On the use of X-ray absorption spectroscopy to elucidate the structure of lutetium adenosine mono- and triphosphate complexes.

Although the physiological impact of the actinide elements as nuclear toxicants has been widely investigated for half a century, a description of their interactions with biological molecules remains limited. It is however of primary importance to better assess the determinants of actinide speciation in cells and more generally in living organisms to unravel the molecular processes underlying actinide transport and deposition in tissues. The biological pathways of this family of elements in case of accidental contamination or chronic natural exposure (in the case of uranium rich soils for instance) are therefore a crucial issue of public health and of societal impact. Because of the high chemical affinity of those actinide elements for phosphate groups and the ubiquity of such chemical functions in biochemistry, phosphate derivatives are considered as probable targets of these cations. Among them, nucleotides and in particular adenosine mono- (AMP) and triphosphate (ATP) nucleotides occur in more chemical reactions than any other compounds on the earth's surface, except water, and are therefore critical target molecules. In the present study, we are interested in trans-plutonium actinide elements, in particular americium and curium that are more rarely considered in environmental and bioaccumulation studies than early actinides like uranium, neptunium and plutonium. A first step in this strategy is to work with chemical analogues like lanthanides that are not radioactive and therefore allow extended physical chemical characterization to be conducted that are difficult to perform with radioactive materials. We describe herein the interaction of lutetium(III) with adenosine AMP and ATP. With AMP and ATP, insoluble amorphous compounds have been obtained with molar ratios of 1:2 and 1:1, respectively. With an excess of ATP, with 1:2 molar ratio, a soluble complex has been obtained. A combination of spectroscopic techniques (IR, NMR, ESI-MS, EXAFS) together with quantum chemical calculations has been implemented in order to assess the lutetium coordination arrangement for the two nucleotides. In all the complexes described in the article, the lutetium cation is coordinated by the phosphate groups of the nucleotide plus additional putative water molecules with various tridimensional arrangements. With AMP 1:2 and ATP 1:1 solid-state compounds, polynuclear complexes are assumed to be obtained. In contrast, with ATP 1:2 soluble compound, the Lu coordination sphere is saturated by two ATP ligands, and this favors the formation of a mononuclear complex. In order to further interpret the EXAFS data obtained at the Lu LIII edge, model structures have been calculated for the 1:1 and 1:2 ATP complexes. They are discussed and compared to the EXAFS best fit metrical parameters.

Behavior of heptavalent technetium in sulfuric acid under α-irradiation: structural determination of technetium sulfate complexes by X-ray absorption spectroscopy and first principles calculations.

The effect of α-radiolysis on the behavior of heptavalent technetium has been investigated in 13 and 18 M H2SO4. Irradiation experiments were performed using α-particles ((4)He(2+), E = 68 MeV) generated by the ARRONAX cyclotron. UV-visible and X-ray absorption fine structure spectroscopic studies indicate that Tc(VII) is reduced to Tc(V) under α-irradiation. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements are consistent with the presence of mononuclear technetium sulfate complexes. Experimental results and density functional calculations show the formation of [TcO(HSO4)3(H2O)(OH)](-) and/or [TcO(HSO4)3(H2O)2] and [Tc(HSO4)3(SO4)(H2O)] and/or [Tc(HSO4)3(SO4)(OH)](-) for 13 and 18 M H2SO4, respectively.

Clonidine effects on protein and carbohydrate electrophysiological responses of labellar and tarsal sensilla in Phormia regina.

The electrophysiological response of labellar and tarsal chemosensilla in the blowfly Phormia regina was studied in response to a complex stimulus naturally encountered by flies such as sheep faeces, and to beef liver, a proteinaceous feeding source. Responses were investigated both before or after injection of clonidine, an octopamine agonist previously shown to enhance sucrose ingestion, while decreasing that of proteins. As assessed by single sensillum recordings, the four different chemosensory - "salt", "sugar", "deterrent" and "water" - cells were all activated by both stimuli, regardless of sex and sensillum type, the "sugar" one being in all cases the most sensitive to beef liver before clonidine injection. Clonidine treatment affected neither labellar nor tarsal sensitivity to sucrose. Conversely, clonidine-injected flies showed a significant increase in the activity of the "deterrent" cell to beef liver, thus accounting for a decrease in protein ingestion. This study for the first time provides evidence of a key role of a clonidine-sensitive peripheral taste sensitivity in down-regulation of protein ingestion in blowflies. Correlation between peripheral sensitivity and behavioural output is discussed.

Effects of avermectins on olfactory responses of Culicoides imicola (Diptera: Ceratopogonidae).

The aim of this study was to examine the role of the olfactory system of the midge Culicoides imicola Kieffer as the major system mediating repellency to antihelminthic avermectins. Incidental observations indicate that treatment with Dectomax or Ivomec (commercial formula of the avermectins doramectin and ivermectin, respectively) protects sheep from infection by bluetongue (BT) viruses. Our electrophysiological data from midge antennae showed that the stimulating effectiveness of L- (+)-lactic acid, butanone, and sheep fleece odor decreased after addition of avermectins. The results show that these antihelminthics affect the olfactory sensitivity of the insect toward the animal host by reducing the response to those compounds that attract the insect, consequently reducing the possibility of biting the sheep and thereby transferring the BT virus.

New insight into the ternary complexes of uranyl carbonate in seawater.

Uranium is naturally present in seawater at trace levels and may in some cases be present at higher concentrations, due to anthropogenic nuclear activities. Understanding uranium speciation in seawater is thus essential for predicting and controlling its behavior in this specific environmental compartment and consequently, its possible impact on living organisms. The carbonato calcic complex Ca2UO2(CO3)3 was previously identified as the main uranium species in natural seawater, together with CaUO2(CO3)32-. In this work, we further investigate the role of the alkaline earth cation in the structure of the ternary uranyl-carbonate complexes. For this purpose, artificial seawater, free of Mg2+ and Ca2+, using Sr2+ as a spectroscopic probe was prepared. Combining TRLIF and EXAFS spectroscopy, together with DFT and theoretical thermodynamic calculations, evidence for the presence of Sr alkaline earth counter ion in the complex structure can be asserted. Furthermore, data suggest that when Ca2+ is replaced by Sr2+, SrUO2(CO3)32- is the main complex in solution and it occurs with the presence of at least one monodentate carbonate in the uranyl coordination sphere.

EXAFS and XANES investigation of the ETS-10 microporous titanosilicate.

In this work, we report state-of-the-art analysis of both Ti K-edge high-resolution XANES and EXAFS data collected on the ETS-10 molecular sieve at the GILDA BM8 beamline of the ESRF facility. The interatomic distances and the angles obtained in our EXAFS study are in fair agreement with the single-crystal XRD data of Wang and Jacobson (Chem. Commun. 1999, 973) and with the recent ab initio periodic study of Damin et al. (J. Phys. Chem. B 2004, 108, 1328) Differently from previous EXAFS work (J. Phys. Chem. 1996, 100, 449), our study supports a model of ETS-10 where the Ti atoms are bonded with two equivalent axial oxygen atoms. This model is also able to reproduce the edge and the post-edge region of the XANES spectrum. Conversely, the weak but well-defined pre-edge peak at 4971.3 eV can be explained only by assuming that a fraction of Ti atoms are in a local geometry similar to that of the pentacoordinated Ti sites in the ETS-4 structure. These Ti atoms in ETS-10 should be the terminal of the -Ti-O-Ti-O-Ti- chains, of which the actual number is strongly increased by the high crystal defectivity (Ti vacancies).

Bitter taste recognition in the blowfly: Electrophysiological and behavioral evidence.

Blowflies respond to sugars, salts, and water through the activation of specific chemoreceptor neurons in the labellar taste chemosensilla. These insects also detect deterrent stimuli, but identification of a specific "deterrent" chemoreceptor within their sensilla has been elusive. Here electrophysiological evidence is provided that the so-called "fifth" cell in taste chemosensilla of blowflies responds to deterrent compounds, such as quinine, amiloride, nicotine, and caffeine, which are also known to be bitter tasting for vertebrates. Therefore, comparison of behavioral and electrophysiological data, including crossadaptation analysis, suggests that the blowfly can detect "bitter" stimuli by activation of the "fifth" cell. A possible chemoreception mechanism is discussed.

Taste reception mechanisms in the blowfly: evidence of amiloride-sensitive and insensitive receptor sites.

The role of amiloride in the labellar responses to various taste stimuli in the blowfly Protophormia terraenovae was studied with the aim of ascertaining whether amiloride-sensitive cation conductances are present in the chemosensory systems of insects. Results include that: 1) amiloride has no effect on the "salt" cell response to any stimulus; 2) amiloride decreases the "sugar" cell response to fructose, but does not affect that to sucrose; 3) the effects of amiloride on the responses of the "water" cell and the "fifth" cell are less clearly definable, due to the probable superimposition of osmotic mechanisms in the former and the poorly known response modalities of the water. In conclusion, amiloride-sensitive receptor sites seem to exist also in insects. However, unlike most vertebrates investigated, they are principally located in the sugar receptor cell, not on the salt cell.

Saccharin stimulates the "deterrent" cell in the blowfly: behavioral and electrophysiological evidence.

In the attempt to gain more information on the mechanisms underlying bitter and/or sweet taste reception, we have investigated the responses of labellar chemosensilla in the blowfly Protophormia terraenovae to Na-saccharin, as compared to sweet stimuli (sucrose or fructose) and bitter stimuli (denatonium benzoate or amiloride). Electrophysiological and behavioral results indicate that the sweetener Na-saccharin inhibits the "sugar" cell in the labellar taste sensilla of the blowfly P. terraenovae. In multichoice preference tests, flies ingested more of the solutions containing sugar to those with sugar+Na-saccharin. This finding is in good agreement with the spike frequency reduction observed for the "sugar" cell activity. Analysis of the spike discharges also shows a positive dose-response for the "deterrent" cell following stimulation with Na-saccharin and denatonium benzoate. Flies drank any of the Na-saccharin solutions, regardless of their concentration, less than water, thus indicating a weak deterring effect on water drinking. The prevailing activation of the "deterrent" cell by stimulation with Na-saccharin is not directly coupled with a coherent behavioral output. Cross adaptation was found to occur between responses to Na-saccharin and denatonium benzoate or amiloride regardless of the order of adapting stimuli. In the case of sweet stimuli, cross adaptation occurred when the adapting stimulus was Na-saccharin, but it did not when the adapting stimuli were sucrose or fructose. Addition of Na-saccharin to both sugars significantly depressed the spike firing frequency, while an increase was observed with denatonium benzoate or amiloride.

Malignant eccrine spiradenoma. Case report and review of the literature.

Malignant eccrine spiradenoma is an exceedingly rare tumor. A case of a 72-year-old women with this highly aggressive malignancy arising from a long-standing lower leg lesion is reported. Management during the course of disease included surgery, radiation therapy (RT), hyperthermic limb perfusion chemotherapy, and chemotherapy. The patient died of her disease, with widespread metastatic disease 20 months after the diagnosis. A review of the literature is presented, and treatment considerations are summarized.

Structural quantitative information on the active sites of hemocyanins and related model compounds by the XAS approach: the role of multiple-scattering calculations.

In this contribution, we will present an overview of the role of the multiple scattering (MS) calculations in the X-ray absorption spectroscopy (XAS) approach in order to extract from experimental data quantitative structural information on the active sites of the hemocyanin derivatives and of the related model compounds considered.

Biofiltration in chronic uremia: evaluation of long-term efficiency and hemodynamic tolerance with Swan-Ganz catheter.

Biochemical data and clinical tolerance were evaluated in eight uremic patients treated by Biofiltration (BF) for 5-20 months. In four patients hemodynamic parameters were monitored with a Swan-Ganz catheter during a session of BF. BF provides long-term biochemical safety and improved tolerance to fluid removal.

Effect of serotonin and calcium on the supercontractile muscles of the adult blowfly crop.

Bioassays and electrophysiological recordings were conducted to determine the role of serotonin and calcium on the supercontractile pump muscles of the diverticulated crop of adult blowflies. Using in situ crop preparations, serotonin was found to significantly increase the rates of contractions of a specific pump in the crop wall, pump P4. The addition of the serotonin antagonist, mianserin, or calcium free saline, both significantly reduced the contraction rates of this pump. Recordings, using suction electrodes from pump P4, confirm the in situ bioassay data and show that serotonin promotes muscle activity in empty crops in which no pump activity is normally observed. Moreover, our data indicate the crucial role of extracellular calcium ions in crop pump contractile activity. These results provide new information on how the crop of adult dipterans is modulated and suggest that serotonin, possibly supplied by neurons in the thoracico-abdominal neural plexus, may be involved in modulating the pumping of crop contents into the midgut for digestion or triggering antiperistalsis from the foregut in the process known as regurgitation or 'bubbling'.

Effects of a new mixture of essential amino acids (Aminotrofic(®)) in malnourished haemodialysis patients.

The aim of this study was to verify the clinical efficacy of a diet associated with already commercially available oral amino acid functional cluster (AFC) compared to the administration of a diet associated with a nitrogen protein-based supplement (casein) in antagonizing malnutrition in patients with Chronic renal failure (CRF) undergoing haemodialysis. The secondary aim was to assess the changes in protein levels during the acute phase such as the expression of inflammatory cytokines. Twenty patients in haemodialysis aged between 18 and 85 of both genders (13 m, 7f) were recruited, randomized and divided into two groups and treated for 4 months respectively with: (1) oral AFC supplement (*)8 g/die: group A, and (2) oral supplementation of a protein nitrogenous mixture compared to AFC with a casein protein source) of 6.6 g: group P. During the initial assessment and thereafter on a monthly basis all patients underwent the following: Dietary recall 24 h; Anthropometric: Weight, height, BMI, expected dry weight, actual weight; Biochemical: Albumin, transferrin, Na, K, Cl, Ca, P, Mg, long-interval creatinine (Aminotrofic(®): Errekappa Euroterapici, Milano) pre-albumin, α1 acid glycoprotein, C reactive protein (CRP), protein nitrogen appearance (PNA); Instrumental: Handgrip strength evaluation, Calorimetry by means of Armband, Bio-impedance analysis (BIA), Spitzer Index (quality of life), Subjective Global Assessment Generated by the patient (PG SGA). Considering the nutritional parameters, no significant differences concerning dry weight emerged between the beginning (T0) and the end (T4) (weight A to T0: kg 64.41 ± 6.34; weight A to T4: kg 64.51 ± 7.05: P = NS; weight P to T0: kg 60.17 ± 11.94; weight P to T4: kg 59.86 ± 11.43: P = NS); biochemical parameters, significant differences were observed only for two parameters: pre-albumin (Pre-albumin A to T0 30.12 ± 7.23; Pre-albumin A to T4: 28.91 ± 5.8; Pre-albumin P to T0 22.51 ± 6.04; Pre-albumin P to T4: 26.10 ± 9.82), and Transferrin (Transferrin A to T0 171.77 ± 28.87 mg/dL, Transferrin A to T4: 181.44 ± 38.83 mg/dL: P < 0.005; Transferrin P to T0 160.29 ± 27.46 mg/dL, Transferrin P to T4: 146.57 ± 24.96 mg/dL: P < 0.005), but not in other parameters. From a nutritional perspective, after 4 months of treatment an increase in protein synthesis was noted in group A compared to group P which was proved by the significant increase of transferrin. This pilot study suggests the AFC oral supplementation may represent a valid alternative to intradialytic parenteral treatment and may also allow for an improvement in blood chemical values and nutritional status.

Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase.

The catalase from Proteus mirabilis peroxide-resistant bacteria is one of the most efficient heme-containing catalases. It forms a relatively stable compound II. We were able to prepare samples of compound II from P. mirabilis catalase enriched in (57)Fe and to study them by spectroscopic methods. Two different forms of compound II, namely, low-pH compound II (LpH II) and high-pH compound II (HpH II), have been characterized by Mössbauer, extended X-ray absorption fine structure (EXAFS) and UV-vis absorption spectroscopies. The proportions of the two forms are pH-dependent and the pH conversion between HpH II and LpH II is irreversible. Considering (1) the Mössbauer parameters evaluated for four related models by density functional theory methods, (2) the existence of two different Fe-O(ferryl) bond lengths (1.80 and 1.66 A) compatible with our EXAFS data and (3) the pH dependence of the alpha band to beta band intensity ratio in the absorption spectra, we attribute the LpH II compound to a protonated ferryl Fe(IV)-OH complex (Fe-O approximately 1.80 A), whereas the HpH II compound corresponds to the classic ferryl Fe(IV)=O complex (Fe=O approximately 1.66 A). The large quadrupole splitting value of LpH II (measured 2.29 mm s(-1) vs. computed 2.15 mm s(-1)) compared with that of HpH II (measured 1.47 mm s(-1) vs. computed 1.46 mm s(-1)) reflects the protonation of the ferryl group. The relevancy and involvement of such (Fe(IV)=O/Fe(IV)-OH) species in the reactivity of catalase, peroxidase and chloroperoxidase are discussed.

Glucose infusion test: a new screening test for vascular access recirculation.

BACKGROUND: Vascular access recirculation is an important cause of diminished dialysis efficiency. We propose a new screening test based on glucose infusion as a tracer for recirculation. METHODS: The glucose infusion test (GIT) protocol comprises a basal blood sample (A) from the arterial port, a 5 mL bolus of 20% glucose into the venous chamber (time 0), followed by a second sample (B) in four seconds (from 13 to 17 s with QB 300 mL/min) from the same port. The blood glucose level is determined at the bedside on A and B with a reflectance photometer (CV 1.8%). Interpretation of the test is straightforward: If B = A, there is no recirculation, whereas if B > A, recirculation can be calculated from the regression equation: 0.046 x (B - A) + 0.07, obtained from in vitro tests reproducing artificial recirculation at 0, 5, and 10%. To validate this new method in vivo, we compared GIT and the urea test on 39 hemodialysis patients, obtaining a good correlation (r = 0.93). The two tests were considered positive (recirculation present) when the lower 95% confidence intervals were more than zero. RESULTS: Our patients were divided into two groups: those with (22 out of 39, mean recirculation 11.8%) or without recirculation (17 out of 39, mean 0.06%). The urea test did not recognize 7 out of 22 patients because they had a small recirculation below the urea test limit of detection. CONCLUSIONS: GIT was more sensitive (detection limit 0.3%), simpler, and immediate in showing the results than the urea test. It is an accurate and low-cost technique for screening and follow-up of vascular access in a dialysis unit.

Sugar reception in the blowfly: a possible Ca(++) involvement.

The present study investigates the effects of W-7 (a calmodulin antagonist involved in the Ca(++) cascade) on the response of the 'sugar' and 'water' cells of labellar chemosensilla in the blowfly Protophormia terraenovae to stimulation with sucrose or fructose. In order to ascertain whether Ca(++) conductance is involved, the effects of EGTA, one of the most used Ca(++) chelating agent, and of SK&F-96365, an inhibitor of receptor mediated calcium influx, were also studied. Our electrophysiological data indicate that W-7 addition strongly depresses the 'sugar' chemoreceptor response to both sugars and in the case of sucrose stimulation also influences adaptation rate. The Ca(++) chelator has no significant effects on the response of the 'sugar' cell following stimulation with sucrose, but lowers fructose stimulating effectiveness. In the presence of SK&F-96365 both sucrose and fructose responses are inhibited. A possible transduction mechanism for sugar reception is discussed.

Sugar response differences related to sensillum type and location on the labella of Protophormia terraenovae: a contribution to spatial representation of the stimulus.

The chemoreceptor spike activity in response to sucrose in the concentration range 1-500mM was recorded from each of the 11 Intermediate and 13 Large labellar sensilla in the blowfly Protophormia terraenovae. The results showed that: (1) three of the four cells present in each sensillum are activated by sucrose stimulation; (2) differences between the Large and Intermediate types exist in the dose-response profiles of one of these cells (the 'water' cell), possibly reflecting different sugar receptor site populations on the dendritic membranes of homologous cells in the two types; (3) sensilla of both types are differentially responsive to sucrose solutions according to their location on the labellum. These differences may provide elements for a spatial representation of the stimulus source within the sensory coding process.