Ionenreihen in der Kolloidchemie und Biologie

Zusammenfassung Aus obenstehenden Erörterungen folgt, daß die elektrischen Eigenschaften der Biokolloide, welche die Membrane aufbauen, von größter Bedeutung sind für die Permeabilität dieser Membran, so daß die Reihenfolge von Ionen, in Permeabilitätsversuchen bestimmt, Reihenfolgen vorstellen bezüglich dieser elektrischen Eigenschaften. Es sind nun gerade diese elektrischen Eigenschaften, welche wir studiert haben in den Reihenfolgen der Umladungskonzentrationen von möglichst vielen Ionen für verschiedene, gereinigt hergestellte Biokolloide (nicht amphotere, mit verschiedenen ionogenen Gruppen, n. 1. Phosphat-, Karboxyl- und Sulfatgruppen, sowie amphotere mit positiver und negativer Ladung), so daß es gerechtfertigt scheint, die Ergebnisse der Ionenreihen in der Biologie und in der Kolloidchemie miteinander zu vergleichen.     

Dynamic modulation transfer function: a method to characterize the temporal performance of liquid-crystal displays

A method to measure the dynamic modulation transfer function (DMTF) of a liquid-crystal display (LCD) is proposed to characterize its performance when rendering motion images. The method includes a measurement system to capture the temporal luminance variation of a LCD while using a well-designed input data sequence and a simulation model based on smooth pursuit eye tracking and temporal light integration at the human retina. It predicts the perceived performance of a moving sine wave pattern on a LCD and subsequently calculates the DMTF. With this approach, several technologies to reduce motion blur were evaluated and discussed.     

The measurement of small forces by means of a moving coil meter with an application to magnetic susceptibility measurements

Summary A method is described for the measurements of small forces (10⁻⁵ – 10⁻³ newton) on a sample weighing a few grams. This sample is placed on a bar which is fixed on the turning coil of an ordinary switchboard current meter. The force on the sample can be compensated by the Lorentz force on the current through the coil. This method avoids a great many of the usual constructional difficulties of such apparatus and leads to a robust instrument which is easy to handle and to. automatize, thus being of interest for use outside the laboratory. Especially this possibility has induced us to choose as an example a magnetic susceptibility balance. For magnets of field strength up to 20 000 oerstedt the precision obtained for the measured susceptibility amounts to one tenth of a percent.     

Sono-oxidation treatment of humic substances in drinking water.

Currently humic substances are removed from the raw water prior to chlorination by the conventional coagulation and filtration method using aluminium sulphate. Application of high-intensity (> 10 W/cm2) ultrasonic irradiation in conjunction with oxidative process using commercial oxidants H2O2 was investigated as an alternative. Sono-oxidation and sonodegradation of natural and synthetic humic substances have been followed over time by measuring total organic carbon (TOC) and absorbance by ultraviolet spectrometer (UV-VIS). It took approximately 60 min to reduce TOC by half and to have a complete degradation of humic acid.     

Bioanalytical methods for determination of tamoxifen and its phase I metabolites: a review

The selective estrogen receptor modulator tamoxifen is used in the treatment of early and advanced breast cancer and in selected cases for breast cancer prevention in high-risk subjects. The cytochrome P450 enzyme system and flavin-containing monooxygenase are responsible for the extensive metabolism of tamoxifen into several phase I metabolites that vary in toxicity and potencies towards estrogen receptor (ER) alpha and ER beta.An extensive overview of publications on the determination of tamoxifen and its phase I metabolites in biological samples is presented. In these publications techniques were used such as capillary electrophoresis, liquid, gas and thin layer chromatography coupled with various detection techniques (mass spectrometry, ultraviolet or fluorescence detection, liquid scintillation counting and nuclear magnetic resonance spectroscopy). A trend is seen towards the use of liquid chromatography coupled to mass spectrometry (LC-MS). State-of-the-art LC-MS equipment allowed for identification of unknown metabolites and quantification of known metabolites reaching lower limit of quantification levels in the sub pg mL⁻¹ range. Although tamoxifen is also metabolized into phase II metabolites, the number of publications reporting on phase II metabolism of tamoxifen is scarce. Therefore the focus of this review is on phase I metabolites of tamoxifen.We conclude that in the past decades tamoxifen metabolism has been studied extensively and numerous metabolites have been identified. Assays have been developed for both the identification and quantification of tamoxifen and its metabolites in an array of biological samples. This review can be used as a resource for method transfer and development of analytical methods used to support pharmacokinetic and pharmacodynamic studies of tamoxifen and its phase I metabolites.     

Biokolloide als hochmolekulare Elektrolyte. III

Colloid and Polymer Science -     

Epidermal cis-urocanic acid levels correlate with lower specific cellular immune responses after hepatitis B vaccination of ultraviolet B-exposed humans

Urocanic acid (UCA) is a major UV-absorbing chromophore in the epidermis and has been suggested to act as one of the initiators of UV-induced immunosuppression. cis-UCA, the isomer from UCA that is formed upon UV exposure, has been shown to impair some cellular immune responses. cis-UCA levels were determined in a study in which the influence of ultraviolet B (UVB) exposure on immune responses after hepatitis B vaccination in human volunteers was established. A significant increase in cis-UCA levels was found in the skin of UVB-exposed volunteers compared with controls. cis-UCA levels, calculated as the percentage of the total UCA amount, in UVB-exposed volunteers correlated significantly with the cumulative UVB dose received in 5 consecutive days, i.e. the higher the UVB dose (J/m2), the higher the cis-UCA levels (until a cis-UCA plateau was reached in the so-called photostationary state). Correlations between skin cis-UCA levels and immune responses were determined, and they revealed no statistically significant correlations among lymphocyte proliferation responses after either mitogenic stimulation or stimulation with recall antigens. No correlation was found between cis-UCA levels and hepatitis B-specific antibody titers. However, we found a statistically significant negative correlation between cis-UCA levels and hepatitis B-specific lymphocyte proliferation responses when volunteers were irradiated with UVB before hepatitis B vaccination. In other words, volunteers with high cis-UCA levels caused by UVB exposure showed lower cellular immune responses against hepatitis B antigen after hepatitis B vaccination.     

Suppression of Different Phases of Systemic Contact Hypersensitivity by Urocanic Acid Oxidation Productsfn1

On exposure to UV‐B, the epidermal component trans‐urocanic acid (UCA) is not only photoisomerized into cis‐ UCA but will also, at least in part, be photooxidized into UCA oxidation products (UOPs). We hypothesized that UOPs can mimic UV‐induced systemic immunosuppression comparable to the suppressive properties already established for cis‐UCA. A crude mixture of UOPs showed a significant suppression of the sensitization phase of the systemic contact hypersensitivity (CHS) response to picryl chloride (PCI). Three of the UOPs were selected for this study: imidazole‐4‐carboxylic acid (ImCOOH), immidazole‐4‐carboxaldehyde (ImCHO) and imidazole‐4‐acetic acid (ImAc). Effects on the sensitization, elicitation and postelicitation phases of CHS to PCI in BALB/c mice were studied and compared with the effects of cis‐UCA. ImCHO was equally effective at suppressing the sensitization phase as cis‐UCA. The triplet combination of the imidazoles (1:1:1) showed more pronounced suppression than that induced by cis‐UCA. The most effective compounds for the suppression of the elicitation phase appeared to be ImAc and cis‐UCA. Significant suppression of the postelicitation phase was only obtained with the triplet combination of ImCHO, ImCOOH and ImAc, the combination that appeared to be effective at all three tested phases. Because these three UOPs are present in UV‐B‐exposed human stratum corvneum, these compounds may play a role in UV‐B‐induced immunosuppression.