bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of Cr(VI) by soil humic acids
Authors: WITTBRODT PAUL R. , PALMER CARL D. 
Published: August 2005

SummaryThe rate of hexavalent chromium reduction by a soil humic acid (SHA) was investigated in aqueous solutions where concentrations of Cr(VI), H+, and SHA were independently varied. Rate experiments were done with a large excess of SHA over Cr(VI). Rates of reduction depend strongly on [H+], increasing with decreasing pH. Typical Cr(VI)‐SHA reactions display a nonlinear reduction of Cr(VI) with time that cannot be modelled with simple first‐ or second‐order rate equations. An empirical rate equation is developed for Cr(VI)‐soil humic acid reactions over a range of experimental conditions. The model is in part based on a reactive continuum concept developed for soil fulvic acids. The rate equation describing Cr(VI) reduction by SHA is:
R= ‐(k0+k[H+]1/2)[HCrO4−]1/2Xe−1,
where k0 is (8·3 ± 1·2) × 10−12, s−1k is (2·04 ± 0·05) × 10−9 l1/2 mol−1/2 s−1, and Xe is the equivalent fraction of SHA oxidized. The rate equation adequately models Cr(VI) reduction in an experiment with [Cr(VI)]0 four times greater than the maximum concentration used in its derivation. Cr(VI) reduction at pH 3 by two other SHAs can also be modelled using the rate equation. The difference between the rate coefficients for the humic acid and the fulvic acid from the same soil was greater than the difference in the rate coefficients for humic acids from different soils.
Fate of carbon and nitrogen in water‐stable aggregates during decomposition of 13C15N‐labelled wheat straw in situ
Authors: ANGERS D.A. , RECOUS S. , AITA C. 
Published: August 2005

SummaryWhen incorporated in soil, plant residues and their decomposition products are in close contact with mineral particles with which they can be bound to form aggregates. We measured the incorporation of carbon (C) and nitrogen (N) derived from crop residues in water‐stable aggregate fractions of a silty soil in a field experiment in Northern France using 13C15N‐labelled wheat straw (Triticum aestivum L.). Soil samples were taken seven times for 18 months and separated into slaking‐resistant aggregate size fractions which were analysed for total C and N contents, and 13C and 15N enrichments. During the early stages of decomposition (approximately 200 days), the enrichment of 13C increased rapidly in the macro aggregates (> 250 pm) but decreased thereafter. The macro aggregates represented only < 20% of the soil mass and at any one time, they accounted for <25% of the residual 13C in the soil. The proportion of 13C recovered in the <50‐μm and 50–250‐μm fractions increased during decomposition of the residues; at day 574, the 50–250‐μm fraction accounted for close to 50% of the residual 13C. A greater proportion of 15N than 13C was recovered in the <50‐μm fraction. The results indicate that during decomposition in soil, C and N from crop residues become rapidly associated with stable aggregates. In this silty soil the 50–250‐μm stable aggregates appear to be involved in the storage and stabilization of C from residues.
Inhibiting Biosynthesis and/or Metabolism of Progestins in the Ventral Tegmental Area Attenuates Lordosis of Rats in Behavioural Oestrus
Authors: Petralia S. M. , Jahagirdar V. , Frye C. A. 
Published: August 2005

AbstractIn the ventral tegmental area (VTA), lordosis of rats is facilitated by 5α‐pregnan‐3α‐ol‐20‐one (3α,5α‐THP). Central 3α,5α‐THP results from metabolism of peripheral progesterone, from the ovaries and/or adrenals, by sequential enzymatic activity of 5α‐reductase and 3α‐hydroxysteroid oxidoreductase (3α‐HSOR). In addition, in glial cells, cholesterol is converted into pregnenolone by the P450 side‐chain cleavage enzyme (P450scc), which is then metabolized to progesterone by 3β‐hydroxysteroid dehydrogenase, and subsequently reduced to 3α,5α‐THP. We hypothesize that, in the VTA, formation of 3α,5α‐THP by both metabolism and biosynthesis is necessary for facilitation of lordosis of female rats. In Experiment 1, naturally‐receptive rats received bilateral VTA infusions of a P450scc inhibitor, digitoxin (1 µg/side); a 5α‐reductase inhibitor, finasteride (10 µg/side); digitoxin (1 µg/side) + finasteride (10 µg/side); or vehicle and were tested 3 h later for lordosis. In Experiment 2, the effects of VTA infusions of digitoxin, finasteride, digitoxin + finasteride, or vehicle on lordosis and midbrain and plasma 3α,5α‐THP levels were examined. In Experiment 3, we investigated whether infusions of 3α,5α‐THP to the VTA reinstated lordosis and midbrain 3α,5α‐THP levels following administration of inhibitors. VTA infusions of digitoxin, finasteride, or digitoxin + finasteride, significantly and similarly reduced lordosis and midbrain, but not plasma 3α,5α‐THP levels, compared to vehicle. Following receipt of inhibitor infusions, 3α,5α‐THP to the VTA restored lordosis and midbrain 3α,5α‐THP levels. These data suggest that, in the VTA, both central biosynthesis of progesterone and metabolism of progesterone (from central and/or peripheral sources) to 3α,5α‐THP are important for mediating lordosis of rats.
Interactions Between Kinases and Phosphatases in the Rapid Control of Brain Aromatase
Authors: Balthazart J. , Baillien M. , Ball G. F. 
Published: August 2005

AbstractAromatization of testosterone into oestradiol plays a key role in the activation of male sexual behaviour in many vertebrate species. Rapid changes in brain aromatase activity have recently been identified and the resulting changes in local oestrogen bioavailability could modulate fast behavioural responses to oestrogens. In quail hypothalamic homogenates, aromatase activity is down‐regulated within minutes by calcium‐dependent phosphorylations in the presence of ATP, MgCl2 and CaCl2 (ATP/Mg/Ca). Three kinases (protein kinases A and C and calmodulin kinase; PKA, PKC and CAMK) are potentially implicated in this process. If kinases decrease aromatase activity in a reversible manner, then it would be expected that the enzymatic activity would increase and/or return to baseline levels in the presence of phosphatases. We showed previously that 0.1 mM vanadate (a general inhibitor of protein phosphatases) significantly decreases aromatase activity but specific protein phosphatases that could up‐regulate aromatase activity have not been identified to date. The reversibility of aromatase activity inhibition by phosphorylations was investigated in the present study using alkaline and acid phosphatase (Alk and Ac PPase). Unexpectedly, Alk PPase inhibited aromatase activity in a dose‐dependent manner in the presence, as well as in the absence, of ATP/Mg/Ca. By contrast, Ac PPase completely blocked the inhibitory effects of ATP/Mg/Ca on aromatase activity, even if it moderately inhibited aromatase activity in the absence of ATP/Mg/Ca. However, the addition of Ac PPase was unable to restore aromatase activity after it had been inhibited by exposure to ATP/Mg/Ca. Taken together, these data suggest that, amongst the 15 potential consensus phosphorylation sites identified on the quail aromatase sequence, some must be constitutively phosphorylated for the enzyme to be active whereas phosphorylation of the others is involved in the rapid inhibition of aromatase activity by the competitive effects of protein kinases and phosphatases. Two out of these 15 putative phosphorylation sites occur in an environment corresponding to the consensus sites for PKC, PKA (and possibly a CAMK) and, in all probability, represent the sites whose phosphorylation rapidly blocks enzyme activity.
Developmental Changes in GABAA Receptor Subunit Composition Within the Gonadotrophin‐Releasing Hormone‐1 Neuronal System
Authors: Temple J. L. , Wray S. 
Published: August 2005

AbstractIt is becoming increasingly evident that GABA plays an important role in the regulation of gonadotrophin‐releasing hormone (GnRH)‐1 neurones via the GABAA receptor. The aim of the present study was to characterise expression of the GABAA receptor within the GnRH‐1 system across development. The expression pattern of five GABAAα subunits and one GABAAβ subunit was first examined within individual GnRH‐1 neurones by the polymerase chain reaction. A significant increase in the expression of GABAAα2 and a significant decrease in the expression of GABAAα6 over time were found. Of the other subunits examined, two (α1 and α3) showed no differences in expression and two (α4 and β3) showed variable low incidence of expression. Given the reciprocal relationship of α2 and α6 expression, we hypothesised that there is a developmental switch in the expression of these subunits in GnRH‐1 neurones. To investigate this hypothesis, single‐ and double‐label immunocytochemistry for GABAAα2 and α6 and GnRH‐1 was performed in tissue from ages E12.5 to adulthood, as well as in nasal explants. We show that GABAAα2 and α6 are present in the GnRH‐1 neuronal system both in vivo and in vitro and that the levels of expression are altered as a function of age.
Chronic Prenatal Ethanol Exposure Alters Glucocorticoid Signalling in the Hippocampus of the Postnatal Guinea Pig
Authors: Iqbal U. , Brien J. F. , Banjanin S. , Andrews M. H. , Matthews S. G. , Reynolds J. N. 
Published: August 2005

AbstractThe present study tested the hypothesis that chronic prenatal ethanol exposure causes long‐lasting changes in glucocorticoid signalling in postnatal offspring. Pregnant guinea pigs were treated with ethanol (4 g/kg maternal body weight/day), isocaloric‐sucrose/pair‐feeding or water throughout gestation, and maternal saliva cortisol concentration was determined 2 h after treatment at different stages of gestation. Electrically‐stimulated release of glutamate and GABA, in the presence or absence of dexamethasone, as well as glucocorticoid and mineralocorticoid receptor mRNA expression, was determined in the hippocampus and prefrontal cortex of adult offspring of treated pregnant guinea pigs. Maternal saliva cortisol concentration increased throughout pregnancy, which was associated with increased foetal plasma and amniotic fluid cortisol concentration. Ethanol administration to pregnant guinea pigs increased maternal saliva cortisol concentration during early and mid‐gestation. In late gestation, ethanol administration did not increase saliva cortisol concentration above that induced by pregnancy. Chronic prenatal ethanol exposure had no effect on stimulated glutamate or GABA release, but selectively prevented dexamethasone‐mediated suppression of stimulated glutamate release, and decreased expression of mineralocorticoid, but not glucocorticoid, receptor mRNA in the hippocampus of adult offspring. These data indicate that maternal ethanol administration leads to excessively increased maternal cortisol concentration that can impact negatively the developing foetal brain, leading to persistent postnatal deficits in glucocorticoid regulation of glutamate signalling in the adult hippocampus.
Leukemia‐Derived Dendritic Cells can be Generated from Blood or Bone Marrow Cells from Patients with Acute Myeloid Leukaemia: A Methodological Approach under Serum‐Free Culture Conditions
Authors: Kufner S. , Zitzelsberger H. , Kroell T. , Pelka‐Fleischer R. , Salem A. , De Valle F. , Schweiger C. , Nuessler V. , Schmid C. , Kolb H. J. , Schmetzer H. M. 
Published: August 2005

AbstractFunctional dendritic cells (DC) are professional antigen‐presenting cells (APC) and can be generated in vitro from healthy as well as from leukaemic cells from acute myeloid leukemia (AML) patients giving rise to APC of leukaemic origin‐presenting leukaemic antigens. We describe the generation and characterization of DC from different mononuclear cell (MNC) fractions from 50 AML patients under different serum‐free culture conditions, determine the optimal culture conditions and compare the results with that from 23 healthy donors. In parallel cultures, we compared DC harvests after 7‐ or 14‐day culture, with total or adherent MNC or T‐cell depleted MNC or peripheral blood (PB) or bone marrow‐MNC (BM–MNC), thawn or fresh MNC, in Xvivo or CellGro serum‐free media, ±10% autologous plasma or ±FL. In detail, we could show that AML–DC harvests were higher after 10–14 days culture (healthy DC: 7 days); total or adherent PB or BM–MNC fractions yield comparable DC counts, however, from magnetic cell sorting (MACS)‐depleted MNC fractions or thawn MNC lower DC counts can be generated. Whereas the addition of FL increases the DC harvest, the addition of autologous plasma in many cases has inhibitory influence on DC maturation. CellGro and Xvivo media yield comparable DC counts. Optimal harvest of vital and mature DC from AML samples was obtained with a granulocyte/macrophage‐colony stimulating factor, interleukin‐4, FL and tumour necrosis factor‐α‐containing serum‐free Xvivo medium after 10–14 days of culture (36/26% DC; 38/64% vital DC; 46/51% mature DC were generated from AML/healthy MNC samples). Surface marker profiles (e.g. costimulatory antigen expressing) of DC obtained from AML samples were comparable with that of healthy DC. The leukaemic derivation of AML–DC was demonstrated by the persistence of the clonal cytogenetic aberration in the DC or by coexpression of leukaemic antigens on DC. Autologous T‐cell activation of leukaemia‐derived DC was demonstrated in cases with AML. Autologous T cells proliferate and upregulate DC‐contact‐relevant antigens. We demonstrate that the generation of leukaemia‐derived DC is feasable in AML under serum‐free culture conditions giving rise to DC with comparable characteristics as healthy DC and offering an anti‐leukaemia‐directed immunotherapeutical vaccination strategy in AML.
The Six Mammalian Cell Entry Proteins (Mce3A–F) Encoded by the mce3 Operon are Expressed During In Vitro Growth of Mycobacterium tuberculosis
Authors: Ahmad S. , El‐Shazly S. , Mustafa A. S. , Al‐Attiyah R. 
Published: August 2005

AbstractThe pathogenesis of Mycobacterium tuberculosis is largely due to its ability to enter and survive within human macrophages. The mammalian cell entry (mce)3 operon is one of four homologous mce operons that encodes six putative invasin‐like exported proteins (Mce3A–F), possibly involved in entry and survival of M. tuberculosis inside macrophages. We have recently shown that Mce3A, Mce3D and Mce3E are expressed and elicit antibody responses in a majority of human subjects during natural infection with M. tuberculosis. In this study, we demonstrate the expression of Mce3A–F proteins and their mRNA during in vitro growth of M. tuberculosis. To demonstrate the expression of mce3A–F proteins, the antibodies were raised in rabbits against three pure proteins (Mce3A, Mce3D and Mce3E), and their specificity was checked by immunoblotting with recombinant Mce1A–F proteins encoded by mce1 operon. The antibodies were also generated against all the six Mce3 proteins, which were expressed and purified as fusion proteins with glutathione S‐transferase (GST) as the fusion partner (GST‐Mce3A–F). The antibodies reacted, in each case, with a protein of expected molecular mass (Mr) for the corresponding Mce3 protein in the cell wall fraction but not in the soluble fraction of in vitro‐grown M. tuberculosis cells. The presence of mRNA for mce3A–F genes was also shown by using mce3A–F gene‐specific primers, and total RNA isolated from in vitro‐grown M. tuberculosis cells by reverse transcription‐polymerase chain reaction (RT‐PCR). Pretreatment of the RNA preparation with RNase A abolished amplification in RT‐PCR confirming that mce3A–F mRNA rather than genomic DNA was being amplified. The data show that Mce3A–F encoded by the mce3 operon are expressed during in vitro growth of M. tuberculosis.
Reactivation of Antigen‐Induced Arthritis in Mice by Oral Administration of Lipopolysaccharide
Authors: Yoshino S. , Yamaki K. , Taneda S. , Yanagisawa R. , Takano H. 
Published: August 2005

AbstractWe examined whether oral administration of lipopolysaccharide (LPS) from Escherichia coli reactivated antigen‐induced arthritis (AIA) in mice that is one of models of human rheumatoid arthritis. To induce AIA, mice were immunized by subcutaneous injection of ovalbumin (OVA) emulsified with complete Freund's adjuvant into the base of the tail (day 0) followed by intraarticular injection of OVA on day 21. To investigate the ability of LPS to reactivate AIA, varying doses of LPS were p.o. administered 48 h after the challenge injection. The results showed that administration of LPS was followed by reactivation of AIA in a dose‐related fashion. The reactivation of AIA by LPS was associated with increases in interferon‐γ, interleukin‐1β and tumour necrosis factor‐α. Polymyxin B sulfate given immediately before administration of LPS suppressed the reactivation of AIA. These findings suggest that LPS from intestinal bacteria may play a role in the reactivation of joint inflammation in which immune responses to pathogenic antigens are involved.
The Immunostimulatory Peptide WKYMVm‐NH2 Activates Bone Marrow Mouse Neutrophils via Multiple Signal Transduction Pathways
Authors: Boxio R. , Bossenmeyer‐Pourié C. , Vanderesse R. , Dournon C. , Nüße O. 
Published: August 2005

AbstractG‐protein‐coupled receptors play a major role in the activation of the innate immune system, such as polymorphonuclear neutrophils. Members of the formyl peptide receptor family recognize chemotactic peptides as well the amyloïd‐β peptide and fragments of the human immunodeficiency virus envelope and may thus be implicated in major pathologies. The peptide WKYMVm‐NH2 probably activates the receptor FPRL1 and its mouse orthologues Fpr‐rs1 and Fpr‐rs2. We examined the stimulation of C57BL6 mouse neutrophils by WKYMVm‐NH2 and the effects of several inhibitors for intracellular signalling pathways (wortmannin, LY 294002, staurosporin, H‐89, U 73122, thapsigargin and SKF 96365). We show here that WKYMVm‐NH2 is a powerful stimulator of primary and secondary granule exocytosis as well as superoxide production. The signalling pathway involves phosphoinositide 3‐kinase, protein kinase C, phospholipase C and store‐operated calcium influx. Studies with peptide antagonists suggest that WKYMVm‐NH2 preferentially activates exocytosis via FPRL1 and not FPR, the major receptor for N‐formylated peptides such as fMLF. However, the signalling pathways activated by WKYMVm‐NH2 in mouse neutrophils are similar to those activated by fMLF in human neutrophils. Thus, the effect and the signalling pathways of the two agonists and their receptors are at least partially overlapping.
Cytokine Responses to Fungal Pathogens in Kupffer Cells are Toll‐like Receptor 4 Independent and Mediated by Tyrosine Kinases
Authors: Øverland G. , Stuestøl J. F. , Dahle M. K. , Myhre A. E. , Netea M. G. , Verweij P. , Yndestad A. , Aukrust P. , Kullberg B. J. , Warris A. , Wang J. E. , Aasen A. O. 
Published: August 2005

AbstractDisseminated fungal infections are increasing. However, the interactions between the body's largest population of tissue macrophages, the Kupffer cells and the fungal pathogens are scarcely understood. The aim of this study was to examine the involvement of Toll‐like receptor 4 (TLR4) signalling in cytokine production, using primary cultures of rat and murine Kupffer cells exposed to Aspergillus fumigatus and Candida albicans hyphae and conidia. All fungal components induced the release of tumour necrosis factor‐α (TNF‐α), but with delayed kinetics compared with lipopolysaccharide (LPS). Candida albicans was the most potent inducer of TNF‐α protein and mRNA and the only inducer of interleukin‐10 (IL‐10) in rat Kupffer cells. All fungal components induced enhanced mRNA levels of macrophage inhibitory protein‐2 (MIP‐2) in the cells, similar to LPS. Inhibitors of Src tyrosine kinases added to cells prior to stimulation led to attenuation in the release of both TNF‐α (60%, P < 0.05) and IL‐10 (70%, P < 0.05) induced by C. albicans conidia but did not influence the LPS‐mediated cytokine release. Murine Kupffer cells (C57BL/10J) also released TNF‐α as well as the chemokines keratinocyte‐derived chemokine (KC) and MIP‐2 in response to fungal component. Surprisingly, Kupffer cells from TLR4‐deficient C57BL/ScCr mice exhibited significantly enhanced production of KC and MIP‐2 upon stimulation by fungal components compared with control littermates (P < 0.05). Our study demonstrates that Aspergillus and Candida components induce cytokine production in rat Kupffer cells and that the response to C. albicans conidia involves Src tyrosine kinases. The experiments with TLR4‐deficient Kupffer cells suggest that the cytokine response in these cells to fungal component is not mediated by TLR4.
Influence of genetic background on transformation and expression of Green Fluorescent Protein in Actinobacillus actinomycetemcomitans
Authors: Teughels W. , Sliepen I. , De Keersmaecker S. , Quirynen M. , Lippmann J. , Pauwels M. , Fives‐Taylor P. 
Published: August 2005

Background/aims:  The development of an electro‐transformation system and the construction of shuttle plasmids for Actinobacillus actinomycetemcomitans have enhanced the molecular analysis of virulence factors. However, inefficient transformation is frequently encountered. This study investigated the efficiency of electro‐transformation and expression of Green Fluorescent Protein (GFP) in 12 different A. actinomycetemcomitans strains. The influence of the plasmid vector, serotype, and phenotype were the major factors taken into consideration.Material and methods:  Twelve serotyped A. actinomycetemcomitans strains were independently electro‐transformed with two different Escherichia coli–A. actinomycetemcomitans shuttle plasmids (pVT1303 and pVT1304), both containing an identical ltx‐GFPmut2 gene construct but a different backbone (pDMG4 and pPK1, respectively). The transformation efficiency, transformation frequency, and electro‐transformation survival rate were determined by culture techniques. GFP expression was observed at the colony level by fluorescence microscopy.Results:  All strains could be transformed with both plasmids. However, major differences were observed for the transformation efficiency, transformation frequency, and electro‐transformation survival rate between strains. The data demonstrated that plasmid vector, serotype, and phenotype are key players for obtaining a successful transformation. An inverted relationship between the electro‐transformation survival rate and tranformation frequency was also observed. GFP expression was also influenced by phenotype, serotype and plasmid vector.Conclusions:  The serotype of A. actinomycetemcomitans has an important influence on its survival after electro‐transformation and on transformation frequency. The expression of GFP is strain and plasmid vector dependent.