Diurnal and seasonal variation of the equilibrium state between short-lived radon decay products and radon gas in ground-level air

To study seasonal and diurnal variations and the effect of meteorological parameters, the equilibrium factor F (i.e. the ratio of equilibrium equivalent radon daughter concentration and radon gas concentration) was determined as a result of measurements on a test field at Munich-Neuherberg, Germany, continuously from October 1995 through March 1997. On average, F was found to be 0.62±0.09 (95% confidence level). The time series of F showed no distinct seasonal variations. Nevertheless, typical diurnal variations as well as seasonal variations of the diurnal behaviour were observed. Generally, F was found to be increased in the early afternoon, i.e. under conditions of enhanced vertical mixing in the atmosphere. The daily differences between high and low values of F depended on the season. On average, low F values were characteristic for days with precipitation and high wind speed, i.e. under turbulent atmospheric conditions. Therefore, taking daily mean values into account, F was found to be positively correlated with the aerosol concentration, although a relationship between the diurnal behaviour of the aerosol concentration and that of F was not detectable. Received: 6 September 2000 / Accepted: 20 February 2001     

A new method for radioautographic observation on isolated cells

Summary The procedure of a new method of radioautographic observation on isolated cells from the liver and the pancreas was described. Through this method binucleato cells are distinctly distinguished from mononucleate cells in radioautographs. Thus, the study on binuclearity in such organs from histochemical viewpoint has come to be carried out without difficulty.

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Zusammenfassung Eine neue Methode für radioautographische Beobachtung über die isolierten Zellen einiger Organe wurde dargestellt. Durch diese Methode kann man leicht zweikernigen Zellen von einkernigen in solchen Organen wie der Leber oder dem Pankreas, die häufig zweikernige Zellen haben, auf radioautographischen Präparaten unterscheiden. Dadurch kann man ohne Schwierigkeit über die Zweikernigkeit aus dem histochemischen Standpunkt studieren.

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With 5 Figures in the Text     

In vitro exposure of mammalian cells to radon: dosimetric considerations

We have developed a model to calculate the dose to the cell nucleus in cells exposed in suspension to radon and/or radon progeny. The model addresses the influence of (1) different radiation qualities and energies in the irradiation milieu; (2) the contribution to dose from radioactivity in the medium surrounding the cell after exposure to the radon gas as well as that from excess radon progeny associated with the cell; (3) the geometry of the cell and of the radiosensitive target, the cell nucleus; (4) the intracellular localization of the radionuclides; (5) attenuation of the alpha particles by the cytoplasm; (6) the radionuclide concentrations in the medium; and (7) the length of exposure. Investigation of the influence of these various parameters was made using an irradiation system in which cells were exposed to 212Bi, which decays to stability with the emission of an alpha particle (either 6.05 or 8.78 MeV). The information from these studies was then used to develop the system further for more complex systems in which 222Rn and its progeny are present. The model takes into account the contribution of dose from different radiation sources using scintillation counts of the medium and the cells, and it is useful for calculations of dose in situations where cells are exposed in suspension culture.     

A new method for the three-dimensional in vitro growth of human cancer cells

A method has been developed which allows, for the first time, the in vitro growth of human tumor cells in calcium alginate gel microcapsules. The three-dimensional matrix is permeable to macromolecules of at least 200 000 molecular weight (MW) (e.g., carcinoembryonic antigen) and provides an environment for organized growth and differentiation more comparable to in vivo growth than monolayer culture. This inexpensive, nondestructive procedure allows studies of morphological, biochemical and immunochemical parameters of human tumor cells within a single model.     

Pharmacological in vitro evaluation of new substance P-cyclodextrin derivatives designed to drug targeting towards NK1-receptor bearing cells.

Some biological properties of new bifunctional conjugates designed for drug targeting were evaluated through in vitro experiments. Eight peptidylcyclodextrin compounds were used, which correspond to modified beta- or gamma-cyclodextrin (CD) grafted on neuropeptide substance P (SP) or a shorter derivative (SP(4-11)). Using anti-SP and anti-CD antibodies as molecular probes, we showed that the main structural features of the two moieties of these adducts were preserved. Binding experiments, using CHO cells expressing the human SP-specific NK1 receptor, demonstrated the functionality of all peptidylcyclodextrin derivatives, which exhibited IC50 values in a 10(-9)-10(-7) M range. All compounds were able to induce a pharmacological response, triggering phosphatidylinositol turnover with EC50 values in the same range as the natural ligand. Moreover, autoradiography analysis of rat spinal corn sections proved that [125I]SP binding was dose-dependently displaced by one selected compound (a gamma-CD-SP), showing a similar affinity of this adduct for the rat neurokinin 1 receptor. Our observations demonstrate that these peptidylcyclodextrins efficiently target NK1 receptor-expressing cells.     

A retro-inverso TAT-like peptide designed to deliver cysteamine to cells

A retro-inverso, TAT-like peptide wherein lysine residues are replaced with cysteine residues bearing a disulfide-linked cysteamine group is found to engage in thiol–disulfide exchange with cysteine. These peptides are transported into cells and localize to lysosomes. Cellular uptake is enhanced in peptides bearing two cysteamine groups over those with one or none, by factors of approximately 1.5 and 12, respectively.     

A new method for the analysis of sums of exponential decay curves

A method based on Fourier Transform is presented for the representation of data by an arbitrary sum of exponentials or Gaussian functions. The method has been successfully applied to the type of data sets which arise in pharmacokinetic studies. Two techniques for error ripple elinination are discussed.     

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration

Seasonal and long-term variation of the airborne ²¹²Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EEC_Rn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m^–3, while daily mean concentrations varied from ≤0.01 to 0.34 Bq m^–3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concen-tration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EEC_Rn222) of 8.4 Bq m^–3 measured for this location in the same period. In most years the seasonal pattern of ²¹²Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived ²²²Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of ²¹²Pb is the extremely reduced flux of thoron gas from the ground during the winter months. Received: 19 August 1997 / Accepted in revised form: 22 January 1998     

A new method to express embryotoxic data obtained in vitro on whole murine embryos

This report proposes to express the effect of drugs in the whole embryo culture system by a new method using an intrinsic reference. Percentages of malformed embryos or other defects in development, expressed as percentages of controls, are plotted against concentrations of the drug expressed as percentages of the concentration inducing 50% embryolethality (ELC50). It is suggested that the slope generated by this method is directly related to the intensity of the in vitro teratogenic potential of the agent and allows an estimation of the specific interference with developmental processes. The method has been applied to data obtained from the literature and pertaining to 22 drugs. The slope generated by these drugs varied widely. The effect of these drugs could be meaningfully compared in spite of the wide range of ELC50 displayed by the drugs. In addition, results obtained for two drugs in different laboratories using different methods and species were in fair agreement when they were compared by using the proposed method. Finally, it is suggested that the method provides an improved means to inquire if there is any relevance of in vitro data to teratological results obtained in vivo.     

Reaction of chloroacetyl-CoA with rabbit fatty acid synthase: A new method to label specifically and quantify pantetheine prosthetic groups

The substrate analogue chloroacetyl-CoA inhibits fatty acid synthase by reacting with the ‘central’ or pantetheine thiol and not the ‘peripheral’ or β-ketoacylsynthase thiol as previously reported. This was demonstrated by the isolation of [¹⁴C]carboxymethylcysteamine after acid hydrolysis of enzyme labelled with chloro[¹⁴C]acetyl-CoA, and by the demonstration that more than one of the partial reactions is inhibited. This reagent now represents a simple and convenient tool both for quantification of the pantetheine thiol and for labelling this site for peptide mapping and isolation.     

A method to obtain avian germ-line chimaeras using isolated primordial germ cells.

Primordial germ cells (PGCs), collected from the blood of 2-day-old chick embryos, were concentrated by Ficoll density centrifugation. The blood contained 0.048% PGCs and the concentrated fraction contained 3.9% PGCs in blood cells. The PGCs were picked up with a fine glass pipette, and one hundred were then injected into the terminal sinuses of 2-day-old Japanese quail embryos (24 somites); bubbles were then inserted to prevent haemorrhage. The embryos were further incubated at 38 degrees C for 24 h, and then fixed. Serial sections were stained with the periodic acid-Schiff reagent (PAS) to demonstrate chicken PGCs and with Feulgen stain to identify quail cells. On the basis of the differences in staining properties, 63.6 +/- 5.3 chick PGCs were detected in the quail embryo in the area where the gonads develop. Furthermore, 39.3 +/- 4.5 chick PGCs were incorporated into the quail germinal epithelium within 24 h of the injection. A similar percentage of the host (quail) PGCs had also migrated to the germinal epithelium at the same stage of development. This technique for obtaining germ-line chimaeras will facilitate research on avian germ-line differentiation.     

Mutagenicity of methylisocyanate and its reaction products to cultured mammalian cells

Methylisocyanate (MIC) induced mutagenic responses in the absence of exogenous activation in the mouse lymphoma cell forward mutation assay at concentrations as low as 8-24 microM. MIC produced predominantly small mutant colonies, suggesting the possibility of clastogenic activity. The intermediate hydrolysis product, methylamine, was also mutagenic without exogenous activation but required several hundred-fold higher concentrations (ca. 3 mM). N,N'-Dimethylurea, the final product in the reaction of methylisocyanate and water, was totally refractory in either the presence or absence of S9 for concentrations up to 57 mM (5 mg/ml). The ethyl ester of N-methylcarbamic acid was also tested since it was the only available analogue to the highly reactive N-methylcarbamic acid intermediate. This compound was mutagenic only in the presence of S9 at doses exceeding 5-40 microM, which suggested the possibility that the free acid, produced by enzymatic hydrolysis, is also mutagenic. The mutagenic activity of the ester resulted solely in the production of small mutant colonies.     

Conditional expression and signaling of a specifically designed Gi-coupled receptor in transgenic mice

To control G protein signaling in vivo, we have modified G protein-coupled receptors to respond exclusively to synthetic small molecule agonists and not to their natural agonist(s). These engineered receptors are designated RASSLs (receptor activated solely by a synthetic ligand). A prototype RASSL (Ro1) based on the Gi-coupled K opioid receptor was expressed in transgenic mice under the control of the tetracycline transactivator (tet) system. Activation of Ro1 expressed in the heart decreased heart rate by up to 80%, an expected effect of increased Gi signaling. Maximal heart rate changes occurred in less than 1 min, demonstrating the speed of this inducible signaling system. This Ro1-mediated slowing of heart rate was also subject to desensitization, which lasted more than 24 h. Both the initial effect on heart rate and the desensitization occurred, even though Ro1 is derived from a human opioid receptor not normally involved in heart rate control. In addition, the tet system was used to induce Ro1 expression in hepatocytes and salivary gland, where Gi signaling is known to control physiologic events such as proliferation and secretion. These studies demonstrate that a RASSL can be inducibly expressed in several mouse tissues and used in vivo to activate G protein signaling in a controllable fashion.     

Eotaxin is specifically cleaved by hookworm metalloproteases preventing its action in vitro and in vivo

Eotaxin is a potent eosinophil chemoattractant that acts selectively through CCR3, which is expressed on eosinophils, basophils, mast cells, and Th2-type T cells. This arm of the immune system is believed to have evolved to control helminthic parasites. We hypothesized that helminths may employ mechanisms to inhibit eosinophil recruitment, to prolong worm survival in the host. We observed that the excretory/secretory products of the hookworm Necator americanus inhibited eosinophil recruitment in vivo in response to eotaxin, but not leukotriene B(4), a phenomenon that could be prevented by the addition of protease inhibitors. Using Western blotting, N. americanus supernatant was shown to cause rapid proteolysis of eotaxin, but not IL-8 or eotaxin-2. N. americanus homogenate was fractionated by gel filtration chromatography, and a FACS-based bioassay measured the ability of each fraction to inhibit the activity of a variety of chemokines. This resulted in two peaks of eotaxin-degrading activity, corresponding to approximately 15 and 50 kDa molecular mass. This activity was specific for eotaxin, as responses to other agonists tested were unaffected. Proteolysis of eotaxin was prevented by EDTA and phenanthroline, indicating that metalloprotease activity was involved. Production of enzymes inactivating eotaxin may be a strategy employed by helminths to prevent recruitment and activation of eosinophils at the site of infection. As such this represents a novel mechanism of regulation of chemokine function in vivo. The existence of CCR3 ligands other than eotaxin (e.g., eotaxin-2) may reflect the evolution of host counter measures to parasite defense systems.     

1,25-Dihydroxyvitamin D3 binds specifically to rat vascular smooth muscle cells and stimulates their proliferation in vitro

Cultured vascular smooth muscle cells (VSMC) derived from rat aorta were found to contain a specific receptor for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Its Kd (5.0 x 10(-11) M) and capacity (22.9 fmol/mg of cytosol protein) for 1,25-(OH)2D3, its sedimentation coefficient on a sucrose density gradient (3.2 S), its relative affinities for various vitamin D3 metabolites [1,25-(OH)2D3 greater than 25-hydroxyvitamin D3 greater than 24,25-dihydroxyvitamin D3 greater than vitamin D3] and its affinity for DNA-cellulose were similar to those reported for the 1,25-(OH)2D3 receptor in other tissues. 1,25-(OH)2D3 at concentrations of more than 10(-10) M caused dose-dependent enhancement of the proliferation of VSMC in DMEM with 10% FCS. 25-Hydroxyvitamin D3 stimulated the proliferation of VSMC only at its highest concentration tested (10(-6) M). These data show that 1,25-(OH)2D3 stimulates the proliferation of VSMC after its binding to a cytoplasmic receptor of the cells in vitro, and support the possibility that VSMC are target cells of the hormone.