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Biomedical subjects

B Michalke

Publications and source records attributed to B Michalke.

At least 19 recordsLinked to original sources
PubMed2006

Distribution pattern of inhaled ultrafine gold particles in the rat lung.

The role of alveolar macrophages in the fate of ultrafine particles in the lung was investigated. Male Wistar-Kyoto rats were exposed to ultrafine gold particles, generated by a spark generator, for 6 h at a concentration of 88 microg/m3 (4 x 10(6)/cm3, 16 nm modal mobility diameter). Up to 7 days, the animals were serially sacrificed, and lavaged cells and lung tissues were examined by transmission electron microscopy. The gold concentration/content in the lung, lavage fluid, and blood was estimated by inductively coupled plasma-mass spectrometry. Gold particles used were spherical and electron dense with diameters of 5-8 nm. The particles were individual or slightly agglomerated. By inductively coupled plasma-mass spectrometry analysis of the lung, 1945 +/- 57 ng (mean +/- SD) and 1512 +/- 184 ng of gold were detected on day 0 and on day 7, respectively, indicating that a large portion of the deposited gold particles was retained in the lung tissue. In the lavage fluid, 573 +/- 67 ng and 96 +/- 29 ng were found on day 0 and day 7, respectively, which means that 29% and 6% of the retained gold particles were lavageable on these days. A low but significant increase of gold (0.03 to 0.06% of lung concentration) was found in the blood. Small vesicles containing gold particles were found in the cytoplasm of alveolar macrophages. In the alveolar septum, the gold particles were enclosed in vesicles observed in the cytoplasm of alveolar type I epithelial cells. These results indicate that inhaled ultrafine gold particles in alveolar macrophages and type I epithelial cells are processed by endocytotic pathways, though the uptake of the gold particles by alveolar macrophages is limited. To a low degree, systemic particle translocation took place.

Animals↗
PubMed2003

Speciation of Pt(II) and Pt(IV) in spiked extracts from road dust using on-line liquid chromatography-inductively coupled plasma mass spectrometry.

The emission of platinum from automobile catalytic exhaust converters is well known and the accumulation of Pt in road dust has been studied by the analysis of total Pt contents. However, there are few studies on the speciation of the emitted Pt-compounds in the environment. A separation method with HPLC-UV has been developed by Nachtigall et al. [Chromatogr. A 775 (1997) 197] with aqueous standards of Pt(II)- and Pt(IV)-chloro complexes. Due to the limited selectivity and sensitivity of the UV-detection this method is not suitable for Pt-speciation in road dust extracts. Therefore, in this study the method of Nachtigall et al. was modified to realize an on-line coupling to ICP-MS with the advantage of Pt-specific detection. Calibration was performed with aqueous standards and spiked road dust extracts. Calibration curves were linear with low residual standard deviation (1.3-3.1% for the aqueous standards) and approximately 10-times lower detection limits compared to the HPLC-UV-method. Moreover, the stability of the model species was investigated using isocratic as well as gradient separation. Isotopic ratios of 194Pt, 195Pt, 196Pt and 198Pt were determined for quality control. A new mathematical correction method for the HfO-interference on the 195Pt-signal was developed. Additionally, the elution pattern of further elements in the road dust extracts was monitored and total element contents were determined in unspiked road dust extracts.

Calibration↗
PubMed2002

Identification and quantification of metallothionein isoforms and superoxide dismutase in spiked liver extracts using HPLC-ESI-MS offline coupling and HPLC-ICP-MS online coupling.

A two-dimensional chromatographic method for the characterization of metallothionein isoforms (MT) and superoxide dismutase (SOD) in spiked liver extracts was developed for the optimization of extraction procedures from liver samples. Element-specific detection (ICP-MS) and molecule-specific detection (ESI-MS) were applied for maximum species information. A special focus was laid on the quantitative data evaluation (species stoichiometry, calibration with and without matrix, recovery), which is neglected in most MT/SOD publications with hyphenated techniques. Linearity, precision (residual standard deviation of calibration curves <10%), and detection limits (<0.6 mg L(-1) for MT isoforms and 13 mg L(-1) for SOD) prove the suitability of the method for quantification. An alternative quantification is proposed for the extension towards other lesser or even unknown trace element species, especially the native porcine MT and SOD.

Animals↗
PubMed2002

Iodine species and the endocrine system: thyroid hormone levels in adult Danio rerio and developing Xenopus laevis.

Recently a new approach for the analysis of iodinated organic species in human serum has been developed using liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS). This method enables quantification of iodide, T4 and T3, as well as reverse T3 (rT3) and the synthetic precursors of TH, monoiodotyrosine (MIT), and diiodotyrosine (DIT) in a single injection. In this work, the LC-ICP-MS approach was used to analyze whole-body homogenates of adult male and female zebrafish (Danio rerio) and tadpoles of the African clawed frog (Xenopus laevis) at two different developmental stages (NF58 and 61) according to Nieuwkoop and Faber. The data demonstrate that the LC-ICP-MS method was successful at measuring I-, MIT, DIT, T4, T3, and rT3 in these two species. Furthermore, the method also detected five additional iodinated compounds which are currently unidentified.

Animals↗
PubMed2001

Effect of different extraction procedures on the yield and pattern of Se-species in bacterial samples.

Investigations are described to extract Se-species from a bacterial sample. The five extraction methods investigated were: hot water, protease, lysozyme, lysozyme-protease, and HCl hydrolysis. The extraction efficiency was determined by comparing the total amounts of selenium in the sample after pressure digestion with the amounts extracted by the different methods described. Efficiencies were found to be only 1% (hot water), ca. 8% (protease, HCl hydrolysis) or ca. 12% (lysozyme, lysozyme-protease). The Se-peak patterns were compared after investigating the extracts with strong anion exchange chromatography-inductively coupled plasma mass spectrometry (SAX-ICP-MS). Most promising were the lysozyme-assisted procedures, which showed the highest diversity of species. Here, in the protease-lysozyme approach, the protease seemed to break down species that had been extracted by lysozyme from the bacterial wall (murein sacculus). The other approaches seemed not to extract many species. Hot water extraction was completely unsuitable, extracting only low amounts of a single, unknown species.

Bacteria↗
PubMed2000

Study of the copper distribution in contaminated soils of hop fields by single and sequential extraction procedures.

Hop growing in Bavaria requires the use of copper containing fungicides against mildew, which results in an accumulation of copper in the upper soils to concentrations of up to approximately 450 mg kg(-1). The naturally occurring concentration of copper is approximately 10-15 times lower. Several single and sequential extractions were performed in parallel to the determination of total copper content after aqua regia digestion. By these means copper mobility and retention, its availability to plants as well as its distribution in soils was assessed. Three agricultural soils and two soils from fallow land have been analysed to elucidate whether the copper distribution changes in relation to agricultural activities and to predict environmental risks due to the high copper concentrations. This work also focuses on the difficulties arising from different results when using single and sequential extraction procedures. EDTA, acetic acid, deionised water, ammonium nitrate and calcium chloride were used as single extractants for the functionally defined speciation. EDTA and acetic acid can be regarded as extractants for the plant-available species, while deionised water, NH4NO3 and CaCl2 only release electrostatically weakly bound metals to estimate the mobile species. The extraction behaviour of copper in these procedures is discussed with respect to the quantities extracted from the contaminated and non-contaminated soils. The studies indicate that no vertical copper translocation is observed in the ground, but the main amounts are highly available to plants. Sequential extraction procedures were used for operationally defined speciation, quantifying copper in specific soil phases. The 'five-step extraction scheme' first applied, suggested by the Standard Measurement and Testing Programme of the European Community, overestimated the amounts of copper bound to the residual phase. This was mainly due to the non-specific nature of the reagents for the organic/sulfidic and crystalline iron oxide fraction. A second reason could be the fact that this scheme was developed for sediment and not for soil analysis. Therefore, the sequential extraction has been applied using an adapted method of Zeien and Bruemmer, using different extractants for the two phases. The copper distribution was different, showing that approximately 40-50% of the total copper was bound to the organic fraction and approximately 15-30% could be extracted with the iron oxides. The amounts in the residual fraction were much lower. After comparing the results of the different extraction procedures the environmental behaviour of copper and its risks for plants, micro-organisms and groundwater is discussed in brief.

Agriculture↗
PubMed2000

Long-term monitoring of arsenic and selenium species in contaminated groundwaters by HPLC and HG-AAS.

The long-term concentration and distribution of species of arsenic and selenium in contaminated groundwaters from Kelheim was monitored. Most of the groundwater wells contained elevated concentrations of iron, manganese and sulfur. Arsenic (III), arsenic (V), selenium (IV) and selenium (VI) were separated using high performance liquid chromatography (HPLC) based on phosphate buffers and collected in fractions. Due to the complex matrix, the fractions were analyzed element-specifically by hydride-generating atomic absorption spectrometry (HG-AAS). The combination of HPLC and HG-AAS was selected due to the authors' intention of developing an easy-to-handle, but nonetheless reliable, method suitable for the long-term monitoring of species distribution in an almost routine way, and taking account of the threshold values of 10 microg/l for each element, indicated by German drinking water regulations. To enhance the reliability of the method, analytical quality control experiments were carried out. When applied to groundwater wells from Kelheim (Germany) they revealed that arsenic (V) and selenium (VI) were the dominating species. The presence of arsenic (III) and selenium (IV) was assumed to be supported by organic matter.

Arsenic↗
PubMed2000

Method developments for iodine speciation by reversed-phase liquid chromatography-ICP-mass spectrometry.

Method developments are described for a iodine speciation method. This method is based on a reversed-phase liquid chromatography separation combined with inductively coupled plasma-mass spectrometry detection. Investigations are performed concerning the methanol tolerance/stability of inductively coupled plasma, postcolumn oxidation/volatilization of iodine from species, influences of buffer pH, and column temperature on separation efficiency. The experiments focused on six iodine species, namely iodine, monoiodothyrosine, di-iodothyrosine, tri-iodothyronine, reversed tri-iodothyronine, and thyroxin. Detection limits were determined between 0.08 and 1.5 microg/L (iodine related), dependent on species. Appplications on a urine sample were performed, showing iodide as the predominant iodine species.

Buffers↗
PubMed2000

Iodine speciation in human serum by reversed-phase liquid chromatography-ICP-mass spectrometry.

Reversed-phase liquid chromatography-inductively coupled plasma mass spectrometric hyphenation was used for iodine speciation in human serum. First investigations showed that iodine species nearly quantitatively were eluted in the void volume. The result indicated that protein-linked thyroid hormones were not interacting with the stationary phase, thus being not retained. Investigations were performed about T4-TBG (thyroxin-thyroxin-binding globulin) complex generation and its retention during chromatography. It was shown that T4-TBG was not retained on the column. Therefore, a protease treatment was introduced for serum sample preparation. The analysis of "normal" sera (after protease) gave reasonable results lying in the range published in literature: I-:11; di-iodothyrosine (DIT): 2.1; mono-iodothyrosine (MIT): 1.6; reversed tri-iodothyronine (rT3): 3.9; T3: 5.9; T4: 60; each micrograms iodine per liter. The method also proved to recognize abnormalities in a pathologic serum, having rT3 as the predominant species. In this case the method obviously was superior compared to standard immunoassay methods, as it is monitoring the iodine in the species (physiologically active iodine species), whereas immunoassay methods may sometimes detect deiodinated (inactive) compounds.

Blood Chemical Analysis↗
PubMed1999

Antimony speciation in environmental samples by interfacing capillary electrophoresis on-line to an inductively coupled plasma mass spectrometer.

Antimony is a widely distributed trace element of ecotoxicological interest. A pathway via bioalkylation of inorganic Sb species is discussed in the literature, resulting in organically bound Sb species. Therefore, Sb speciation becomes increasingly a matter of interest for risk assessment in the environment. This contribution investigates the possibilities of CE on-line hyphenated to ICP-MS for Sb speciation. Two methods are employed, both highly resolving the species but only one preserving the species stability. The latter used Na2HPO4/NaH2PO4, 20 mM, pH 5.6 as the background electrolyte and NaOH or acetic acid as stacking electrolyte 1 or stacking electrolyte 2, respectively. Detection limits of 0.1 microgram/1-0.7 microgram/1, depending on species, were achieved. When analysing liquid phases from fouling and sewage sludge up to eight antimony species were detected. Sb (V) as well as methylated Sb species were found.

Antimony↗
PubMed1999

Platinum speciation in clinical and environmental samples: scrutiny of data obtained by using electrophoresis techniques (flatbed and capillary).

The commercially available and widely used flatbed electrophoresis apparatus PhastSystem and MultiPhor II (Amersham Pharmacia Biotech, Uppsala, Sweden) were checked for the possible release of significant amounts of platinum from the electrodes during isoelectric focusing (IEF) and native polyacrylamide gel electrophoresis (PAGE). Capillary electrophoresis (CE; Biofocus 3000; Bio-Rad, Munich, Germany) in zone electrophoresis (CZE) mode was investigated for the same purpose. Platinum analysis was done by inductively coupled plasma mass spectrometry (quadrupole and magnetic sector field) either "off-line" for all flatbed gels or "on-line" for the CE measurements. The buffers and process chemicals did not significantly leach platinum from the electrodes. During flatbed electrophoresis, application of the electrical field, however, released high platinum amounts exceeding by far the amount of platinum originally present in the sample. For CE, no platinum was released from the electrodes. The results are strongly dependent on the system and conditions used. The results presented in this paper underline the necessity to replace the platinum electrodes with ultrapure gold electrodes whenever investigating platinum species. Previous literature data, in which electrophoresis was used for platinum speciation without mentioning the platinum recoveries, becomes questionable.

Electrodes↗
PubMed1999

Iodine speciation in biological samples by capillary electrophoresis-inductively coupled plasma mass spectrometry.

A hyphenation of capillary electrophoresis (CE) to inductively coupled plasma mass spectrometry (ICP-MS) was employed for the speciation of iodine. The separation method used a buffer sandwich of phosphate (pH 2.3), NaOH, sodium dodecyl sulfate (SDS) and borate buffer (pH 8.3) for stacking, aiming at sufficient separation of iodide, iodate, thyroxine (T4) and triiodothyronine (T3). These four iodine species were separated within 15 min and subsequently detected during a pressure-driven detection step (baseline-separated) at 19.5, 29.1, 36.6 and 42.2 s. The detection limits were determined at 0.08 microg I/L (iodide), 0.3 microg I/L (iodate), 3.5 microg I/L (thyroxine) and 2.5 microg I/L (triiodothyronine). This method was applied on iodine speciation in human serum ("healthy" and after thyroid gland operation) and urine. The serum from the healthy person contained iodide (13 microg I/L), T4 (61 microg I/L) and T3 (7.5 microg I/L), whereas the serum from the thyroid-operated person lacked T3. As no "free" I-hormones are known in serum, the role of the thyroid hormone binding globulin (TBG) was investigated. We found that spiked T4 or T3 immediately bound to TBG. Investigations on human urine showed only a peak for iodide.

Electrophoresis, Capillary↗
PubMed1998

Application of capillary zone electrophoresis-inductively coupled plasma mass spectrometry and capillary isoelectric focusing-inductively coupled plasma mass spectrometry for selenium speciation.

The high resolution potential of capillary electrophoresis (CE) makes CE techniques valuable for separations of selenium species, both, organic and inorganic. Such effective separations of charged species are possible using the CZE mode (Z = zone). Very powerful separations can be achieved by capillary isoelectric focusing, when analysing molecules showing different isoelectric points (pI) values, such as organic Se species. Inductively coupled plasma (ICP) MS is an element-specific multi-element detector, providing extremely low detection limits. The combination of CE with ICP-MS promises a powerful tool for metal speciation. Therefore, an online hyphenation of CE [using capillary zone electrophoresis (CZE) or capillary isoelectric focusing (cITP) model] with ICP-MS, which was developed earlier, was modified and applied to selenium speciation. Separation was differentiated from the detection step during hyphenation. This resulted in short separation times (10 min) and a subsequent detection step lasting 100 s. Firstly, a CZE method was applied, providing a separation of six Se species of interest in one run [Se(IV), Se(VI), selenium carrying glutathione (GSSeSG), selenomethionine (SeM), selenocystine (SeC), selenocystamine (SeCM)]. This CZE method used an alkaline background electrolyte (Na2CO3/NaOH). The Se species were separated sufficiently from each other. Detection limits were calculated as 10 or 20 micrograms Se l-1 for inorganic Se species and 30-50 micrograms Se l-1 for organic Se species. The method was applied to standard mixtures and body fluids like human milk and serum. Secondly, a cIEF separation (pH range 2-10) was employed for organic Se species only in parallel. Detection limits were around 10-30 micrograms Se l-1. The method was applied to standard mixtures and body fluids like human milk and serum.

Electrophoresis, Capillary↗
PubMed1998

Selenium speciation by interfacing capillary electrophoresis with inductively coupled plasma-mass spectrometry.

The high resolution potential of capillary electrophoresis (CE) makes CE techniques valuable for separations of selenium species. Further, inductively coupled plasma-mass spectrometry (ICP-MS) affords element-specific multi-element detection, providing extremely low detection limits. The combination of CE with ICP-MS promises to become a powerful tool for metal speciation. Therefore, an on-line hyphenation of CE with ICP-MS, which was developed earlier (Michalke, B., Schramel, P., Fresenius' J. Anal. Chem. 1997, 257, 594-599), was modified and applied to selenium speciation. For this reason, capillary zone electrophoresis (CZE) methods were developed, providing the possibility to analyze six Se species of interest in one run: Se (IV), Se (VI), selenium carrying glutathione (GSSeSG), selenomethionine (SeM), selenocystine (SeC), and selenocystamine (SeCM). The final CE method used an alkaline background electrolyte (Na2CO3/NaOH) with separation differentiated from the detection step during hyphenation. This resulted in short separation times (10 min) and a subsequent detection step of 100s. The Se species were sufficiently separated from each other and appeared at 7s (SeCM), 16s (Se [VI]), 22s [SeC], 27s (Se [IV]), 35s [SeM] and 56s (GSSeSG) during the detection step. Detection limits were calculated as 10 or 20 microg Se/L for inorganic Se species and 35-50 microg Se/L for organic Se species.

Electrophoresis, Capillary↗
PubMed1998

Capillary electrophoresis interfaced to inductively coupled plasma mass spectrometry for element selective detection in arsenic speciation.

A method is presented to separate and detect six arsenic species by capillary electrophoresis (CE) interfaced to inductively coupled plasma mass spectrometry (ICP-MS). CE was used as a highly resolving separation system, whereas ICP-MS served as an element selective detector providing low detection limits. The special mode of operation included sample stacking and a differentiation of separation and detection. This provided separation and detection of six As species, uncharged and anionic, to be monitored within a single run. Detection limits were calculated according to IUPAC recommendation at 15 microg As/L for As (III), dimethyl arsinic acid (DA), monomethyl arsonic acid (MA) and As (V), or 65 microg As/L for arsenobetaine (AsB) and arsenocholine (AsC). Investigations were focused on possibly occurring interferences, e.g., ArCl+ interference at the monoisotope 75As. Finally, real samples from biomedical field (urine) and environmental field (sewage sludge) were analyzed.

Anions↗
PubMed1997

Selenium speciation in human milk with special respect to quality control.

Selenium- (SE) organo compounds of pooled human milk (7th-14th d after delivery) were separated by centrifugation and subsequent size-exclusion chromatography (SEC) as described in ref. (1). The SEC fractions were used for Se determinations by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) in parallel to identification procedures of the organic ligands by two different capillary zone electrophoresis (CZE) methods. Further, the combination of isotachophoresis- (ITP) CZE with ETV-ICP-MS was used for final identifications. Mass balances were carried out at each analytical step for quality assurance. Reinjection experiments were performed to check the stability of Se-organo compounds during the analytical procedure. These quality-control experiments showed that no species transformations took place during the analytical procedure, and the Se species were native in human milk. The identification and quantification of organic ligands were clear and resulted in values of 2 (+/- 0.2) mg/L GSH/GSeH, 2 (+/- 0.22) mg/L cystamine/Se-cystamine, 4 (+/- 0.4) mg/L cystine/ Se-cystine, and 1 (+/- 0.18) mg/L methionine/Se-methionine. Unfortunately, a differentiation between sulfur (S) and Se analogs was not possible with the applied CE methods. The Se values per organic ligand were determined as 2.5 (+/- 0.23) mg/L associated with GSH (as GSeH), 3.1 (+/- 0.31) mg/L associated with cystamine (as Se-cystamine), 5.2 (+/- 0.4) mg/L associated with cystine (as Se-cystine), and 1 (+/- 0.1) mg/L associated with methionine (as Se-methionine).

Chromatography, Gel↗
PubMed1996

Hyphenation of capillary electrophoresis to inductively coupled plasma mass spectrometry as an element-specific detection method for metal speciation.

A stepwise development for the use of capillary electrophoresis and inductively coupled plasma mass spectrometry (ICP-MS) for speciation investigations is presented. The high resolution power of CE is used for the separation of metal species, whereas ICP-MS is taken for element-specific detection with low detection limits. This contribution starts with an off-line combination of both instruments. Separation and identification of species in model solutions and real samples are shown by scanning UV detection at the CE unit with subsequent metal quantification in peak related fractions, applying electrothermal vaporization ICP-MS. Finally, first separations are demonstrated, using the on-line hyphenation with a laboratory-made nebulizer. Here, standard solutions are separated and monitored by UV and ICP-MS. Stability of electrical current during nebulization was checked and a possibly interfering suction flow was estimated. After optimization sufficient electropherograms were obtained. Advantages and problems are discussed for both modes.

Chemical Fractionation↗