphopyridine nucleotide by CO, and o-ribulose phosphate at a rate equal to that observed with crude enzyme preparations, wc have concluded that a single enzyme is rcsponsible for both oxidation and decarboxylation reactions. We have also undertaken an investigation of the specificity of the Mg++ requirement (1) and havn found that at high concentrations of NaCl, full activity is obtained in the absence of Mg++. There is reason to believe that the nature of t,he anion plays a role in the activation of the enzyme

Feminine Identities

The first four essays in this volume all focus on issues of gender in the works of different English authors and thinkers. Shorter versions of each of these essays were formerly presented as papers in an autonomous section of the Research and Educational Programme on Studies of Identity at the XXth Meeting of the Portuguese Association of Anglo-American Studies (Póvoa de Varzim, 1999) and published in the proceedings of the conference. The second cluster of essays in this volume — two of which (Jennie Wang’s and Teresa Cid’s) were first presented, in shorter versions, at the joint ASA/CAAS Conference (Montréal, 1999) — addresses the work of American women variously engaged in contexts of cultural diversity and grappling with the ideas of what it means to be an American and a woman, particularly in the twentieth century. These essays approach, from different angles, the definitional quandaries and semantic difficulties encountered when speaking about the self and the United States and provide, in one way or another, a sort of feminine rewriting of American myths and history.Fundação para a Ciência e a Tecnologi

Extracellular Vesicles in Biological Fluids. A Biomarker of Exposure to Cigarette Smoke and Treatment with Chemopreventive drugs

Extracellular vesicles (EVs) are released from cells and enter into body fluids thereby providing a toxicological mechanism of cell-cell communication. The present study aimed at assessing (a) the presence of EVs in mouse body fluids under physiological conditions, (b) the effect of exposure of mice to cigarette smoke for 8 weeks, and (c) modulation of smoke-related alterations by the nonsteroidal anti-inflammatory drug celecoxib, a selective cyclooxygenase-2 inhibitor. To this purpose, ICR (CD-1) mice were either unexposed or exposed to cigarette smoke, either treated or untreated with oral celecoxib. EVs, isolated from bronchoalveolar lavage fluid (BALF), blood serum, and urines, were analyzed by nanoparticle tracking analysis and flow cytometry. EVs baseline concentrations in BALF were remarkably high. Larger EVs were detected in urines. Smoking increased EVs concentrations but only in BALF. Celecoxib remarkably increased EVs concentrations in the blood serum of both male and female smoking mice. The concentration of EVs positive for EpCAM, a mediator of cell-cell adhesion in epithelia playing a role in tumorigenesis, was much higher in urines than in BALF, and celecoxib significantly decreased their concentration. Thus, the effects of smoke on EVs concentrations were well detectable in the extracellular environment of the respiratory tract, where they could behave as delivery carriers to target cells. Celecoxib exerted both protective mechanisms in the urinary tract and adverse systemic effects of likely hepatotoxic origin in smoke-exposed mice. Detection of EVs in body fluids may provide an early diagnostic tool and an end-point exploitable for preventive medicine strategies.

The generation of DNA single-strand breaks during the reduction of chromate by ascorbic acid and/or glutathione in vitro.

The potential role of iron and copper and the involvement of hydroxyl radicals in the DNA cleavage caused by chromate and glutathione (GSH) has been investigated. We have also studied the ability of chromate, on reaction with ascorbate as well as in mixed solutions of ascorbate and GSH, to cause DNA strand breaks. In both fully demetalated and conventional (i.e., metal contaminated) systems, chromate and GSH induced similar numbers of DNA strand breaks. This observation suggests that traces of iron or copper contaminating the reaction mixtures do not play a major role in the DNA cleavage caused by chromate and GSH. A series of hydroxyl radical scavengers exhibited a protective influence on the induction of DNA strand breaks. However, glucose and sucrose, both strong hydroxyl radical scavengers, showed no concentration-dependent inhibition of DNA cleavage. Competition kinetics studies yielded apparent rate constants that were not consistent with hydroxyl radicals being the species responsible for DNA strand breaks. Ascorbate in combination with chromate was also found to induce strand breaks in DNA; this damage could be attributed to reactive intermediates generated during the reduction. When mixed systems of ascorbate and GSH in the presence of chromate were investigated, there were clearly interactions between the two reductants

Montelukast therapy and psychological distress in chronic obstructive pulmonary disease (COPD): a preliminary report

Chronic obstructive pulmonary disease (COPD) is an alteration in which ventilatory function, exercise capacity and health status of patients progressively decline and it is characterized by an increase of inflammatory cytokines such as TNF-a, LTB4, IL-8, etc. In this study we considered twenty patients (15 males and 5 females; mean age: 72.8 6.3) with stable COPD. All patients were performed evaluation of psychological stress at enrollment and were treated with leukotriene receptor antagonists (montelukast tablets) 10 mg/day for 12 months. After 12 months we observed a significant decrease of serum levels of LTB4, IL-8 and also a decrease of the number of outpatient clinic visits, of the number of hospitalizations and of the duration of hospitalizatio