Real-time monitoring of aqueous Hg reduction dynamics by magnetite/iron metal composite powders synthesized hydrothermally.

An iron-based powder material composed of zerovalent iron (8 wt.%) and magnetite (92 wt.%), has been synthesized hydrothermally at 200 °C from zero-valent iron.

Chemical Forms of Mercury in Human Hair Reveal Sources of Exposure.

Humans are contaminated by mercury in different forms from different sources. In practice, contamination by methylmercury from fish consumption is assessed by measuring hair mercury concentration, whereas exposure to elemental and inorganic mercury from other sources is tested by analysis of blood or urine. Here, we show that diverse sources of hair mercury at concentrations as low as 0.

Structure, Bonding, and Stability of Mercury Complexes with Thiolate and Thioether Ligands from High-Resolution XANES Spectroscopy and First-Principles Calculations.

We present results obtained from high energy-resolution L3-edge XANES spectroscopy and first-principles calculations for the structure, bonding, and stability of mercury(II) complexes with thiolate and thioether ligands in crystalline compounds, aqueous solution, and macromolecular natural organic matter (NOM). Core-to-valence XANES features that vary in intensity differentiate with unprecedented sensitivity the number and identity of Hg ligands and the geometry of the ligand environment. Post-Hartree-Fock XANES calculations, coupled with natural population analysis, performed on MP2-optimized Hg[(SR)2···(RSR)n] complexes show that the shape, position, and number of electronic transitions observed at high energy-resolution are directly correlated to the Hg and S (l,m)-projected empty densities of states and occupations of the hybridized Hg 6s and 5d valence orbitals.

Formation of Mercury Sulfide from Hg(II)-Thiolate Complexes in Natural Organic Matter.

Methylmercury is the environmental form of neurotoxic mercury that is biomagnified in the food chain. Methylation rates are reduced when the metal is sequestered in crystalline mercury sulfides or bound to thiol groups in macromolecular natural organic matter. Mercury sulfide minerals are known to nucleate in anoxic zones, by reaction of the thiol-bound mercury with biogenic sulfide, but not in oxic environments.

Solid-state transformation of nanocrystalline phyllomanganate into tectomanganate: influence of initial layer and interlayer structure.

In surficial environments, the fate of many elements is influenced by their interactions with the phyllomanganate vernadite, a nano-sized and turbostratic variety of birnessite. To advance our understanding of the surface reactivity of vernadite as a function of pH, synthetic vernadite (δ-MnO2) was equilibrated at pH ranging from 3 to 10 and characterized structurally using chemical methods, thermogravimetry and modelling of powder X-ray diffraction (XRD) patterns. With decreasing pH, the number of vacant layer sites increases in the octahedral layers of δ-MnO2 (from 0.

Thlaspi arvense binds Cu(II) as a bis-(L-histidinato) complex on root cell walls in an urban ecosystem.

Root cell walls accumulate metal cations both during acquisition from the environment and removal from the protoplast to avoid toxicity, but molecular forms of the metals under field conditions remain elusive. We have identified how copper is bound to cell walls of intact roots of native Thlaspi arvense by combining synchrotron X-ray fluorescence and absorption techniques (XANES and EXAFS) at the nano-, micro-, and bulk scales. The plants grew naturally in sediment in a stormwater runoff basin at copper concentrations typical of urban ecosystems.

Natural attenuation of zinc pollution in smelter-affected soil.

Previous synchrotron X-ray microprobe measurements of Zn speciation in contaminated and uncontaminated soils have identified phyllosilicate as the main sequestration phase. The emphasis now is focused on comparing the nature and properties of neoformed and geogenic phyllosilicate species to understand natural attenuation processes. Refined structural characterization of the two types of Zn-containing phyllosilicate in slightly basic smelter-affected agricultural soils were obtained using a so far unprecedented combination of X-ray microscopic techniques, including fluorescence (μ-XRF), absorption (μ-EXAFS), and diffraction (μ-XRD), and X-ray bulk-sensitive techniques, including powder and polarized EXAFS spectroscopy.

Formation of metallic copper nanoparticles at the soil-root interface.

Copper is an essential element in the cellular electron-transport chain, but as a free ion it can catalyze production of damaging radicals. Thus, all life forms attempt to prevent copper toxicity. Plants diminish excess copper in two structural regions: rare hyperaccumulators bind cationic copper to organic ligands in subaerial tissues, whereas widespread metal-tolerant plants segregate copper dominantly in roots by mechanisms thought to be analogous.

Na+/H+ exchange inhibition with cariporide prevents alterations of coronary endothelial function in streptozotocin-induced diabetes.

Hyperglycemia encountered during diabetes triggers abnormalities of vascular function associated with cell acidosis and calcium overload. The purpose of this study was to determine, whether Na+/H+ exchanger (NHE-1) inhibition by cariporide protects coronary cells against the deleterious effect of hyperglycemia in the rat. In vivo hyperglycemia was triggered by streptozotocin injection.

Supplementation of MCF-7 cells with essential fatty acids induces the activation of protein kinase C in response to IGF-1.

The effects of changing the composition of membrane lipids on protein kinase C (PKC) activation were studied in MCF-7 human breast cancer cells. The supply of linoleate or alpha-linolenate to MCF-7 cells altered cell membranes fatty acid composition but did not affect PKC activity. When the cells were additionally exposed to IGF-1, the same fatty acids caused a dramatic increase in membrane-bound PKC activity.

Membrane fatty acids of breast carcinoma: contribution of host fatty acids and tumor properties.

To assess the part that host fatty-acid supply and tumor-specific fatty-acid utilization contribute to the membrane lipid composition of tumor tissue, intra-individual comparisons of membrane fatty acids were carried out between breast-carcinoma tissue and non-tumorous breast tissue adjacent to the tumor and taken as reference. Phospholipids were purified by thin-layer chromatography from tumor biopsies obtained from 59 patients with a localized presentation of breast cancer, and fatty acids analyzed by capillary gas chromatography. Elevated levels of palmitic, palmitoleic and arachidonic acids, along with a low level of linoleic acid, were observed in membrane phospholipids of tumors with poor histoprognostic grade.

Analysis of the lipid content and the motility of human sperm after follicular fluid treatment.

The effect of human follicular fluid (hFF) on the cholesterol and phospholipid content and the movement characteristics of human spermatozoa were studied. Semen was selected by a discontinuous Percoll gradient and incubated during in vitro capacitating conditions with B2 medium supplemented with hFF 20%. Percoll pelleted spermatozoa were incubated in either B2 (B2-Percoll) or B2 supplemented with hFF (hFF-Percoll).

[Follicular fluid: role and importance in the preparation of spermatozoa for fertilization].

It has been demonstrated that the preovulatory follicular fluid creates a micro-environment which is of importance for normal sperm function. In this paper, we attempt to evaluate the role of human follicular fluid (HFF) on the fertilizing capacity of spermatozoa.

Triacylglycerol structure of human colostrum and mature milk.

Because triacylglycerol (TAG) structure influences the metabolic fate of its component fatty acids, we have examined human colostrum and mature milk TAG with particular attention to the location of the very long chain polyunsaturated fatty acid on the glycerol backbone. The analysis was based on the formation of various diacylglycerol species from human milk TAG upon chemical (Grignard degradation) or enzymatic degradation. The structure of the TAG was subsequently deduced from data obtained by gas chromatographic analysis of the fatty acid methyl esters in the diacylglycerol subfractions.

Treatment of human spermatozoa with follicular fluid can influence lipid content and motility during in vitro capacitation.

In order to evaluate the role of human follicular fluid (HFF) on the fertilizing capacity of spermatozoa, we studied the effect of HFF on the lipid composition and on the movement characteristics of human spermatozoa. Spermatozoa (spz) from normospermic patients were prepared with a discontinuous Percoll gradient and incubated in Ménézo B2 medium with or without a supplement of 20% HFF (HFF-Percoll spz and B2-Percoll spz respectively) for 2 and 24 h. After 2 h HFF incubation, percentage progressive motility, straight line velocity (VSL), and amplitude of lateral head displacement (ALH) were improved in HFF-Percoll spz as compared to B2-Percoll spz (P < or = 0.

A cross-linking assay allows the detection of receptors for the somatostatin analogue, lanreotide in human breast tumours.

Hypothalamic somatostatin and its synthetic analogues inhibit the cell growth of several tumour models. The somatostatin analogue lanreotide (somatuline or BIM23014C) inhibits both the in vivo and in vitro cell growth of various mammary tumours. In order to evaluate the presence of receptors for lanreotide in breast tissue, samples from 41 female and 2 male patients were analysed by a cross-linking assay.

Prognostic significance of tumor phosphatidylcholine stearic acid level in breast carcinoma.

The involvement of lipid enzymes in the action of oncogenes at the cell membrane level has suggested that membrane lipids could play a role in modulating the growth of tumors. We previously found that breast cancer patients with a low level of polyunsaturated fatty acids in their primary tumor's phosphatidylethanolamine had a high risk of early occurrence of visceral metastasis. In the present study, we prospectively examined whether fatty acid composition of tumor membrane phosphatidylcholine had a prognostic significance in a series of 63 patients with a localized presentation of breast cancer.

Molecular heterogeneity of somatostatin analogue BIM-23014C receptors in human breast carcinoma cells using the chemical cross-linking assay.

Distinct proteins complexed with somatostatin and the somatostatin analogue BIM-23014C were revealed in human breast cancer cells using the cross-linking assay. One BIM-23014C-specific complex (Mr 57,000) was observed in MCF-7 (monolayer, nodule, and tumor) and T47D. Growth inhibition of MCF-7 tumor xenografts by BIM-23014C was dose related in the 6-day subrenal capsule assay.

Fatty-acid composition of breast and iliac adipose tissue in breast-cancer patients.

In order to determine to what extent the fatty-acid composition of breast adipose tissue is representative of the body-fat composition in breast carcinoma, we compared the fatty-acid composition of breast adipose tissue to that of iliac fat in breast-cancer patients. Triglycerides from the 2 sites were purified by thin-layer chromatography and fatty-acid composition was determined by capillary gas chromatography. Compared with iliac fat, mammary fat was higher in saturated (33.

Essential fatty acid composition of human colostrum triglycerides: its relationship with adipose tissue composition.

The relationships between essential fatty acid (EFA) composition of colostrum and white adipose tissue (WAT) were examined on day 5 after delivery in 69 healthy women. Fatty acid composition was assessed by capillary gas chromatography, and 33 fatty acids were detected in colostrum and in WAT. Total polyunsaturated fatty acid (PUFA) content was similar in colostrum and in WAT (15.

Conformational variations in d(TGACGTCA) and its reverse sequence d(ACTGCAGT): a joint circular dichroism and nuclear magnetic resonance study.

Circular dichroism (CD) and nuclear magnetic resonance (NMR) techniques have been used to characterize the structural properties of the two self-complementary DNA octamers d(TGACGTCA) (I) and d(ACTGCAGT) (II). These display as distinctive features reverse sequences and central steps CpG and GpC, respectively. CD experiments lead to B-form DNA spectra characterized by larger magnitude signals in the case of octamer (I).

Presence of PAF-acether in human breast carcinoma: relation to axillary lymph node metastasis.

PAF-acether (PAF; formerly platelet-activating factor), a potent lipid mediator of inflammation, is involved in multiple cellular functions. To evaluate the role of PAF in human cancer, we obtained specimens from patients with localized breast carcinoma and assayed them for PAF. PAF was found in almost all carcinoma, although it was not detected in most of the matched, nontumor breast tissue samples.

Chemical characterization and functional role of human glomerular basement membrane components.

Subfractions of human glomerular basement membrane isolated by enzymatic procedures were analyzed for their chemical structure and biological activity. Pepsin or collagenase digestion of purified basement membranes released three groups of components: collagenous and noncollagenous fractions and also a mixed material consisting of a proteolysis-resistant association between collagen sequences and heteropolysaccharidic glycopeptides. These different fractions were explored in vitro for their ability to interact with cell membranes.