Vitamin C requirements in parenteral nutrition.

Some biochemical functions of vitamin C make it an essential component of parenteral nutrition (PN) and an important therapeutic supplement in other acute conditions. Ascorbic acid is a strong aqueous antioxidant and is a cofactor for several enzymes. The average body pool of vitamin C is 1.5 g, of which 3%-4% (40-60 mg) is used daily. Steady state is maintained with 60 mg/d in nonsmokers and 140 mg/d in smokers. Shocked surgical, trauma, and septic patients have a drastic reduction of circulating plasma ascorbate concentrations. These low concentrations require 3-g doses/d to restore normal plasma ascorbate concentrations, questioning the recommended PN dose of 100 mg/d. Determination of intravenous requirements is usually based on plasma concentrations, which are altered during the inflammatory response. There is no clear indicator of deficiency: serum or plasma ascorbate concentrations <0.3 mg/dL (20 micromol/L) indicates inadequate vitamin C status. On the basis of available pharmacokinetic data the 100 mg/d dose for patients receiving home PN and 200 mg/d for stable adult patients receiving PN are adequate, but requirements have been shown to be higher in perioperative, trauma, burn, and critically ill patients, paralleling oxidative stress. One recommendation cannot fit all categories of patients. Large vitamin C supplements may be considered in severe critical illness, major trauma, and burns because of increased requirements resulting from oxidative stress and wound healing. Future research should distinguish therapeutic use of high-dose ascorbic acid antioxidant therapy from nutritional PN requirements.

Nature versus nurture in social insect caste determination

Recent evidence for genetic effects on royal and worker caste differentiation from diverse social insect taxa has put an end to the view that these phenotypes stem solely from a developmental switch controlled by environmental factors. Instead, the relative influences of genotypic and environmental effects on caste vary among species, ranging from largely environmentally controlled phenotypes to almost purely genetic systems. Disentangling the selective forces that generate variation for caste predisposition will require characterizing the genetic mechanisms underlying this variation, and identifying particular life-history strategies and kin structures associated with strong genetic effects on caste.

Signaling cross-talk between peroxisome proliferator-activated receptor/retinoid X receptor and estrogen receptor through estrogen response elements.

Peroxisome proliferator-activated receptors (PPARs) and retinoid X receptors (RXRs) are nuclear hormone receptors that are activated by fatty acids and 9-cis-retinoic acid, respectively. PPARs and RXRs form heterodimers that activate transcription by binding to PPAR response elements (PPREs) in the promoter of target genes. The PPREs described thus far consist of a direct tandem repeat of the AGGTCA core element with one intervening nucleotide. We show here that the vitellogenin A2 estrogen response element (ERE) can also function as a PPRE and is bound by a PPAR/RXR heterodimer. Although this heterodimer can bind to several other ERE-related palindromic response elements containing AGGTCA half-sites, only the ERE is able to confer transactivation of test reporter plasmids, when the ERE is placed either close to or at a distance from the transcription initiation site. Examination of natural ERE-containing promoters, including the pS2, very-low-density apolipoprotein II and vitellogenin A2 genes, revealed considerable differences in the binding of PPAR/RXR heterodimers to these EREs. In their natural promoter context, these EREs did not allow transcriptional activation by PPARs/RXRs. Analysis of this lack of stimulation of the vitellogenin A2 promoter demonstrated that PPARs/RXRs bind to the ERE but cannot transactivate due to a nonpermissive promoter structure. As a consequence, PPARs/RXRs inhibit transactivation by the estrogen receptor through competition for ERE binding. This is the first example of signaling cross-talk between PPAR/RXR and estrogen receptor.

Determination of extreme floods using a distributed hydrological model

Hydrological models developed for extreme precipitation of PMP type are difficult to calibrate because of the scarcity of available data for these events. This article presents the process and results of calibration for a distributed hydrological model at fine scale developed for the estimation of probable maximal floods in the case of a PMP. This calibration is done on two Swiss catchments for two events of summer storms. The calculation done is concentrated on the estimation of the parameters of the model, divided in two parts. The first is necessary for the computation of flow speeds while the second is required for the determination of the initial and final infiltration capacities for each terrain type. The results, validated with the Nash equation show a good correlation between the simulated and observed flows. We also apply this model on two Romanian catchments, showing the river network and estimated flow.

Intervenció educativa basada en la promoció dels elements facilitadors del desenvolupament positiu de menors subjectes de mesures judicials

Al llarg dels darrers mesos i amb la participació de bona part del col·lectiu d’educadors i tècnics de medi obert del Departament de Justícia de la Generalitat de Catalunya, s’ha fet un treball d’aprofundiment entorn del paper que tenen els elements facilitadors del desenvolupament positiu dels joves que es troben en mesures penals juvenils, com a veritables desencadenants de processos de millora i d’inclusió social. Hem tractat de fer una classificació i guia per identificar aquests elements i una metodologia concreta per determinar-ne la presència o absència. Finalment, hem intentat, comptant amb l’experiència del col·lectiu , elaborar una guia d’eines i estratègies per a la promoció d’aquests elements positius, que poden afavorir el desenvolupament dels menors i facilitar la intervenció del tècnic. Després d’intensos i interessants debats sorgits en les aportacions al Fòrum del portal, i també en les reunions del grup d’entusiastes, hem acabat per definir el concepte, el que entenem, allò a què ens referim quan parlem d’elements facilitadors. És així que,finalment, els definirem com: Tots els recursos personals, familiars, socials i institucionals que promouen el desenvolupament exitós de l’adolescent, o bé que fan disminuir el risc d’aparèixer un desenvolupament alterat. La pretensió del “producte” elaborat no és constituir-se en un document de caràcter teòric, més aviat hem volgut donar-hi un sentit pràctic que l’apropi més a una eina de treball que no pas a un marc teòric de caire general. És per això que, un cop delimitat el concepte i els objectius del producte, el treball ha consistit en la relació i classificació d’aquests elements facilitadors del desenvolupament positiu que trobem en els menors i joves amb qui treballem, i en l’observació de la seva presència, absència o necessitat.

DNA binding properties of peroxisome proliferator-activated receptor subtypes on various natural peroxisome proliferator response elements. Importance of the 5'-flanking region.

The three subtypes of the peroxisome proliferator-activated receptors (PPARalpha, beta/delta, and gamma) form heterodimers with the 9-cis-retinoic acid receptor (RXR) and bind to a common consensus response element, which consists of a direct repeat of two hexanucleotides spaced by one nucleotide (DR1). As a first step toward understanding the molecular mechanisms determining PPAR subtype specificity, we evaluated by electrophoretic mobility shift assays the binding properties of the three PPAR subtypes, in association with either RXRalpha or RXRgamma, on 16 natural PPAR response elements (PPREs). The main results are as follows. (i) PPARgamma in combination with either RXRalpha or RXRgamma binds more strongly than PPARalpha or PPARbeta to all natural PPREs tested. (ii) The binding of PPAR to strong elements is reinforced if the heterodimerization partner is RXRgamma. In contrast, weak elements favor RXRalpha as heterodimerization partner. (iii) The ordering of the 16 natural PPREs from strong to weak elements does not depend on the core DR1 sequence, which has a relatively uniform degree of conservation, but correlates with the number of identities of the 5'-flanking nucleotides with respect to a consensus element. This 5'-flanking sequence is essential for PPARalpha binding and thus contributes to subtype specificity. As a demonstration of this, the PPARgamma-specific element ARE6 PPRE is able to bind PPARalpha only if its 5'-flanking region is exchanged with that of the more promiscuous HMG PPRE.

Determination of sea surface salinity and wind speed by L-band microwave radiometry from a fixed platform

The European Space Agency Soil Moisture andOcean Salinity (SMOS) mission aims at obtaining global maps ofsoil moisture and sea surface salinity from space for large-scale andclimatic studies. It uses an L-band (1400–1427 MHz) MicrowaveInterferometric Radiometer by Aperture Synthesis to measurebrightness temperature of the earth’s surface at horizontal andvertical polarizations ( h and v). These two parameters will beused together to retrieve the geophysical parameters. The retrievalof salinity is a complex process that requires the knowledge ofother environmental information and an accurate processing ofthe radiometer measurements. Here, we present recent resultsobtained from several studies and field experiments that were partof the SMOS mission, and highlight the issues still to be solved.

How do thyroid hormone receptors bind to structurally diverse response elements?

Three classes of thyroid hormone response elements have been described. They are composed of two half-sites arranged either as a palindromic, a direct repeat or as an inverted palindromic array. Receptor homodimers as well as heterodimers can bind to all three types of response element. While the ligand binding domain of the receptors provides the major dimerization surface, asymmetric contacts between the DNA binding domains are necessary for binding to a direct repeat. Moreover, some recent findings suggest that in TR, compared to RXR, the ligand binding domain has a 180 degrees rotation with respect to the DNA binding domain. This feature could explain the preferential binding of the RXR-TR heterodimer to the direct repeat response element, in which RXR exclusively binds the 5' half-site, and of the TR homodimer to the inverted palindrome response element.

Characterization of insulators and barrier elements for gene therapy

Gene transfer that relies on integrating vectors often suffers from epigenetic or regulatory effects that influence the expression of the therapeutic gene and=or of cellular genes located near the vector integration site in the chromosome. Insulator elements act to block gene activation by enhancers, while chromatin domain boundary or barrier sequences prevent gene-silencing effects. At present, the modes of action of insulator and barriers are poorly understood, and their use in the context of gene therapies remains to be documented. Using combinations of reporter genes coding for indicator fluorescent proteins, we constructed assay systems that allow the quantification of the insulator or barrier activities of genetic elements in individual cells. This presentation will illustrate how these assay systems were used to identify short DNA elements that insulate nearby genes from activation by viral vector elements, and=or that block the propagation of a silent chromatin structure that leads to gene silencing. We will show that some barrier elements do not merely block repressive effects, but that they can act to stabilize and sustain transgene expression. We will illustrate that this may be beneficial when transgenes are introduced into stem or precursor cells using non-viral vectors, where later differentiation may lead to the silencing of the therapeutic gene. We will show that these elements can be used to maintain efficient transgene expression upon the differentiation of murine precursor cells towards myofibers, in a model of cell therapy for muscle dystrophies.

In vivo fate mapping with SCL regulatory elements identifies progenitors for primitive and definitive hematopoiesis in mice.

One of the principal issues facing biomedical research is to elucidate developmental pathways and to establish the fate of stem and progenitor cells in vivo. Hematopoiesis, the process of blood cell formation, provides a powerful experimental system for investigating this process. Here, we employ transcriptional regulatory elements from the stem cell leukemia (SCL) gene to selectively label primitive and definitive hematopoiesis. We report that SCL-labelled cells arising in the mid to late streak embryo give rise to primitive red blood cells but fail to contribute to the vascular system of the developing embryo. Restricting SCL-marking to different stages of foetal development, we identify a second population of multilineage progenitors, proficient in contributing to adult erythroid, myeloid and lymphoid cells. The distinct lineage-restricted potential of SCL-labelled early progenitors demonstrates that primitive erythroid cell fate specification is initiated during mid gastrulation. Our data also suggest that the transition from a hemangioblastic precursors with endothelial and blood forming potential to a committed hematopoietic progenitor must have occurred prior to SCL-marking of definitive multilineage blood precursors.

Determination of plasma levels of citalopram and its demethylated and deaminated metabolites by gas chromatography and gas chromatography-mass spectrometry.

Sensitive and specific methods based on gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) for the determination of levels of citalopram, desmethylcitalopram and didesmethylcitalopram in the plasma of patients treated with citalopram are presented, as well as a GC-MS procedure for the assay of the citalopram propionic acid derivative. After addition of a separate internal standard for each drug, liquid-solvent extraction is used to separate the basic compounds from the acid compounds. The demethylated amines are derivatized with trifluoroacetic anhydride, and the acid metabolite with methyl iodide. GC-MS is performed in the electron impact mode, as mass spectrometry by the (positive-ion) chemical ionization mode (methane and ammonia) appeared to be unsuitable. The limits of quantification were 1 ng/ml for citalopram and desmethylcitalopram and 2 ng/ml for the other metabolites. The correlation coefficients for the calibration curves (range 10-500 ng/ml) were &gt; or = 0.999 for all compounds, whether determined by GC or GC-MS.

Sampling and TDR probe insertion in the determination of the volumetric soil water content

Volumetric soil water content (theta) can be evaluated in the field by direct or indirect methods. Among the direct, the gravimetric method is regarded as highly reliable and thus often preferred. Its main disadvantages are that sampling and laboratory procedures are labor intensive, and that the method is destructive, which makes resampling of a same point impossible. Recently, the time domain reflectometry (TDR) technique has become a widely used indirect, non-destructive method to evaluate theta. In this study, evaluations of the apparent dielectric number of soils (epsilon) and samplings for the gravimetrical determination of the volumetric soil water content (thetaGrav) were carried out at four sites of a Xanthic Ferralsol in Manaus - Brazil. With the obtained epsilon values, theta was estimated using empirical equations (thetaTDR), and compared with thetaGrav derived from disturbed and undisturbed samples. The main objective of this study was the comparison of thetaTDR estimates of horizontally as well as vertically inserted probes with the thetaGrav values determined by disturbed and undisturbed samples. Results showed that thetaTDR estimates of vertically inserted probes and the average of horizontally measured layers were only slightly and insignificantly different. However, significant differences were found between the thetaTDR estimates of different equations and between disturbed and undisturbed samples in the thetaGrav determinations. The use of the theoretical Knight et al. model, which permits an evaluation of the soil volume assessed by TDR probes, is also discussed. It was concluded that the TDR technique, when properly calibrated, permits in situ, nondestructive measurements of q in Xanthic Ferralsols of similar accuracy as the gravimetric method.

Effect of conditioned media, nutritive elements, and mitotic synchronization on the accuracy of the cytogenetic analysis in acute nonlymphocytic leukemia patients presenting with inv(16)/t(16;16) or t(15;17).

To improve the yield of the cytogenetic analysis in patients with acute nonlymphocytic leukemia (ANLL), six culture conditions for bone marrow or peripheral blood cells were tested in parallel. Two conditioned media (CM), phytohemagglutinin leukocyte PHA-LCM and 5637 CM, nutritive elements (NE), and methotrexate (MTX) cell synchronization were investigated in 14 patients presenting with either inv(16)/ t(16;16) (group 1, n = 9 patients) or t(15;17) (group 2, n = 5). The criteria used to identify the most favorable culture conditions were the mitotic index (MI), the morphological index (MorI), and the percentage of abnormal metaphases. In the presence of PHA-LCM and 5637 CM, the MI were significantly increased in group 2, whereas in the MTX conditions, MI remained very low in both groups. The values of the MorI did not reveal any significant changes in chromosome resolution between the conditions in either group. The addition of NE did not have a positive effect in quantity or quality of metaphases. Because of the variability of the response of leukemic cells to different stimulations in vitro, several culture conditions in parallel are required to ensure a satisfactory yield of the chromosome analysis in ANLL.