Lipid Peroxidation. Definition of Experimental Conditions for Selective Study of the Propagation and Termination Phases

1989 ◽  
Vol 5 (4-5) ◽  
pp. 245-252 ◽  
Author(s):  
Bruna Tadolini ◽  
Diana Fiorentini ◽  
Laura Landi ◽  
Luciana Cabrini
Keyword(s):  
Lipid Peroxidation ◽  
Experimental Conditions ◽  
Definition Of

Determination of the aluminium complexing capacity of fulvic acids and natural waters, with examples from five New Zealand rivers

1996 ◽  
Vol 47 (1) ◽  
pp. 11 ◽  
Author(s):  
DJ Hawke ◽  
KJ Powell ◽  
JE Gregor
Keyword(s):  
Reaction Time ◽  
Natural Waters ◽  
Fulvic Acids ◽  
Operational Definition ◽  
Experimental Conditions ◽  
River Waters ◽  
Complexation Capacity ◽  
Complexing Capacity ◽  
Definition Of

An FIA technique with 7 s reaction time was used to analyse free plus labile Al in fulvic acid (FA) solutions and natural waters at pH 4.7, without the need for separation procedures. Titrations of these solutions using incremental pH or total Al were used to determine pH binding curves or estimates of the 'kinetic' Al complexation capacity (Al-CCk) respectively. The operational definition of Al-CCk relates to the capacity of a humic substance or natural water to bind Al through a 7-s FIA reaction time under defined experimental conditions of chromophore (CAS) concentration, ionic strength, and pH. Both Al binding strength and complexation capacity were greater than the corresponding Cu-CC (ISE) values. The Al-CCk measurements at pH 4.7 were 710 μmol Al g-1 v. 590 μmol Cu g-1. Al-CCk results (pH 4.7) were higher for soil FA (710 μmol g-1) than for aquatic FA (390 μmol g-1). Al-CCk results (pH 4.7) for five unfiltered river waters from different catchments gave results in the range 6.5-9.8 μmol Al L-1. The differences between total (natural) Al in the samples and Al-CCk were between 2.7 μM and 8.6 μM. Filtration experiments identified fractionation patterns between total (natural) Al and the fraction of Al-CCk not utilized. The Al titration of alginate, another component of natural organic matter, is reported.

Effect of ethanol on the glucose-induced movements of protons across the plasma membrane of Saccharomyces cerevisiae NCYC 431

1987 ◽  
Vol 33 (2) ◽  
pp. 93-97 ◽  
Author(s):  
Jean-Regis Juroszek ◽  
Michel Feuillat ◽  
Claudine Charpentier
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Ethanol Tolerance ◽  
Ethanol Concentration ◽  
Effect Of Temperature ◽  
Proton Efflux ◽  
Experimental Conditions ◽  
Growth Cessation ◽  
A New Technique ◽  
Definition Of

The study of glucose-induced proton fluxes in Saccharomyces cerevisiae NCYC 431 showed a decrease of proton net efflux by ethanol across the plasma membrane of energized cells. Furthermore a negative net proton efflux (an influx) occurred from a given ethanol concentration (between 1.3 and 1.5 M) whatever the experimental conditions used, thus allowing the definition of a nil–net exchange step where no net movement of protons across the plasma membrane could be observed. A new technique of ethanol tolerance determination in yeast based upon a correlation for the same ethanol concentration between both the collapse of the proton gradient and the growth cessation in cultures supplemented with ethanol after 8 h incubation was proposed. The defined method also showed a cumulated effect of temperature and ethanol on Saccharomyces cerevisiae NCYC 431.

Contrast analysis of the composition of ribosomes extracted with different purification procedures

2000 ◽  
Vol 33 (4) ◽  
pp. 1113-1118 ◽  
Author(s):  
Giuseppe Briganti ◽  
Rita Giordano ◽  
Paola Londei ◽  
Francesco Valle
Keyword(s):  
Particle Density ◽  
Buoyant Density ◽  
Bulk Water ◽  
Water Molecules ◽  
Experimental Conditions ◽  
Reliable Technique ◽  
E Coli ◽  
Contrast Analysis ◽  
Definition Of ◽  
Contour Surface

The composition and hydration ofE. coliribosomes isolated with different purification protocols has been analysed by combining two experimental techniques: measurements of small-angle neutron scattering (SANS), for two different isotopic solvent compositions, and refractive index (RI) increments. From the contrast between the solvent and solute scattering densities and the molar polarizability, determined experimentally with SANS and RI measurements, three independent equations are obtained and three unknown quantities are determined: (i) the volume of the solute hydrated skeletonVs, (ii) the material contained in it, namely the biological components, intrinsic (rRNA and proteins) and extrinsic, such as aminoacylsynthetase and elongation factors, (iii) the number of water molecules structurally bound to the ribosome and non-exchangeable with the solvent. From the form factor at infinite contrast, a second definition of the solute volume is obtained, V_s^c, which represents the volume within the contour surface of the ribosome. This value is generally larger thanVsand can include a certain amount of water molecules,i.e.those inside the volume (V_s^c −Vs). Considering the molar volume of this water to be equal to that of the bulk water, it is possible to evaluate its amount. The particle density calculated from the ribosome components in V_s^c, including proteins, RNA, bound and unbound water molecules, corresponds to the buoyant density measured forE. coli70S particles. The two ribosomal preparations display different performances in protein synthesis; hence the results indicate that the optimal condition corresponds to a wider skeleton and contour volume but containing a smaller amount of segregated water molecules. It is believed that the method provides a reliable technique to determine the composition of ribosomes under various experimental conditions.

Selected Contribution: Ambient temperature for experiments in rats: a new method for determining the zone of thermal neutrality

2002 ◽  
Vol 92 (6) ◽  
pp. 2667-2679 ◽  
Author(s):  
Andrej A. Romanovsky ◽  
Andrei I. Ivanov ◽  
Yury P. Shimansky
Keyword(s):  
Ambient Temperature ◽  
Body Core Temperature ◽  
Body Parts ◽  
Experimental Conditions ◽  
Strong Negative Correlation ◽  
Liquid Crystal Thermography ◽  
Body Core ◽  
Definition Of ◽  
Operational Range ◽  
Rat Tail

There is a misbelief that the same animal has the same thermoneutral zone (TNZ) in different experimental setups. In reality, TNZ strongly depends on the physical environment and varies widely across setups. Current methods for determining TNZ require elaborate equipment and can be applied only to a limited set of experimental conditions. A new, broadly applicable approach that rapidly determines whether given conditions are neutral for a given animal is needed. Consistent with the definition of TNZ [the range of ambient temperature (Ta) at which body core temperature (Tc) regulation is achieved only by control of sensible heat loss], we propose three criteria of thermoneutrality: 1) the presence of high-magnitude fluctuations in skin temperature (Tsk) of body parts serving as specialized heat exchangers with the environment (e.g., rat tail), 2) the closeness of Tsk to the median of its operational range, and 3) a strong negative correlation between Tskand Tc. Thermocouple thermometry and liquid crystal thermography were performed in five rat strains at 13 Ta. Under the conditions tested (no bedding or filter tops, no group thermoregulation), the Ta range of 29.5–30.5°C satisfied all three TNZ criteria in Wistar, BDIX, Long-Evans, and Zucker lean rats; Zucker fatty rats had a slightly lower TNZ (28.0–29.0°C). Skin thermometry or thermography is a definition-based, simple, and inexpensive technique to determine whether experimental or housing conditions are neutral, subneutral, or supraneutral for a given animal.

How Does Communicating Herd Immunity Affect Immunization Intentions?

2021 ◽  
Vol 10 (4) ◽  
pp. 12-20
Author(s):  
Sandro Stoffel ◽  
Benedikt Herrmann
Keyword(s):  
Influenza Virus ◽  
Herd Immunity ◽  
Social Benefit ◽  
European Countries ◽  
Experimental Conditions ◽  
Vignette Study ◽  
The Social ◽  
Country Differences ◽  
Cross Country ◽  
Definition Of

While previous studies have shown that communicating herd immunity can increase immunization intentions, it is unclear how the definition of the beneficiaries influences intentions. In a vignette study, using a new hypothetical influenza virus, 4,172 participants from five European countries (Bulgaria, N=873; Denmark, N=896; England, N=873; Estonia, N=916; and Italy, N=745) were randomized to one of three experimental conditions: (1) control (no mention of herd immunity), (2) society (social benefit of immunization for overall society mentioned), and (3) friends (social benefit for friends and family members mentioned). While the study did not find that communicating herd immunity influenced overall immunization intentions across the five countries, it found substantial cross-country differences in the effect of the communication. In England, friends increased intentions, while society increased intentions in Denmark but decreased it in Italy. While communicating the social benefit of immunization can influence intentions, its contrasting effects highlight the importance of empirically testing.

Further Observations on the Fine Structure of Freeze-Cleaved Tight Junctions

1973 ◽  
Vol 13 (3) ◽  
pp. 763-786 ◽  
Author(s):  
L. A. STAEHELIN
Keyword(s):  
Fine Structure ◽  
Tight Junction ◽  
Tight Junctions ◽  
Plasma Membranes ◽  
Central Area ◽  
Experimental Conditions ◽  
Cellular Space ◽  
Mesh Work ◽  
Definition Of ◽  
Sealing Elements

The fine structure of freeze-cleaved tight junctions has been examined in high-resolution replicas of rat small intestine. By carefully comparing the changes in the surface topography of the cleavage faces of specimens, which, before freezing, were either prefixed with glutaraldehyde and then infiltrated with glycerol, infiltrated with glycerol alone, or infiltrated with glycerol and then fixed with glutaraldehyde, a more precise definition of the tight-junction architecture at the supramolecular level has become possible. The results of this analysis suggest that the bilayer membranes contributing to a tight junction are held together along inter-connected lines of attachment that are arranged in the form of a continuous band-like mesh-work. Each line consists of 2 parallel rows, one in each membrane, of closely spaced adhesion particles. The sensitivity of these particles to glutaraldehyde and their cleaving behaviour under different experimental conditions indicate that they represent globular proteins which bridge the width of the adjoining membranes and are linked together in the plane of the inter-cellular space. Thus, the morphology of a tight-junction seal resembles a modified zipper with the locking units making head to head contact. Similarly, the presence of many open-ended sealing elements between crypt cells has been interpreted as suggesting that the formation of tight-junction seals could resemble a ‘zippering-up’ process. At the juncture of 3 cells the tight-junction meshwork is both modified and extended basally to produce a characteristic pattern. In the central area of such a triple junction, 3 parallel and very closely spaced vertical seals have been resolved, each joining a pair of adjacent plasma membranes. Small, regularly spaced, cross-bridging elements interlink pairs of central seals within the plane of each membrane. At different levels each individual central seal may further give rise to horizontal sealing elements which connect in a ladder-like fashion either to the major network or to vertical elements positioned at greater distances from the central axis. Evidence is presented suggesting that fragments of tight junctions can be internalized and broken down in lysosome-like vesicles.

scholarly journals Characterization of Specific Protein-RNA Complexes Associated with the Coupling of Polyadenylation and Last-Intron Removal

2002 ◽  
Vol 22 (13) ◽  
pp. 4579-4586 ◽  
Author(s):  
Charles Cooke ◽  
James C. Alwine
Keyword(s):  
Specific Protein ◽  
Polyadenylation Signal ◽  
Site Formation ◽  
Coupling Mechanism ◽  
Experimental Conditions ◽  
Specific Complex ◽  
Intron Removal ◽  
Definition Of ◽  
Rna Complexes

ABSTRACT Polyadenylation and splicing are highly coordinated on substrate RNAs capable of coupled polyadenylation and splicing. Individual elements of both splicing and polyadenylation signals are required for the in vitro coupling of the processing reactions. In order to understand more about the coupling mechanism, we examined specific protein-RNA complexes formed on RNA substrates, which undergo coupled splicing and polyadenylation. We hypothesized that formation of a coupling complex would be adversely affected by mutations of either splicing or polyadenylation elements known to be required for coupling. We defined three specific complexes (AC′, AC, and BC) that form rapidly on a coupled splicing and polyadenylation substrate, well before the appearance of spliced and/or polyadenylated products. The AC′ complex is formed by 30 s after mixing, the AC complex is formed between 1 and 2 min after mixing, and the BC complex is formed by 2 to 3 min after mixing. AC′ is a precursor of AC, and the AC′ and/or AC complex is a precursor of BC. Of the three complexes, BC appears to be a true coupling complex in that its formation was consistently diminished by mutations or experimental conditions known to disrupt coupling. The characteristics of the AC′ complex suggest that it is analogous to the spliceosomal A complex, which forms on splicing-only substrates. Formation of the AC′ complex is dependent on the polypyrimidine tract. The transition from AC′ to AC appears to require an intact 3′-splice site. Formation of the BC complex requires both splicing elements and the polyadenylation signal. A unique polyadenylation-specific complex formed rapidly on substrates containing only the polyadenylation signal. This complex, like the AC′ complex, formed very transiently on the coupled splicing and polyadenylation substrate; we suggest that these two complexes coordinate, resulting in the BC complex. We also suggest a model in which the coupling mechanism may act as a dominant checkpoint in which aberrant definition of one exon overrides the normal processing at surrounding wild-type sites.

X Ray Spectra Simulation For Wds : Application to Electron Microprobe Automation

2001 ◽  
Vol 7 (S2) ◽  
pp. 674-675
Author(s):  
C. Fournier ◽  
P.-F. Staub ◽  
C. Merlet
Keyword(s):  
Electron Microprobe ◽  
Efficiency Function ◽  
Experimental Conditions ◽  
X Ray ◽  
Absolute Intensities ◽  
Definition Of ◽  
Short Time ◽  
New Generation ◽  
Excitation Conditions ◽  
A Current

Experimental conditions and setting up of an electron microprobe is directly linked to the assumption or the knowledge that can make the operator on the results of the measurements. Consequently, there is an increasing interest in modelling the X-ray spectrum in order to predict accurately and rapidly the response of the microprobe when a sample of approximately known composition is submitted to specific excitation conditions. Even if the spectra simulation is a current tool proposed in EDS, it always remains a challenge to create a complete absolute WDS spectrum. Indeed, the definition of the efficiency function was a limit to the calculation of absolute intensities.In this work, we propose a new generation software for EPMA which uses the absolute simulation spectra to assist the operator in the choices of experimental conditions to achieve accurate measurements in a short time as well as to create new functionalities.

On the cellular patterns in thermal convection

1964 ◽  
Vol 18 (4) ◽  
pp. 481-498 ◽  
Author(s):  
J. T. Stuart
Keyword(s):  
Mathematical Model ◽  
Convective Motion ◽  
Theoretical Work ◽  
Experimental Conditions ◽  
Cellular Pattern ◽  
Precise Knowledge ◽  
A Cell ◽  
Definition Of ◽  
New Formulation ◽  
The Mathematical Model

In the theory of thermal convective instability between two horizontal planes there are many solutions that are periodic in the horizontal co-ordinates, while in experiment convection is observed to take place in cellular patterns. It is often assumed, or decided after insufficient argument, that the periodic solutions of the mathematical model ‘explain’ or correspond to these patterns, but a completely satisfactory discussion of this correspondence has not been given. Indeed, with certain mathematical solutions ambiguities arise as to what cell centres and cellular boundaries are. A detailed discussion has recently become especially necessary because attempts are being made to predict which particular cellular pattern will occur in given experimental conditions.In this paper the topic is studied afresh and the question is asked: what features, in the mathematical model, correspond to what an experimentalist observes in cellular convective motion? In answer a definition of a cell is formulated which relates certain surfaces in the flow field of the mathematical model to steady vertical cellular boundaries that are observed in experiment, and which shows where the cell centres lie. In particular the classical hexagonal cellular pattern, of the mathematical model, is shown to be the prototype pattern of what is experimentally observed. On the other hand the square and so called ‘rectangular’ cases of linearized theory are shown not to correspond truly to square and rectangular cells at all. The new formulation is especially relevant to theoretical work on the prediction of cell shape and direction of flow in cells, since precise knowledge of the shapes of the cellular boundaries and locations of cell centres is essential if predictions are to be compared with observation.

The effects of subchronic lithium administration in male Wistar mice on some biochemical parameters

2009 ◽  
Vol 28 (10) ◽  
pp. 641-646 ◽  
Author(s):  
R. Nciri ◽  
MS Allagui ◽  
C. Vincent ◽  
JC Murat ◽  
F. Croute ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Body Weight ◽  
Weight Gain ◽  
Biochemical Parameters ◽  
Lithium Treatment ◽  
Lithium Carbonate ◽  
Prolonged Treatment ◽  
Plasma Testosterone ◽  
Experimental Conditions ◽  
Antioxidative Status

Lithium salts are efficiently used for treatment of psychiatric disorders. However, prolonged treatment frequently involves adverse side effects. In this study, effects of lithium carbonate administration on some biochemical parameters were studied in male mice. Lithium carbonate (20, 40, or 80 mg/kg body weight corresponding to 3.77, 7.54, or 15.08 mg Li element/kg body weight, respectively) was injected daily for 14 or 28 days. The following parameters were recorded: drinking water consumption, body weight, lithium and testosterone serum concentrations, activities of catalase (CAT), superoxide-dismutase (SOD), and glutathione-peroxidase (GPX), and level of lipid peroxidation (expressed as TBARS) in liver was performed. Lithium treatment, especially at the highest dose for 28 days, was found to induce weight gain and polydipsia and a significant decrease of plasma testosterone level. Lipid peroxidation level and activities of SOD and GPX were increased in liver, which suggests a perturbation of the antioxidative status. Our results indicate that subchronic exposure to lithium, which induces weight gain and polydipsia under our experimental conditions, also damages the male reproductive system and triggers an oxidative stress in the liver.

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