Fluoride varnishes containing calcium glycerophosphate: fluoride uptake and the effect on in vitro enamel erosion

OBJECTIVES Calcium glycerophosphate (CaGP) was added to fluoride varnishes to analyze their preventive effect on initial enamel erosion and fluoride uptake: potassium hydroxide (KOH)-soluble and KOH-insoluble fluoride bound to enamel. MATERIALS AND METHODS This study was carried out in two parts. Part 1: 108 enamel samples were randomly distributed into six varnish groups: base varnish (no active ingredients); Duraphat® (2.26 %NaF); Duofluorid® (5.63 %NaF/CaF2); experimental varnish 1 (1 %CaGP/5.63 %NaF/CaF2); experimental varnish 2 (5 %CaGP/5.63 %NaF/CaF2); and no varnish. Cyclic demineralization (90 s; citric acid, pH = 3.6) and remineralization (4 h) was made once a day, for 3 days. Change in surface microhardness (SMH) was measured. Part 2: 60 enamel samples were cut in half and received no varnish (control) or a layer of varnish: Duraphat®, Duofluorid®, experimental varnishes 1 and 2. Then, KOH-soluble and KOH-insoluble fluoride were analyzed using an electrode. RESULTS After cyclic demineralization, SMH decreased in all samples, but Duraphat® caused less hardness loss. No difference was observed between varnishes containing CaGP and the other varnishes. Similar amounts of KOH-soluble and insoluble fluoride was found in experimental varnish 1 and Duofluorid®, while lower values were found for experimental varnish 2 and Duraphat®. CONCLUSION The addition of CaGP to fluoride varnishes did not increase fluoride bound to enamel and did not enhance their protection against initial enamel erosion. CLINICAL RELEVANCE We observe that the fluoride varnishes containing CaGP do not promote greater amounts of fluoride bound to enamel and that fluoride bound to enamel may not be closely related to erosion prevention.

Iron uptake and ferrokinetics in healthy male subjects of an iron-based oral phosphate binder (SBR759) labeled with the stable isotope 58 Fe

SBR759 is a novel polynuclear iron(III) oxide–hydroxide starch·sucrose·carbonate complex being developed for oral use in chronic kidney disease (CKD) patients with hyperphosphatemia on hemodialysis. SBR759 binds inorganic phosphate released by food uptake and digestion in the gastro-intestinal tract increasing the fecal excretion of phosphate with concomitant reduction of serum phosphate concentrations. Considering the high content of ∼20% w/w covalently bound iron in SBR759 and expected chronic administration to patients, absorption of small amounts of iron released from the drug substance could result in potential iron overload and toxicity. In a mechanistic iron uptake study, 12 healthy male subjects (receiving comparable low phosphorus-containing meal typical for CKD patients: ≤1000 mg phosphate per day) were treated with 12 g (divided in 3 × 4 g) of stable 58Fe isotope-labeled SBR759. The ferrokinetics of [58Fe]SBR759-related total iron was followed in blood (over 3 weeks) and in plasma (over 26 hours) by analyzing with high precision the isotope ratios of the natural iron isotopes 58Fe, 57Fe, 56Fe and 54Fe by multi-collector inductively coupled mass spectrometry (MC-ICP-MS). Three weeks following dosing, the subjects cumulatively absorbed on average 7.8 ± 3.2 mg (3.8–13.9 mg) iron corresponding to 0.30 ± 0.12% (0.15–0.54%) SBR759-related iron which amounts to approx. 5-fold the basal daily iron absorption of 1–2 mg in humans. SBR759 was well-tolerated and there was no serious adverse event and no clinically significant changes in the iron indices hemoglobin, hematocrit, ferritin concentration and transferrin saturation.

Effects of PEG-Induced Water Deficit in Solanum nigrum on Zn and Ni Uptake and Translocation in Split Root Systems

Drought strongly influences root activities in crop plants and weeds. This paper is focused on the performance of the heavy metal accumulator Solanum nigrum, a plant which might be helpful for phytoremediation. The water potential in a split root system was decreased by the addition of polyethylene glycol (PEG 6000). Rubidium, strontium and radionuclides of heavy metals were used as markers to investigate the uptake into roots, the release to the shoot via the xylem, and finally the basipetal transport via the phloem to unlabeled roots. The uptake into the roots (total contents in the plant) was for most makers more severely decreased than the transport to the shoot or the export from the shoot to the unlabeled roots via the phloem. Regardless of the water potential in the labeling solution, 63Ni and 65Zn were selectively redistributed within the plant. From autoradiographs, it became evident that 65Zn accumulated in root tips, in the apical shoot meristem and in axillary buds, while 63Ni accumulated in young expanded leaves and roots but not in the meristems. Since both radionuclides are mobile in the phloem and are, therefore, well redistributed within the plant, the unequal transfer to shoot and root apical meristems is most likely caused by differences in the cell-to-cell transport in differentiation zones without functional phloem (immature sieve tubes).

Trypanosoma brucei Bloodstream Forms Depend upon Uptake of myo-Inositol for Golgi Complex Phosphatidylinositol Synthesis and Normal Cell Growth

myo-Inositol is a building block for all inositol-containing phospholipids in eukaryotes. It can be synthesized de novo from glucose-6-phosphate in the cytosol and endoplasmic reticulum. Alternatively, it can be taken up from the environment via Na(+)- or H(+)-linked myo-inositol transporters. While Na(+)-coupled myo-inositol transporters are found exclusively in the plasma membrane, H(+)-linked myo-inositol transporters are detected in intracellular organelles. In Trypanosoma brucei, the causative agent of human African sleeping sickness, myo-inositol metabolism is compartmentalized. De novo-synthesized myo-inositol is used for glycosylphosphatidylinositol production in the endoplasmic reticulum, whereas the myo-inositol taken up from the environment is used for bulk phosphatidylinositol synthesis in the Golgi complex. We now provide evidence that the Golgi complex-localized T. brucei H(+)-linked myo-inositol transporter (TbHMIT) is essential in bloodstream-form T. brucei. Downregulation of TbHMIT expression by RNA interference blocked phosphatidylinositol production and inhibited growth of parasites in culture. Characterization of the transporter in a heterologous expression system demonstrated a remarkable selectivity of TbHMIT for myo-inositol. It tolerates only a single modification on the inositol ring, such as the removal of a hydroxyl group or the inversion of stereochemistry at a single hydroxyl group relative to myo-inositol.

Positron emission mammography in the diagnosis of breast cancer. Is maximum PEM uptake value a valuable threshold for malignant breast cancer detection?

AIM To evaluate the diagnostic value (sensitivity, specificity) of positron emission mammography (PEM) in a single site non-interventional study using the maximum PEM uptake value (PUVmax). PATIENTS, METHODS In a singlesite, non-interventional study, 108 patients (107 women, 1 man) with a total of 151 suspected lesions were scanned with a PEM Flex Solo II (Naviscan) at 90 min p.i. with 3.5 MBq 18F-FDG per kg of body weight. In this ROI(region of interest)-based analysis, maximum PEM uptake value (PUV) was determined in lesions, tumours (PUVmaxtumour), benign lesions (PUVmaxnormal breast) and also in healthy tissues on the contralateral side (PUVmaxcontralateral breast). These values were compared and contrasted. In addition, the ratios of PUVmaxtumour / PUVmaxcontralateral breast and PUVmaxnormal breast / PUVmaxcontralateral breast were compared. The image data were interpreted independently by two experienced nuclear medicine physicians and compared with histology in cases of suspected carcinoma. RESULTS Based on a criteria of PUV>1.9, 31 out of 151 lesions in the patient cohort were found to be malignant (21%). A mean PUVmaxtumour of 3.78 ± 2.47 was identified in malignant tumours, while a mean PUVmaxnormal breast of 1.17 ± 0.37 was reported in the glandular tissue of the healthy breast, with the difference being statistically significant (p < 0.001). Similarly, the mean ratio between tumour and healthy glandular tissue in breast cancer patients (3.15 ± 1.58) was found to be significantly higher than the ratio for benign lesions (1.17 ± 0.41, p < 0.001). CONCLUSION PEM is capable of differentiating breast tumours from benign lesions with 100% sensitivity along with a high specificity of 96%, when a threshold of PUVmax >1.9 is applied.

The Gas6-Axl Interaction Mediates Endothelial Uptake of Platelet Microparticles.

Upon activation, platelets release plasma-membrane derived microparticles (PMPs) exposing phosphatidylserine (PS) on their surface. The function and clearance mechanism of these MPs are incompletely understood. As they are pro-coagulant and potentially pro-inflammatory, rapid clearance from the circulation is essential for prevention of thrombotic diseases. The tyrosine kinase receptors Tyro3, Axl and Mer (TAMs) and their ligands protein S and Gas6 are involved in the uptake of PS-exposing apoptotic cells in macrophages and dendritic cells. Both TAMs and their ligands are expressed in the vasculature, the functional significance of which is poorly understood. In this study we investigated how vascular TAMs and their ligands may mediate endothelial uptake of PMPs. PMPs, generated from purified human platelets, were isolated by ultracentrifugation and labeled with biotin or PKH67. The uptake of labeled MPs in the presence of protein S and Gas6 in human aortic endothelial cells (HAEC) and human umbilical vein endothelial cells (HUVEC) was monitored by flow cytometry, western blotting and confocal/electron microscopy. We found that both endothelial cell types can phagocytose PMPs, and using TAM-blocking antibodies or siRNA knock-down of individual TAMs we show that the uptake is mediated by endothelial Axl and Gas6. As circulating PMPs-levels were not altered in Gas6-/- mice compared to Gas6+/+ mice, we hypothesize that the Gas6-mediated uptake is not a means to clear the bulk of circulating PMPs but may serve to phagocytose PMPs locally generated at sites of platelet activation and as a way to affect endothelial responses.

Effect of mannitol and cold treatments on phosphate uptake and protein phosphorylation in Lemna minor (L.) plants

This report is aimed at elucidating the effect of mannitol and cold treatments on P uptake and protein phosphorylation in Lemna minor plants. Duckweed p lants were incu bated in the presence of [32P]or [33P]Pi in half-strength phosphate deprived E-medium under constant light regime for 1.5 h. Total plant protein extracts (pellet and supernatant) were then prepared and subjected to IEF x SDS-PAGE. To analyse the effect of the stresses on P uptake and protein labelling, Lemna minor plants were preincubated with 0.1, 0.5 mol · L-1 mannitol and at 4°C respectively, for 4 hours, before adding labelled orthophosphate. The results show that the general protein phosphorylation (including LHCII) is related to the level of P uptake. Radioactive phosphate incorporation is stimulated by a low concentration of mannitol (0.1 mol · L-1) but reduced by 0.5 mol · L-1 mannitol and cold stress in planta. The labelling into proteins is affected neither when stresses were applied to the plants after incubation with labelled orthophosphate, nor after in vitro protein phosphorylation. This indicates that general protein kinase activities in vivo are strictly limited by P uptake. A marked accumulation of soluble hexoses (mainly sucrose, glucose, and fructose) is observed under imposed stress, suggesting that the inhibition of P uptake in response to hyperosmotic and cold stresses is mediated by sugar accumulation in situ. However, metabolisable sugars like glucose did not alter the entry of phosphate at concentrations of 0.5 mol · L-1, showing that the chemical nature of the osmoticum influences P uptake.

Chromium uptake and adsorption in marine phytoplankton - Implications for the marine chromium cycle

Using the radioisotope 51Cr, we investigated the controls of cellular Cr accumulation in an array of marine phytoplankton grown in environmentally relevant Cr concentrations (1–10 nM). Given the affinity of Cr(III) for amorphous Fe-hydroxide mineral surfaces, and the formation of these mineral phases on the outside of phytoplankton cells, extracellular Cr was monitored in a model diatom species (Thalassiosira weissflogii) as extracellular Fe concentrations varied. Extracellular Cr in T. weissflogii increased with increasing extracellular Fe, demonstrating that Cr may be removed from seawater via extracellular adsorption to phytoplankton. Short-term Cr(VI) and Cr(III) uptake experiments performed with T. weissflogii demonstrated that Cr(III) was the primary oxidation state adsorbing to cells and being internalized by them. Cellular Cr:C ratios (<0.5 μmol Cr mol C−1) of the eight phytoplankton species surveyed were significantly lower than previously reported Cr:C ratios in marine particles with a high biogenic component (10–300 μmol Cr mol C−1). This indicates that Cr(III) likely accumulates in marine particles due to uptake and/or adsorption. Mass balance calculations demonstrate that surface water Cr deficits can be explained via loss of Cr(III) to exported particles, thereby providing a mechanism to account for the nutrient depth profile for Cr in modern seawater. Given the large fractionation of stable Cr isotopes during Cr(VI) reduction, Cr(III) associated with exported organic carbon is likely enriched in lighter isotopes. Most sedimentary Cr isotope studies have thus far neglected internal fractionating processes in the marine Cr cycle, but our data indicate that loss of Cr to exported particles may be traced in the sedimentary d53Cr record.

Estimating the uptake of traffic-derived NO2 from 15N abundance in Norway spruce needles

The 15N ratio of nitrogen oxides (NOx) emitted from vehicles, measured in the air adjacent to a highway in the Swiss Middle Land, was very high [δ15N(NO2) = +5.7‰]. This high 15N abundance was used to estimate long-term NO2 dry deposition into a forest ecosystem by measuring δ15N in the needles and the soil of potted and autochthonous spruce trees [Picea abies (L.) Karst] exposed to NO2 in a transect orthogonal to the highway. δ15N in the current-year needles of potted trees was 2.0‰ higher than that of the control after 4 months of exposure close to the highway, suggesting a 25% contribution to the N-nutrition of these needles. Needle fall into the pots was prevented by grids placed above the soil, while the continuous decomposition of needle litter below the autochthonous trees over previous years has increased δ15N values in the soil, resulting in parallel gradients of δ15N in soil and needles with distance from the highway. Estimates of NO2 uptake into needles obtained from the δ15N data were significantly correlated with the inputs calculated with a shoot gas exchange model based on a parameterisation widely used in deposition modelling. Therefore, we provide an indication of estimated N inputs to forest ecosystems via dry deposition of NO2 at the receptor level under field conditions.

Hypersensitivity of an Arabidopsis Sugar Signaling Mutant toward Exogenous Proline Application

In transgenic Arabidopsis a patatin class I promoter from potato is regulated by sugars and proline (Pro), thus integrating signals derived from carbon and nitrogen metabolism. In both cases a signaling cascade involving protein phosphatases is involved in induction. Other endogenous genes are also regulated by both Pro and carbohydrates. Chalcone synthase (CHS) gene expression is induced by both, whereas the Pro biosynthetic Δ1-pyrroline-5-carboxylate synthetase (P5CS) is induced by high Suc concentrations but repressed by Pro, and Pro dehydrogenase (ProDH) is inversely regulated. The mutantrsr1-1, impaired in sugar dependent induction of the patatin promoter, is hypersensitive to low levels of external Pro and develops autofluorescence and necroses. Toxicity of Pro can be ameliorated by salt stress and exogenously supplied metabolizable carbohydrates. The rsr1-1 mutant shows a reduced response regarding sugar induction of CHS andP5CS expression. ProDH expression is de-repressed in the mutant but still down-regulated by sugar. Pro toxicity seems to be mediated by the degradation intermediate Δ1-pyrroline-5-carboxylate. Induction of the patatin promoter by carbohydrates and Pro, together with the Pro hypersensitivity of the mutant rsr1-1, demonstrate a new link between carbon/nitrogen and stress responses.