Showing papers by "Leibniz Association published in 1997"
TL;DR: The RA-induced accelerated expression of cardiac-specific genes results in an enhanced development of ventricular cardiomyocytes in pluripotent embryonic stem cells.
503 citations
TL;DR: A retinoic acid + db‐cAMP‐inducible embryonic stem cell model of in vitro vasculogenesis and ES cell‐derived cells expressing VSMC‐specific MHC and functional VSMC properties may be a suitable system to study mechanisms of VSMC differentiation.
Abstract: Vascular smooth muscle cell (VSMC) differentiation is important in understanding vascular disease; however, no in vitro model is available. Totipotent mouse embryonic stem (ES) cells were used to establish such a model. To test whether the ES cell-derived smooth muscle cells expressed VSMC-specific properties, the differentiated cells were characterized by 1) morphological analysis, 2) gene expression, 3) immunostaining for VSMC-specific proteins, 4) expression of characteristic VSMC ion channels, and 5) formation of [Ca2+]i transients in response to VSMC-specific agonists. Treatment of embryonic stem cell-derived embryoid bodies with retinoic acid and dibutyryl-cyclic adenosine monophosphate (db-cAMP) induced differentiation of spontaneously contracting cell clusters in 67% of embryoid bodies compared with 10% of untreated controls. The highest differentiation rate was observed when retinoic acid and db-cAMP were applied to the embryoid bodies between days 7 and 11 in combination with frequent changes of culture medium. Other protocols with retinoic acid and db-cAMP, as well as single or combined treatment with VEGF, ECGF, bFGF, aFGF, fibronectin, matrigel, or hypoxia did not influence the differentiation rate. Single-cell RT-PCR and sequencing of the PCR products identified myosin heavy chain (MHC) splice variants distinguishing between gut and VSMC isoforms. RT-PCR with VSMC-specific MHC primers and immunostaining confirmed the presence of VSMC transcripts and MHC protein. Furthermore, VSMC expressing MHC had typical ion channels and responded to specific agonists with an increased [Ca2+]i. Here we present a retinoic acid + db-cAMP-inducible embryonic stem cell model of in vitro vasculogenesis. ES cell-derived cells expressing VSMC-specific MHC and functional VSMC properties may be a suitable system to study mechanisms of VSMC differentiation.
251 citations
TL;DR: Sulfate-reducing bacteria from the oxic sediment layers revealed a higher oxygen tolerance and capacity of oxygen respiration than isolates from the anoxic sediment layers, but no sulfate reduction was observed in the presence of oxygen, since oxygen was preferentially reduced.
150 citations
TL;DR: Eggs of zebrafish exposed to microcystin-LR at concentrations of 0.5, 5 and 50 μg litre −1 from blastula stage up to the end of embryonic development showed decreased survival, and exposure with various aqueous cyanobacterial crude extracts from field samples and batch cultures retarded larval growth.
144 citations
TL;DR: Both translocation wheats deriving from the Weihenstephan (Munich) and from the Salzmunde (Halle/S.) origin showed an identical DNA fragment which was typical for the gene pool of Petkus rye, suggesting that both German sources have one progenitor in common.
Abstract: In order lo investigate the origin of two of the German 1RS. 1BL wheat-rye translocations used world-wide in breeding, a number of DNA probes were considered which (a) were critical for the short arm of the rye chromosome 1 R and (b) should show a specificity for the gene pool of Petkus rye. The DNA probe CDO580 was revealed as a specific one. (1) It clearly differentiated 1RS.1AL (‘Amigo’). 1RS.lBL (‘Salmon’) and 1RS.1DL (‘Gabo’) from the two German sources. (2) Both translocation wheats deriving from the Weihenstephan (Munich) and from the Salzmunde (Halle/S.) origin showed an identical DNA fragment which was typical for the gene pool of Petkus rye. It is supposed that both German sources have one progenitor in common.
117 citations
TL;DR: In this paper, the deformation and formation-of-texture processes can be explained by the model of solution-precipitation creep, where the main driving forces of deformation processes are the chemical potentials of the atomic species in the liquid phase or at the surfaces of the crystallites.
111 citations
TL;DR: In this article, the size distributions and hygroscopic growth spectra of aerosol particles were measured during the GCE cloud experiment at Great Dun Fell in the Pennine Hills in northern England.
96 citations
TL;DR: In this article, ground-based observations of the wind field in the mesosphere/lower thermosphere have been used to investigate long-lasting wind variations at mid-latitudes.
90 citations
TL;DR: A number of X chromosome DNA sequences have been isolated from a dioecious plant, Melandrium album, using chromosome microdissection followed by degenerate oligonucleotide-primed polymerase chain reaction (DOP–PCR) amplification.
Abstract: A number of X chromosome DNA sequences have been isolated from a dioecious plant, Melandrium album (syn. Silene latifolia), using chromosome microdissection followed by degenerate oligonucleotideprimed polymerase chain reaction (DOP-PCR) amplification. Six DNA clones were selected and further characterized by DNA/DNA hybridization techniques to check their copy numbers, sex-specific methylation patterns, species specificity and positions on chromosomes. These clones were moderately to highly repetitive (approximately 10(3)-10(5) copies per haploid genome) and none of them gave a positive signal on Northern blots. One of the clones yielded a sex-specific methylation pattern: its abundant non-methylated CCGG island was found only in males. All the clones also hybridized to two closely related dioecious Melandrium species (M. rubrum and M. dicline). Nucleotide sequences of two X-derived clones showed a number of internal short direct repeats; one of them strikingly resembled a plant conservative telomere sequence (TTTAGGG). None of the clones hybridized to the X chromosome only, but all were localized at the telomeric heterochromatic regions (DAPI C-bands) of both arms of a vast majority of M. album chromosomes using the fluorescence in situ hybridization (FISH) technique. However, the non-homologous arm of the Y chromosome (contrary to the arm homologous to the X chromosome, possessing the pseudoautosomal region) showed neither a DAPI C-banding-stained heterochromatin nor a FISH signal with any of the DNA probes tested, thus indicating its evolutionary diversification.
87 citations
TL;DR: A clearly definable upper tolerance limit for chromosome arm length has been found and it is postulate that, for normal development of an organism, the longest chromosome arm must not exceed half of the average length of the spindle axis at telophase.
86 citations
TL;DR: In this paper, a follow-up of cancer mortality for a cohort study of man-made vitreous fiber production workers from Denmark, Finland, Norway, Sweden, United Kingdom, Germany, and Italy, from 1982 to 1990, was presented.
Abstract: We have updated the follow-up of cancer mortality for a cohort study of man-made vitreous fiber production workers from Denmark, Finland, Norway, Sweden, United Kingdom, Germany, and Italy, from 1982 to 1990. In the mortality analysis, 22,002 production workers contributed 489,551 person-years, during which there were 4,521 deaths. Workers with less than 1 year of employment had an increased mortality [standardized mortality ratio (SMR) = 1.45; 95% confidence interval (CI) = 1.37-1.53]. Workers with 1 year or more of employment, contributing 65% of person-years, had an SMR of 1.05 (95% CI = 1.02-1.09). The SMR for lung cancer was 1.34 (95% CI = 1.08-1.63, 97 deaths) among rock/slag wool workers and 1.27 (95% CI = 1.07-1.50, 140 deaths) among glass wool workers. In the latter group, no increase was present when local mortality rates were used. Among rock/slag wool workers, the risk of lung cancer increased with time-since-first-employment and duration of employment. The trend in lung cancer mortality according to technologic phase at first employment was less marked than in the previous follow-up. We obtained similar results from a Poisson regression analysis limited to rock/slag wool workers. Five deaths from pleural mesothelioma were reported, which may not represent an excess. There was no apparent excess for other categories of neoplasm. Tobacco smoking and other factors linked to social class, as well as exposures in other industries, appear unlikely to explain the whole increase in lung cancer mortality among rock/slag wool workers. Limited data on other agents do not indicate an important role of asbestos, slag, or bitumen. These results are not sufficient to conclude that the increased lung cancer risk is the result of exposure to rock/slag wool; however, insofar as respirable fibers were an important component of the ambient pollution of the working environment, they may have contributed to the increased risk.
TL;DR: Leaves of barley treated with jasmonic acid, its methyl ester, or its amino acid conjugates exhibit up‐regulation of specific genes and down-regulation of house‐keeping genes.
TL;DR: In this article, a 3D molybdenum sulfide film with interlayers of Cr3Si or Cr were deposited onto steel substrates by means of rf magnetron sputtering.
TL;DR: In this paper, the formation and occurrence of new ultrafine aerosol particles were studied in association with an orographic cloud during a field experiment at Great Dun Fell (GDF), Northern England.
TL;DR: The Ground-based Cloud Experiment on Great Dun Fell as discussed by the authors used a wide range of measurements of trace gases, aerosol particles and cloud droplets at five sites to study their sources and sinks especially those in cloud.
TL;DR: In this paper, the shape of the tensiogram depends on both fibre surface and resins chemistry, and the slope of the force versus stage position plots represents the fibre/matrix interaction as swelling or acid base interaction and depends on stage speed and fibre roughness.
TL;DR: In this article, the amplified spontaneous emission is measured and spectrally resolved in both TE and TM polarisations; it is dependent on the current injected into the contact stripes of variable length on the laser structures.
Abstract: A new method for determining gain spectra is presented. The amplified spontaneous emission is measured and spectrally resolved in both TE and TM polarisations; it is dependent on the current injected into the contact stripes of variable length on the laser structures. The maximum gain and internal losses correspond well with the results of broad area lasers.
TL;DR: In this paper, a model of the aerosol size distribution upwind and downwind of the Great Dun Fell cap cloud was presented, along with measurements of sulphur dioxide, hydrogen peroxide and ozone.
TL;DR: In this article, size-dependent cloud droplet solute concentrations were measured using a two-stage fog water impactor at the summit station of Great Dun Fell (GDF) in the north of England.
TL;DR: In this article, a network-like structure of polypyrrole embedded in the insulating polymer matrix was determined by lowvoltage scanning electron microscopy, and the stability of PP/PPy composites was investigated by thermogravimetric analysis and by conductivity measurements during heating cooling cycles.
Abstract: Conducting polymer composites of polyethylene and polypyrrole (PE/ PPy), polypropylene and polypyrrole (PP/PPy) and poly(methyl methacrylate) and polypyrrole (PPMA/PPy) were prepared by means of a chemical modification method resulting in a network-like structure of polypyrrole embedded in the insulating polymer matrix. The content of polypyrrole determined by elemental analysis varied from 0.25 to 17wt%. Electrical conductivity of compression-moulded samples depended on the concentration of polypyrrole and reached values from 1 x 10 -11 to 1Scm -1 . The morphology of the composites and blends was studied by low-voltage scanning electron microscopy. The stability of PP/PPy composites was investigated by thermogravimetric analysis and by conductivity measurements during heating-cooling cycles. There was only a small drop in conductivity caused by the annealing of PP/PPy composites in air at temperatures up to 80°C. The results of thermogravimetric analysis showed a stabilizing effect of PPy on PMMA/PPy composites against thermal degradation. The antistatic properties of PMMA/PPy composites were demonstrated.
TL;DR: In this paper, the effects of war on the key economic variables capital, technology, uncertainty, and the government's fiscal deficit are discussed before proceeding to the analysis of individuals, firms and government.
Abstract: The aim of this paper is to analyse some macroeconomic channels operating in a war economy. At the theoretical level, the effects of such war on the key economic variables capital, technology, uncertainty, and the government's fiscal deficit are discussed before proceeding to the analysis of individuals, firms and the government. These elements are combined in a dynamic macroeconomic model to study a war's impact on output, growth, consumption, welfare and the national debt. The final section of this paper considers economic policy implications for a government at war, and for donors supporting a war economy. Both the theory and the evidence, drawn from Mozambique, suggest that while capital destruction is the most obvious cost of conflict the long-term development potential of a war economy is more severely damaged by increases in the fiscal deficit, uncertainty and transactions inefficiency. Furthermore, economic policies implemented during a war will determine the size and nature of the country's long-term peace dividend.
TL;DR: The data suggest that like in yeast, in plants a certain subfamily of UBC is specifically involved in the proteolytic degradation of abnormal proteins as result of stress.
TL;DR: In this article, a microstructure-dependent anisotropic infrared-optical dielectric function model for mixed-phase polycrystalline material was proposed to derive the transverse and longitudinal optical modes observable in thin films.
Abstract: We present a microstructure-dependent anisotropic infrared-optical dielectric function model for mixed-phase polycrystalline material from which we derive the transverse and longitudinal-optical modes observable in thin films. Infrared ellipsometry over the wavelength range from 700 to $3000{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ is then used to determine the phase and microstructure of polycrystalline and multilayered hexagonal and cubic boron nitride thin films deposited by magnetron sputtering onto (100) silicon. The ellipsometric data depend on the thin-film multilayer structure, the layer-phase composition, and the average orientation of the hexagonal grain $c$ axes. In particular, we demonstrate the existence of spectral shifts of longitudinal optical phonons as a function of microstructure, i.e., the average grain crystallographic orientation within the mixed-phase material.
TL;DR: In this paper, a self-consistent comparison of axissymmetric and 3-dimensional simulations of the tropospheric circulation under idealized physical conditions is presented, revealing a feedback of transient eddies onto the Hadley circulation which, first, strongly depends on equatorial heating and, second, is in case of realistic heating quite different from prescribed eddy forcing.
Abstract: We present self-consistent comparisons of axissymmetric and 3-dimensional simulations of the tropospheric circulation under idealized physical conditions. These reveal a feedback of transient eddies onto the Hadley circulation which, first, strongly depends on equatorial heating and, second, is in case of realistic heating quite different from prescribed eddy forcing. A quantitative estimation for the eddy-induced mixing of vorticity into the poleward flow of the Hadley cell is given. The proposed relation is in accordance with observations. It is derived from the computational result that eddy momentum flux convergence is of the same order as the equatorward flux of relative vorticity generated by the Hadley circulation. Evaluation of the local budgets of sensible heat gives rise to a clear picture of how the poleward heat transports due to Hadley circulation and transient eddies interlock. This mechanism is found to be essential for an interpretation of the eddy feedback.
TL;DR: It is suggested that JIP60 perturbs the translation machinery in planta with an increased polysome/monosome ratio but a decreased in-vivo translation activity.
Abstract: In this paper we report the in-planta activity of the ribosome-inactivating protein JIP60, a 60-kDa jasmonate-induced protein from barley (Hordeum vulgare L.), in transgenic tobacco (Nicotiana tabacum L.) plants. All plants expressing the complete JIP60 cDNA under the control of the cauliflower mosaic virus (CaMV) 35S promoter exhibited conspicuous and similar phenotypic alterations, such as slower growth, shorter internodes, lanceolate leaves, reduced root development, and premature senescence of leaves. Microscopic inspection of developing leaves showed a loss of residual meristems and higher degree of vacuolation of mesophyll cells as compared to the wild type. When probed with an antiserum which was immunoreactive against both the N- and the C-terminal half of JIP60, a polypeptide with a molecular mass of about 30 kDa, most probably a processed JIP60 product, could be detected. Phenotypic alterations could be correlated with the differences in the detectable amount of the JIP60 mRNA and processed JIP60 protein. The protein biosynthesis of the transformants was characterized by an increased polysome/monosome ratio but a decreased in-vivo translation activity. These findings suggest that JIP60 perturbs the translation machinery in planta. An immunohistological analysis using the JIP60 antiserum indicated that the immunoreactive polypeptide(s) are located mainly in the nucleus of transgenic tobacco leaf cells and to a minor extent in the cytoplasm.
TL;DR: Spearman rank correlations between fish abundance and type of embankment revealed that perch showed a statistically significant numerical dominance in waterways consisting predominately of an artificial shoreline, suggesting thatPerch may be used as an indicator of the structural degradation of watercourses.
Abstract: — Simple morphological characteristics and fish assemblage data were collected in representative numbers from 12 inland waterways in the northeastern lowlands of Germany between 1992 and 1995. Fish abundance data were pooled and classified into three main groups: perch Perca fluviatilis (L.), roach Rutilus rutilus (L.) and other species. Spearman rank correlations between fish abundance and type of embankment revealed that perch showed a statistically significant numerical dominance in waterways consisting predominately of an artificial shoreline, suggesting that perch may be used as an indicator of the structural degradation of watercourses.
Journal Article•
TL;DR: The reproductive competence of oocytes collected post mortem was demonstrated by development to embryos (> or = 8 cells) in vitro and the results demonstrate the possibility of retrospective assessment of male and female reproductive capacity.
Abstract: Methods for rescuing oocytes and spermatozoa post mortem are described, which were adapted from domestic cat as a model. Ovaries were mechanically processed for large-scale recovery of oocytes. Numbers of intact cumulus-oocyte complexes (COCs) per animal and of preantral follicles per ovary were 18 +/- 2 and 2892 +/- 665 in domestic cats, respectively. Similar results were obtained from 13 individuals of 6 nondomestic felids: 16 +/- 2 COCs and 1867 +/- 1144 follicles. Preantral follicles were cultured for at least 7 days. Intact COCs were maturated for 24 h and fertilized in vitro with homologous or heterologous (from domestic cat) spermatozoa. Spermatozoa were collected from caudae epididymides (n = 11; five nondomestic species) and cryopreserved (n = 8) using a programmed freezer. The reproductive competence of oocytes collected post mortem was demonstrated by development to embryos (> or = 8 cells) in vitro. Spermatogenic efficiency of males was assessed by flow cytometric analysis of mitotic and meiotic testicular cells as well as by estimation of testosterone concentration in testes. The results demonstrate the possibility of retrospective assessment of male and female reproductive capacity. In conclusion, the described methods could be a useful part of gamete rescue programmes for endangered felids.
TL;DR: Investigation of leaves of Melicope ptelefolia afforded 18 2,2-dimethyl-2H-1-benzopyrans, consisting of 14 new members, including one benzodipyran and four known compounds, which were established by mass and NMR spectroscopy, especially NOE and HMBC experiments.
TL;DR: In this article, an artificial calcite precipitation was induced by hypolimnetic injection of CaO in enclosures during the summer stagnation of the Dagowsee, a stratified eutrophic hardwater lake.
TL;DR: Using polyclonal antibodies directed against acetylated isoforms of histone H4, indirect immunofluorescence revealed hyperacetylation for all H4 variants at the nucleolus organizer region of metaphase chromosomes of the field bean Vicia faba, which represents a hitherto unique switch of hist one acetylation pattern during the cell cycle.
Abstract: Using polyclonal antibodies directed against acetylated isoforms of histone H4 (H4 acetylated at lysine positions 5, 8, 12, 16 and H4 tetraacetylated), indirect immunofluorescence revealed hyperacetylation for all H4 variants at the nucleolus organizer region (NOR) of metaphase chromosomes of the field bean Vicia faba. The transcriptionally inactive and late-replicating heterochromatin regions proved to be hypoacetylated at lysine positions 5, 8 and 12. The remaining chromatin showed average fluorescence. These patterns were altered when deacetylase was blocked by exposure of root tip meristems to trichostatin A for more than 2 h prior to fixation. Under these conditions, all lysine positions, except lysine 8, appeared to be hyperacetylated at the NOR and in addition at the prominent heterochromatin domains. This observation represents a hitherto unique switch of histone acetylation pattern during the cell cycle. This is apparently caused by deposition of acetylated H4.Ac5, 12 and 16 or by acetylation directly after replication, which later on becomes reduced (H4.Ac16) or even reversed (H4.Ac5 and 12) by deacetylase before cells enter mitosis.