Showing papers by "Free University of Berlin published in 1973"

Axioms for euclidean green's functions

Abstract: We give new (necessary and) sufficient conditions for Euclidean Green's functions to have analytic continuations to a relativistic field theory. These results extend and correct a previous paper.

The morphology of various types of cell death in prenatal tissues

Abstract: The morphology of physiological cell death and of necroses caused by treatment with various embryotoxic substances (cyclophosphamide, actinomycin D, vitamin A, vincristine, 6-aminonicotinamide, 6-mercaptopurine) and Mg deficiency were studied electron microscopically in rat and mouse embryos and fetuses. Three types of necroses were distinguished in control tissues. (1) Condensation and fragmentation of single cells undergoing phagocytosis, with lysosomal disintegration of the fragments in neighboring cells. (2) Primary formation of lysosomes in dying cells, with activation and subsequent destruction and phagocytosis of the fragments by neighboring cells. This type of cell death in most instances was found during destruction of organs and large cell units. (3) Disintegration of cells into fragments, which were optically no longer detectable, without involvement of the lysosomal system, e.g., in embryonic and epiphyseal cartilage before ossification. In cases of embryolethal toxic agents, e.g., Mg deficiency, cell necroses of large areas prevailed, which were characterized by typical pyknoses (rough, dense chromatin) and lack of lysosomes. In the case of teratogenic effects, however, substances that disturb replication, transcription, and translation (cyclophosphamide, actinomycin D, 6-mercaptopurine) caused an increase in the number of necroses of type 1. It can, therefore, be assumed that under these conditions similar processes take place in physiological and experimentally induced necroses. After administration of vitamin A, labilization of lysosomes and necroses of type 2 were observed.

Moses Mendelssohn;: A biographical study

Abstract: Preface 1 Years of Growth Childhood in Dessau * Early Years in Berlin * The Budding Philosopher * Lessing * The Metaphysician * The Bel Esprit * A Learned Society * Kohelet Mussar 2 Maturity and Fame Marriage and Family Life * Thomas Abbt * The Prize-Essay * The Correspondence about the Vocation of Man * The Phaedon * Questions and Answers * Cognate Hebrew Writings 3 Turning Point: The Lavater Affair 'Juif de Berlin' * The Prehistory of the Lavater Affair * Lavater's Challenge and Mendelssohn's Reply * First Reactions and Behind-the-Scene Activities Lavater's Reply and Mendelssohn's Epilogue * Reverberations of the Conflict * Literary Concerns and Another Lavater Episode 4 Changes in the Pattern of Life The Strange Illness * Ups and Downs A Chronicle of Events * Hebraica and Judaica * The Chronicle Continued * Some Philosophical Preoccupations * Friends in Unexpected Quarters 5 The Teacher The Avant-Garde of Haskala * The German Translation of the Pentateuch * Obstacles on the Road * Completing the Work 6 Political Reformer Spokesman of his People * Co-operation with Dohm * A Momentous Event and a New Tract for the Times * The Issue of Educational Reform * The Summer of 1782 * Jerusalem 7 Strains and Stresses Friendship with Lessing: The Last Phase * A Projected Essay on Lessing's Character * Jacobi's Attitude toward Mendelssohn: Antecedents of their Conflict * An Uneasy Correspondence 8 Guardian of the Enlightenment The Contest * Literary Activity, 1783-1785 * Morning Hours * In Combat * The Social and Domestic Scene * The End * Epilogue Notes Index of Subjects and Names

Molting hormone content, cuticle growth and gastrolith growth in the molt cycle of the crayfishOrconectes limosus

Abstract: The molting hormone titer during the course of the molt cycle of the crayfish has been determined using an improved extraction procedure. A slight increase of titer is apparent with the transition from stage C (0.29 ng/g) to Do (0.84 ng/g) when formation of the gastroliths starts. A further increase up to 1.9 ng/g occurs in D1. A steep, significant increase in hormone content was observed in transition to D2 when the formation of the new exocuticle commences, the value in D2 being 56.9 ng/g. The hormone content is only slightly lower in D3 (39.1 ng/g) when the exocuticle continues to be secreted. A sharp decrease is already observable before ecdysis, in D4 (9.5 ng/g). The values continue to decrease through stages A (0.84 ng/g) and B (0.29 ng/g), with gastroliths being resorbed. Cuticle growth, however, continues. Thus it is apparent that there are two phases of cuticle growth, a preecdysial phase which is hormone dependent and a postecdysial phase which seems to be independent of ecdysones.

Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. I. Target cells and possible mode of action.

Abstract: The effect of dextran sulfate on [3H]dThd incorporation in lymphoid cells was investigated. The polyanion activated DNA synthesis in spleen and bone marrow cells of normal mice. The highest rate of activation was detected in spleen cells of athymic (nude) mice; the ratio of [3H]dThd incorporation was higher in TxBM spleen cells of thymectomized, lethally irradiated and bone marrow protected mice than in spleen cells of normal donors. Thymus cells of normal mice could not be stimulated, but a slight response was obtained in cortisone-resistant thymus cells. A synergetic effect was found in normal thymus cells using a combination of dextran sulfate and phytohemagglutinin (PHA). In contrast, lipopolysaccharide and PHA showed no synergetic effect. The possible mode of action of polyanions as de-repressors of DNA synthesis is discussed.

Spin-dependent tunnelling from transition-metal ferromagnets

Abstract: Spin-dependent tunnelling from ferromanmetic Ni, Co, and Fe, is theoretically examined and it is shown that the tunnelling current is predominantly due to s electrons, despite the much greater density of d states in these metals s-d hybridization leads to a positive (parallel to the majority d electrons) polarization within ordinary Stoner (Hartree-Fock) theory, and it was found that lt was insufficient to explain the experiment However, if the self- energy due to spin-wave emission is included, good agreement with experiment for reasonable parameters was obtained Hence, it is concluded that the band- theoretical description of the magnetism of these metals is compatible with the recent experiments of Tedrow and Meservery, provided that the dominant many-body effects are properly taken into account (auth)

Grad und lokaler Zusammenhang in endlichen Graphen

Abstract: In der vorliegenden Note wird gezeigt, dab jeder endliche Graph G (mit mindestens einer Kante) zwei benachbarte Ecken x und y enth~ilt, die durch min {y(x, G), ?(y, G)} disjunkte Wege verbunden sind, wobei y(z, G) den Grad der Ecke z in G bedeute 1. Dies verschlirft Satz 1 aus [1] und l/iBt sich leicht mit der gleichen, dort entwickelten Methode beweisen. Ich iibernehme deshalb Terminologie und Bezeichnungen aus [-1 ], wiederhole aber (ohne Beweis) das entscheidende Lemma. Wir betrachten Tripel (G, V m, A), wobei der Teilgraph V,~ des Graphen G ein vollst~indiger Graph mi tm Ecken ist und A ~_ K(G) K(Vm) gilt. Ein solches Tripel nennen wir zuliissig, wenn die beiden folgenden Bedingungen erfiillt sind: a) Jede Kante aus A hat (genau) einen Endpunkt in I'm. b) Die Ecken yon Fm lassen sich so durchnumerieren, etwa E(Vm) = {el . . . . . era}, daft gilt: Wenn die Kante [%0, x] zu A gehiirt, dann gilt [%, x] ~ K(G) A j~r alle It mit 1 ~ It < Ito.

Triazenes, a new group of indirect mutagens. Comparative investigations of the genetic effects of different Aryldialkyltriazenes using Saccharomyces cerevisiae, the host-mediated assay, Drosophila melanogaster, and human chromosomes in vitro.

Abstract: Four genetic test systems were compared based on the activation of “indirect” mutagens in each. Three aryldialkyltriazenes were tested: 1-phenyl-3,3-dimethyltriazene (PDT), 1-(pyridyl-3)-3,3-dimethyltriazene (PyDT), and 1-(pyridyl-3- N -oxide)-3,3-dimethyltriazene (PyNDT). In the first system mitotic gene conversion was observed in Saccharomyces cerevisiae . Secondly, the host-mediated assay (HMA) was set up using the mouse and Saccharomyces. In Drosophila melanogaster various genetic abnormalities including X-linked recessive lethals, 2–3 translocations, complete loss of the X- or Y-chromosome, and partial loss of the Y were analysed after treatment. Finally, chromosome aberrations were determined in human leukocytes cultured in vitro . 1. (1) Some evidence that only PyDT and PyNDT can be designated as “indirect” mutagens was obtained. PDT, on the other hand, also seems to act as a “direct” mutagen. 2. (2) The relative genetic activity of the triazenes in the different test systems can be summarized as follows: Saccharomyces: PDT > PyDT (PyNDT no effect) HMA: PyDT ⋍ PyNDT > PDT Drosophila: PDT > PyNDT > PyDT Human chromosomes: PDT ⋍ PyDT ⋍ PyNDT (questionable effects) 3. (3) PDT and PyNDT induced recessive lethals and chromosome aberrations in the male germ cells of Drosophila. These genetic changes were observed in comparable frequencies for both chemicals. However, PyNDT was quite ineffective in causing dominant lethals, whereas PDT showed strong activity in this test. This suggests that the dominant lethals produced by PDT hardly can be due to chromosome breakage. The activity of PDT in producing dominant lethals is thought to result from highly cytotoxic properties of PDT. 4. (4) In the in vitro test with human chromosomes the triazenes showed very weak dose-independent effects. These data suggest that potent “indirect” mutagens of the triazene type cannot be recognized in this test system.

Theory for superconductivity in Pd-H and Pd-D systems

Abstract: A theory is presented explaining the recently observed superconductivity at 9 °K in Pd-H and at 11 °K in Pd-D as due to the quenching of the spin-fluctuations and as due to the decrease of the Coulomb pseudo-potential μ present in Pd. That one observes for PdD a larger superconducting transition temperatureT c than for PdH is explained by the larger lattice expansion resulting for adding H to Pd. The observed non-monotonic dependence ofT c on the Hydrogen concentration is explained by the fact that approximately λ ∝N(0) for smallN(0), whereN(0) is the electronic density of states at the Fermi-energy and where λ denotes the electron-phonon coupling constant. Superconducting transition temperatures are estimated for PtH and RhH.

Comment on the Absence of Radiative Corrections to the Anomaly of the Axial-Vector Current

Abstract: The absence of radiative corrections to the Schwinger-Bell-Jackiw-Adler anomaly of the axial-vector-current Ward-Takahashi identity is demonstrated using normal-product methods.

Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. II. Relationship between adjuvant activity and stimulation of DNA synthesis by polyanions.

Abstract: The effect of eleven different polyanions, among them dextran sulfate, and of two different preparations of dextran was investigated on [3H]dThd incorporation in spleen cells in vitro, and on PFC response to SRBC in vivo. In general, polyanions stimulated DNA synthesis in spleen cells and enhanced PFC response to SRBC. Dextran itself had no effect on DNA synthesis and on PFC response. The degree of activation of DNA synthesis by polyanions in vitro was found to correlate with the adjuvant activity of the substances in vivo It is postulated that activation of DNA synthesis in lymphoid cells is essential for the adjuvant activity of polyanions.

Mechanism of action of aldosterone on potassium transfer in the rat kidney.

Abstract: Electrophysiological studies were performed in proximal and distal tubules of rat kidneys. To assess the relative potassium permeability the tubular lumen was perfused with solutions of varying K concentrations while the transepithelial PD were measured. In the distal tubule the transport number for potassium was 0.43 in control rats and 0.27 in adrenal insufficiency. Acute (5 μg/100 g B.W.) or chronic (30 μg/100 g B.W. daily for 3 days) aldosterone administration normalized the relative permeability. This effect of aldosterone could not be prevented by cycloheximide (100 μg/100 g B.W.). The peritubular membrane potential of the distal tubule decreased from 75 mV in control rats to 62 mV in adrenalectomized rats. Acute injection of aldosterone had no effect on peritubular membrane potential. In the proximal tubule qualitatively similar results were obtained as in the distal tubule. The impairment of potassium secretion in adrenal insufficiency is at least partly due to a reduced permeability of the luminal membrane of the distale tubule. Aldosterone acutely stimulates potassium secretion by increasing the luminal permeability of the distal tubule. In comparison to the effect of aldosterone on active transport components the increase in luminal potassium permeability by aldosterone may be either less sensitive to blockade by inhibitors of protein synthesis or is not dependent upon induction of newly synthetized proteins.

Three-dimensional surface representation of the cilia-free nasal mucosa of man. A scanning-electron-microscopical study.

Abstract: The normal and the pathologically changed surface of the human nasal mucosa of the inferior conchae is described three-dimensionally with the aid of the scanning-electron-microscope Stereoscan. Scanning-electron-microscopical surface criteria are elaborated for differentiation of beaker cells, cilia-free cylindrical cells and squamous epithelial cells as well as for microvilli and re-proliferating kino-ciliae. The crossing effect of different-levelled cell borders and the appearance of different-levelled cell nuclei are typical of the squamous epithelium; they are not present in the cylindrical epithelium. The filled beaker cell shows a more homogeneous surface with small oval depressions and when compared with the surface of cilia-free cylindrical epithelial cells it presents a distinct decrease of microvilli-infestation. The microvilli show a ledge-like structure pattern whereas re-proliferating kinociliae have papilliform, bud-like cytoplasmic bulges. In pathologically changed nasal mucosa, dome-shaped...

Correlation between rate of cell division and loss of embryogenesis in longterm tissue cultures

Abstract: In experiments with carrot tissue cultures of different ages (up to 5 years) it was investigated whether relations exist between embryogenesisin vitro and certain growth parameters of the cultures. The normal pattern of embryo-formation on an inductive medium (Ms), with a maximum 20 weeks after the isolation of the cultures and its disappearance after about 60 weeks, could be changed by retardation of growth either by low temperatures or by culture on a non-inductive medium (Mw). In both cases partial inhibition of growth resulted in a prolonged period of competence of the cultures for embryo-formation. It was also found that a close relation existed between the rate of cell division and the percentage of cultures forming embryos; the latter decreased with increasing numbers of cell generations. It is probable that the observed morphogenetic variations depend at least partially upon epigenetic changes which occur during growth and differentiationin vitro.