Thyroxin-bindendes Globulin (TBG)

Zum Aufbau einer spezifischen radioimmunologischen Bestimmungsmethode von Thyroxin-bindendem Globulin (TBG) im Serum wurde eine reine TBG-Präparation hergestellt. Die erste Anreicherung des TBG aus humanem Poolplasma um den Faktor 640 wurde mit einer Affinitätschromatographie über Sepharose 4-B erreicht, an die Trijodthyronin (T3) kovalent gebunden war. Die weitere Reinigung mit einer Gesamtanreicherung um einen Faktor von 4500 erfolgte über Anionenchromatographie (QAE- und DEAE-Sephadex A-50) und Affinitätschromatographie mit Concanavalin A (ConA-Sepharose). Die Wiederfindung von TBG über alle Schritte lag bei 20%. Das isolierte TBG, das in der Disc-Elektrophorese in drei verschiedenen Polyacrylamidkonzentrationen bei zwei verschiedenen pH-Werten (pH 7,0 und pH 8,9) als eine homogene Bande zur Darstellung kam, band Thyroxin (T4) oder Trijodthyronin (T3) äquimolar. Als Zeichen einer Mikroheterogenität kamen beim isoelectric focusing im pH-Bereich von 4,0–4,5 drei Banden zur Darstellung. Der indirekt ermittelte Zuckeranteil der TBG-Präparation betrug 15%. Diese TBG-Präparation wurde zur Immunisierung von Kaninchen und zur125Jod-Markierung mit der Chloramin-T-Methode benutzt. Die Präzision des Radioimmunoassay von TBG von Tag zu Tag war mit einem Variationskoeffizienten von 4,3% gut. Die Verdünnungskurven aller bisher geprüften Serumproben — auch bei quantitativen TBG-Varianten — lagen auf der Kalibrierstandardkurve: Hinweise auf eine immunologische Heterogenität des TBG ergaben sich damit nicht. Bei Kontrollpersonen mit einem mittleren TBG-Spiegel von 23,0±4,0 mg/l (x±s) zeigte sich eine zweigipflige Altersabhängigkeit der TBG-Konzentrationen im Serum: In den ersten vier postnatalen Lebenswochen fanden sich die höchsten TBG-Spiegel, die bis zum generationsfähigen Alter abfielen, um jenseits des 50. Lebensjahres wieder anzusteigen. Nach Abschluß der Perinatalphase bestand eine signifikante Korrelation zwischen dem Gesamt-T4 und TBG. Der T4/TBG-Quotient war altersunabhängig konstant (3,2±0,7;x±s) und folglich der geeignete diagnostische Parameter. Ein Geschlechtsunterschied der TBG-Spiegel fand sich in keinem Lebensalter, ebenso konnten keine zyklischen Schwankungen bei Frauen im generationsfähigen Alter nachgewiesen werden. Der bekannte Anstieg der TBG-Spiegel unter Oestrogeneinfluß konnte bei Frauen (Antiovulantien und Gravidität) und bei Männern (Fosfestrol) quantitativ bestätigt werden. Umgekehrt konnte ein Abfall der TBG-Spiegel bei therapeutisch induziertem Oestrogenmangel (Danazol) erstmals aufgezeigt werden. Bei primären Schilddrüsenfunktionsstörungen fanden sich keine signifikanten Änderungen der TBG-Spiegel, auch nicht bei direktem Vergleich zwischen Hyperthyreose (20,0±3,5 mg/l) und Hypothyreose (21,6±7,0 mg/l). Veränderte T4/TBG-Quotienten spiegeln bei diesen Erkrankungen folglich die von der Norm abweichende Schilddrüsenfunktion wider. Von diesen Schilddrüsenfunktionsstörungen lassen sich an Hand der normalen T4/TBG-Quotienten alle Zustände mit erhöhten bzw. erniedrigten Gesamt-T4-Spiegeln abgrenzen, die primär auf einer quantitativen Änderung der TBG-Spiegel beruhen

Absence of a dose-rate effect in the transformation of C3H 10T1/2 cells by α-particles

The findings of Hill et al. (1984) on the greatly enhanced transformation frequencies at very low dose rates of fission neutrons induced us to perform an analogous study with -particles at comparable dose rates. Transformation frequencies were determined with γ-rays at high dose rate (0·5 Gy/min), and with -particles at high (0·2 Gy/min) and at low dose rates (0·83-2·5 mGy/min) in the C3H 10T1/2 cell system. α-particles were substantially more effective than γ-rays, both for cell inactivation and for neoplastic transformation at high and low dose rates. The relative biological effectiveness (RBE) for cell inactivation and for neoplastic transformation was of similar magnitude, and ranged from about 3 at an -particle dose of 2 Gy to values of the order of 10 at 0·25 Gy. In contrast to the experiments of Hill et al. (1984) with fission neutrons, no increased transformation frequencies were observed when the -particle dose was protracted over several hours

Movement and ranging patterns of the Common Chaffinch in heterogeneous forest landscapes

The partitioning of production forests into discretely managed forest stands confronts animals with diversity in forest attributes at scales from point-level tree assemblages to distinct forest patches and range-level forest cover. We have investigated the movement and ranging patterns of male Common Chaffinches, Fringilla coelebs, in heterogeneous forest production landscapes during spring and summer in south-western Germany. We radio-tracked a total of 15 adult males, each for up to six days, recording locations at 10-min intervals. We then performed point-level tree surveys at all tracking locations and classified forest stand attributes for the areal covering of birds’ ranges. Movement distances were shortest in beech forest stands and longer in spruce-mixed and non-spruce conifer stands. Movement distances increased with stand age in beech stands but not in others, an effect that was only detectable in a multilevel hierarchical model. We found negligible effects of point-level tree assemblages and temperature on movement distances. Daily range estimates were from 0.01 to 8.0 hectare (median of 0.86 ha) with no evident impact of forest attributes on ranging patterns but considerable intra-individual variation in range sizes over consecutive days. Most daily ranges covered more than one forest stand type. Our results show that forest management impacts the movement behaviour of chaffinches in heterogeneous production forest. Although point-level effects of movement distances are weak compared with stand-level effects in this study, the hierarchical organization of forest is an important aspect to consider when analysing fine-scale movement and might exert more differentiated effects on bird species that are more sensitive to habitat changes than the chaffinch

Ultrathin Polydopamine Films with Phospholipid Nanodiscs Containing a Glycophorin A Domain

Cellular membranes have long served as an inspiration for nanomaterial research. The preparation of ultrathin polydopamine (PDA) films with integrated protein pores containing phospholipids and an embedded domain of a membrane protein glycophorin A as simplified cell membrane mimics is reported. Large area, ultrathin PDA films are obtained by electropolymerization on gold surfaces with 10–18 nm thickness and dimensions of up to 2.5 cm2. The films are transferred from gold to various other substrates such as nylon mesh, silicon, or substrates containing holes in the micrometer range, and they remain intact even after transfer. The novel transfer technique gives access to freestanding PDA films that remain stable even at the air interfaces with elastic moduli of ≈6–12 GPa, which are higher than any other PDA films reported before. As the PDA film thickness is within the range of cellular membranes, monodisperse protein nanopores, so-called “nanodiscs,” are integrated as functional entities. These nanodisc-containing PDA films can serve as semi-permeable films, in which the embedded pores control material transport. In the future, these simplified cell membrane mimics may offer structural investigations of the embedded membrane proteins to receive an improved understanding of protein-mediated transport processes in cellular membranes

Syrian hamster dermal cell immortalization is not enhanced by power line frequency electromagnetic field exposure

Several epidemiological studies have suggested associations between exposure to residential power line frequency electromagnetic fields and childhood leukaemia, and between occupational exposure and adult leukaemia. A variety of in vitro studies have provided limited supporting evidence for the role of such exposures in cancer induction in the form of acknowledged cellular end points, such as enhanced mutation rate and cell proliferation, though the former is seen only with extremely high flux density exposure or with co-exposure to ionizing radiation. However, in vitro experiments on a scale large enough to detect rare cancer-initiating events, such as primary cell immortalization following residential level exposures, have not thus far been reported. In this study, large cultures of primary Syrian hamster dermal cells were continuously exposed to power line frequency electromagnetic fields of 10 100 and 1000 μT for 60 h, with and without prior exposure to a threshold (1.5 Gy), or sub-threshold (0.5 Gy), immortalizing dose of ionizing radiation. Electromagnetic field exposure alone did not immortalize these cells at a detectable frequency (≥ 1 × 10−7); furthermore, such exposure did not enhance the frequency of ionizing radiation-induced immortalization. © 1999 Cancer Research Campaig

Dominant negative knockout of p53 abolishes ErbB2-dependent apoptosis and permits growth acceleration in human breast cancer cells

We previously reported that the ErbB2 oncoprotein prolongs and amplifies growth factor signalling by impairing ligand-dependent downregulation of hetero-oligomerised epidermal growth factor receptors. Here we show that treatment of A431 cells with different epidermal growth factor receptor ligands can cause growth inhibition to an extent paralleling ErbB2 tyrosine phosphorylation. To determine whether such growth inhibition signifies an interaction between the cell cycle machinery and ErbB2-dependent alterations of cell signalling kinetics, we used MCF7 breast cancer cells (which express wild-type p53) to create transient and stable ErbB2 transfectants (MCF7-B2). Compared with parental cells, MCF7-B2 cells are characterised by upregulation of p53, p21WAF and Myc, downregulation of Bcl2, and apoptosis. In contrast, MCF7-B2 cells co-transfected with dominant negative p53 (MCF7-B2/Δp53) exhibit reduced apoptosis and enhanced growth relative to both parental MCF7-B2 and control cells. These data imply that wild-type p53 limits survival of ErbB2-overexpressing breast cancer cells, and suggest that signals of varying length and/or intensity may evoke different cell outcomes depending upon the integrity of cell cycle control genes. We submit that acquisition of cell cycle control defects may play a permissive role in ErbB2 upregulation, and that the ErbB2 overexpression phenotype may in turn select for the survival of cells with p53 mutations or other tumour suppressor gene defects

Laser diode based THz-TDS system with 133 dB peak signal-to-noise ratio at 100 GHz

Abstract Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful and versatile tool in various scientific fields. These include—among others—imaging, material characterization, and layer thickness measurements. While THz-TDS has achieved significant success in research environments, the high cost and bulky nature of most systems have hindered widespread commercialization of this technology. Two primary factors contributing to the size and cost of these systems are the laser and the optical delay unit (ODU). Consequently, our group has focused on developing THz-TDS systems based on compact monolithic mode-locked laser diodes (MLLDs). The ultra-high repetition rate (UHRR) of the MLLD has the added benefit that it allows us to utilize shorter ODUs, thereby reducing the overall cost and size of our systems. However, achieving the necessary precision in the ODU to acquire accurate terahertz time-domain signals remains a crucial aspect. To address this issue, we have developed and enhanced an interferometric extension for UHRR-THz-TDS systems. This extension is inexpensive, compact, and easy to incorporate. In this article, we present the system setup, the extension itself, and the algorithmic procedure for reconstructing the delay axis based on the interferometric reference signal. We evaluate a dataset comprising 10,000 signal traces and report a standard deviation of the measured terahertz phase at 1.6 THz as low as 3 mrad. Additionally, we demonstrate a remaining peak-to-peak jitter of only 20 fs and a record-high peak signal-to-noise ratio of 133 dB at 100 GHz after averaging. The method presented in this paper allows for simplified THz-TDS system builds, reducing bulk and cost. As a result, it further facilitates the transition of terahertz technologies from laboratory to field applications