Summary
Current models of soil organic carbon (SOC) include a passive pool representing refractory soil organic matter (RSOM) with turnover times of hundreds to thousands of years. These models ...suggest that, as total soil C is depleted, it becomes proportionally enriched in RSOM. The objectives of our study were to quantify clay‐associated organic matter resistant to peroxide treatment in soils presumed to have differing proportions of RSOM, hypothesizing that peroxide‐resistant C in the clay fraction belongs to RSOM, and that its proportion will increase with total C depletion. Clay fractions (< 2 µm) from three soils from a cultivation sequence, differing in the duration of cultivation, one long‐term cultivated soil and one long‐term bare fallow soil corresponded to samples increasingly depleted in total organic C. Samples were suspended in 30% hydrogen peroxide and treated until no changes in C concentration were observed. Total C in the clay‐peroxide suspensions decreased exponentially and displayed kinetics corresponding to labile, intermediate and peroxide‐resistant pools. Carbon isotope analyses showed an enrichment of 13C in samples after peroxide treatment, compared with before, that decreased from 8‰ in forest samples to 0‰ in long‐term bare fallow. The proportion of peroxide‐resistant C did not differ between soils and represented 12% of initial clay‐associated organic C. No proportional increase with soil C depletion was observed and when expressed on a whole‐soil basis, the results underestimated proposed values for the RSOM pool, suggesting that peroxide treatment may not be appropriate for the estimation of the RSOM pool.
Oxydation à l'eau oxygénée de la matière organique de la fraction argiles des sols d'une chronosequence de mise en culture
Résumé
Les modèles actuels de la dynamique du carbone dans les sols prévoient un compartiment de carbone stable, caractérisé par des temps de renouvellement de l'ordre du siècle au millénaire. Ces modèles suggèrent que si les sols s'appauvrissent en carbone, ils devraient proportionnellement s'enrichir en carbone stable. Nous avons fait l'hypothèse qu'une partie de ce carbone stable était présent dans des matières organiques résistantes à l'eau oxygénée de la fraction argiles des sols (< 2 µm). Ce travail avait donc pour objectif de quantifier ces matières organiques, dans des sols correspondant à une gamme de teneurs en carbone décroissantes: trois sols provenant d'une chronoséquence de mise en culture, différant par la durée de la culture, un sol cultivé depuis de nombreuses années, et un sol provenant d'un essai de longue durée en jachère nue. Les fractions < 2 µm de ces sols ont été agitées en suspension dans des solutions d'eau oxygénée (30%) jusqu'à ce que leur teneur en carbone se stabilise. Les teneurs en carbone des fractions ont diminué suivant une loi exponentielle et nous avons distingué des compartiments labile, moyennement résistants et stables vis à vis de l'oxydation à H2O2. La fraction résistante à l'eau oxygénée était généralement enrichie en 13C de 0‰ (jachère nue) à 8‰ (sol sous forêt). La proportion de C résistant à l'eau oxygénée s'est avérée être constante et égale 12% du carbone des fractions < 2 µm pour les différents sols. Le fait que la proportion de C résistant à l'eau oxygénée dans les fractions argile n'augmente pas avec l'appauvrissement en C des sols, tend à montrer que cette méthode ne permet pas d'isoler le carbone stable des sols.
Primary organo-mineral complexes are defined as organic matter (OM) bound to primary mineral particles, isolated after complete dispersion of soil. Organic matter present in < 2 μm particle-size ...fractions of soils has slow turnover times and it is assumed to be stabilized mainly by interaction with minerals. We aimed to quantify how much of the organic matter in < 2 μm particle-size fractions was free versus bound to minerals and to describe the nature of the association. Furthermore, we hypothesized that this bound organic matter was more resistant to biodegradation than free organic particles. We tested this by using a cultivation chronosequence on temperate silty soils and quantified free and clay-bound organic matter using density fractionation coupled with elemental analyses, as well as transmission electron microscopy (TEM) coupled with image analyses. Both methods showed that free organic matter was a minor fraction and that it was more depleted by cultivation than clay-bound organic matter. We deduced that clay-bound organic matter was more resistant to biodegradation. TEM showed that the distribution of organic matter in clay-sized fractions was patchy and that many of the so-called < 2 μm 'particles' were in fact nanometre- to micrometre-sized microaggregates in which OM was encrusted by minerals or coated minerals. We conclude that true primary organo-mineral complexes do not correspond to reality and must be regarded as conceptual entities. We suggest that the very small microaggregates, which were evidenced here, are major sites of OM stabilization, both by adsorption and by entrapment of organic matter.
Land use changes result in significant decreases in soil organic matter stocks due to enhanced mineralization attributed to increased tillage, and due to decreased organic matter inputs. The current ...paradigm of soil organic matter dynamics suggests that decreasing organic matter stocks are also associated with shifts in organic matter quality to more resistant fractions as the more labile pools are decomposed. The objectives of the current study were to characterize changes in clay-associated organic matter quality in a soil C depletion sequence in terms of thermal properties, and to thermally characterize peroxide-resistant organic matter. Clay-sized fractions were isolated from a sequence of soils ranging from native forest to long-term bare fallow, and analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC) before and after hydrogen peroxide treatment. Differential scanning calorimetry traces had exothermic maxima near 285 and 333 °C, consistent with analyses of chemically extracted organic matter and humic substances reported in the literature. Peak fitting analyses showed that these maxima consisted of several hidden peaks, but their interpretation is problematic. The qualitative shifts in the thermal properties of clay-associated organic matter with differing land use observed in the DSC traces were quantified using cultivation and fallow treatment to forest ratios. Thermogravimetric mass loss ratios were greater in the thermally labile (180–310 °C) exothermic region than in the more thermally resistant (310–450 °C) exothermic region. Similarly, ratios of peak heights and areas for the fitted DSC peaks were higher for the 324 °C peak, compared to peaks at 257 and 284 °C. The higher ratios indicate that the more thermally resistant organic matter has been retained and the more thermally labile organic matter is lost. The observed shift in the distribution of organic matter from thermally labile to thermally resistant fractions from forest to long-term bare fallow clay samples is consistent with the current paradigm of decomposition consisting of a shift to more biologically resistant fractions with increasing time under cultivation and decreasing organic matter inputs. These results suggest that the thermal properties of clay-associated organic matter are related to their biological decomposability. Hydrogen peroxide treatment of clay samples removed approximately 87% of the initial organic C in all samples, and peroxide-resistant organic matter was found to be more thermally stable than the whole. However, thermal analyses of the peroxide-resistant fraction did not show any changes in thermal properties with decreases in total C content. Rather than isolating a biologically resistant pool of organic matter, peroxide-resistant organic matter may isolate an inert pool of soil organic matter with thermal properties consistent with the presence of black carbon, which remains unchanged by changes in land use.
Uridine diphospho-glucuronosyltransferases (UGTs) inactivate and facilitate the excretion of estrogens to glucuronides (-G), the most abundant circulating estrogen conjugates. The identity of the ...conjugated estrogens formed by all known overexpressed UGTs (n = 16) was analyzed by comparison with retention time and mass fragmentation of authentic standards by HPLC tandem mass spectrometry methods. Six UGTs, namely 1A1, 1A3, 1A8, 1A9, 1A10, and 2B7, were found to glucuronidate estradiol (E2) and estrone (E1), their hydroxyls (OH), and their methoxy derivatives (MeO). Addition of glucuronic acid was catalyzed by specific UGTs at positions 2, 3, and 4 of the estrogens, whereas only E2 was conjugated at position 17 by UGT2B7. Kinetic parameters indicate that the conjugation of E2 at position 3 was predominantly catalyzed by 1A1, 1A3, and 1A8 and by 1A8 for E1. Conjugation of 2-OHE1/E2 and 2- and 4-MeOE1/E2 was selective at position 3, mostly catalyzed by 1A1 and 1A8. Of all UGTs, UGT2B7 demonstrated the highest catalytic activities for estrogens and at least 10- to 50-fold higher activity for the conjugation of genotoxic 4-hydroxycatecholestrogens at position 4, compared with the conjugation of E2, E1, and 2-hydroxycatecholestrogens. Its presence was further shown in the endometrium by RT-PCR and immunohistochemistry, localizing in the same cells expressing CYP1B1, involved locally in the formation of 4-hydroxycatecholestrogens. Data show that several UGT enzymes detected in the endometrium are involved in the glucuronidation of E2 and its 2-OH, 4-OH, and 2-MeO metabolites that exert various biological effects in the tissue.
UDP-glucuronosyltransferase (UGT) 1A1 is involved in the inactivation of estradiol (E(2)) and its oxidized metabolites. These metabolites have been shown to contribute to the development of ...endometrial cancer in animal studies. Thus UGT1A1 represents a candidate gene in endometrial carcinogenesis. In this study, we established the substrate specificity of UGT1A1 for E(2) and its 2- and 4-hydroxylated metabolites. Intrinsic clearances indicated that UGT1A1 had a preference for the glucuronidation of 2-hydroxyestradiol, a metabolite associated with antiproliferative activity. Expression analysis demonstrated that UGT1A1 is present in the nonmalignant endometrium. Subsequently, we sought to determine whether the common UGT1A1 promoter allele, UGT1A1*28 A(TA)(7)TAA, which decreases gene transcription, was associated with endometrial cancer risk in a case-control study nested within the Nurses' Health Study (222 cases, 666 matched controls). Conditional logistic regression demonstrated a significant inverse association with the UGT1A1*28 allele and endometrial cancer risk. Compared with women homozygous for the UGT1A1*1 A(TA)(6)TAA allele, the adjusted odds ratio (OR) was 0.81 95% confidence interval (CI), 0.56-1.16 for the UGT1A1*1/*28 genotype and 0.40 (95% CI, 0.21-0.75) for the homozygous UGT1A1*28 genotype (P(trend) = 0.007). There was a suggestion of an interaction by menopausal status OR = 0.39 (95% CI, 0.18-0.85) for premenopausal women and OR = 0.79 (95% CI, 0.55-1.13) for postmenopausal women who carry the UGT1A1*28 allele (P(interaction) = 0.05). These observations suggest that lower expression of UGT1A1 decreases the risk of endometrial cancer by reducing the excretion of 2-hydroxyestradiol, the antiproliferative metabolite of E(2), in the endometrium.
Abstract Background Noroviruses (NoVs) are the leading cause of infectious gastroenteritis worldwide. Real-time reverse transcription PCR (real-time RT-PCR) is the preferred method of NoV detection ...for the majority of testing laboratories. Although the accepted target region for molecular detection assays is the conserved ORF1/ORF2 junction, multiple variations have been published with differences in primers, probes, reagents, multiplexing, etc. Objectives We assessed the detection limit for GII.4 NoV real-time RT-PCR assays as well as the ability to detect the non-GII.4 NoV genotypes in each participating laboratory. Study design A panel of 25 RNA samples was circulated to 18 testing laboratories for comparison of their real-time RT-PCR procedures for NoV detection. Results Multiple protocols with slight differences in reagents or conditions successfully detected 10 genome equivalents or fewer of NoV per reaction. Multiplex procedures were significantly associated ( p = 0.04) with false negative results, particularly for a GI.2 strain. Sensitive detection was associated with false positive results ( p = 0.03). Conclusions Overall, the data indicate that comparable results are produced under slightly different assay conditions.
The management of impulse control disorders (ICDs) in Parkinson's disease (PD) relies on their early identification, allowing adjustment of antiparkinsonian treatment before these manifestations lead ...to major social, financial or legal consequences. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease–Rating Scale (QUIP-RS) is an English-developed and -validated PD-specific rating scale constructed to support the rating of ICDs and related disorders and the assessment of changes in symptom severity over time, but it has not to date been validated in French.
We conducted an observational, multicenter, cross-sectional study among a subset of patients (n = 280) from the Drug Interacting with Genes in PD (DIG-PD) cohort, aiming to assess psychometric properties of the French version of QUIP-RS: acceptability, internal consistency, factor analysis, reproductibility and hypotheses testing. In addition to this scale, the following measures were applied: MDS-Unified Parkinson's Disease Rating Scale, Mini-Mental State Examination, Frontal Assessment Behavior, and Ardouin Scale of Behavior in Parkinson's Disease (ASBPD).
Cronbach's alpha coefficient was 0.72 and ranged from 0.25 to 0.55. Regarding test–retest reliability and inter-rater reliability, the Lin concordance coefficient for items was higher than 0.58. The correlations between QUIP-RS and ASBPD were moderate to high except for dopaminergic addiction and hobbyism (r = 0.41 and 0.40 respectively, p < 0.001). No clinically significant correlation was found between QUIP-RS total score (and items) and other scales.
The French version of the QUIP-RS appears to be a valid, reliable, and precise instrument for the assessment of ICDs and related disorders in PD.
clinicaltrials.gov number NCT01564992.
•Impulse control disorders can lead to major social, financial or legal consequences.•Their assessment is crucial to allow early adjustment of dopaminergic therapy.•QUIP-RS is an English validated PD-specific rating scale allowing assessment of ICDs.•French version of QUIP-RS is a valid and reliable instrument for ICDs assessment in PD.
1
The objective of the present experiments was to assess the involvement of endothelin‐A (ETA) receptors in mediating the effects of endothelin‐1 on microvascular permeability in conscious rats.
2
...Bolus injection of endothelin‐1 (0.1 and 1 nmol kg−1, i.v.) resulted in a dose‐dependent prolonged pressor effect preceded by a transient depressor response. These changes were accompanied by a dose‐dependent loss of plasma volume. Endothelin‐1 (1 nmol kg−1) enhanced the vascular permeability of the upper and lower bronchi, kidney, stomach, duodenum and spleen (up to 270%) as measured by the extravasation of Evans blue dye.
3
Pretreatment of the animals with the selective ETA receptor antagonist, BQ‐123 (1 mg kg−1, i.v.) significantly blunted the pressor response to endothelin‐1 without affecting the depressor response. BQ‐123 inhibited by 87% the endothelin‐1 (1 nmol kg−1)‐induced plasma volume loss. BQ‐123 markedly attenuated protein extravasation elicited by endothelin‐1 in the upper and lower bronchi and kidney, whereas it completely inhibited the permeability effect of endothelin‐1 in the stomach and duodenum. BQ‐123 by itself had no significant effect on the parameters studied.
4
The endothelin‐1 analogue, Trp(For)21‐endothelin‐1, in which Trp21 is formylated, was as potent a pressor agent as endothelin‐1, but had no depressor action. Bolus injection of Trp(For)21‐endothelin‐l (0.1 and 1 nmol kg−1, i.v.) evoked similar plasma volume losses to those observed following administration of equimolar doses of endothelin‐1. Furthermore, 1 nmol kg−1 Trp(For)21‐endothelin‐l evoked increases in protein extravasation similar to endothelin‐1, 1 nmol kg−1.
5
The present findings suggest that endothelin‐1 enhances microvascular permeability, in part, via the activation of ETA receptors.
PDF
