Showing papers by "University of Freiburg published in 1977"

Human papillomaviruses and their possible role in squamous cell carcinomas.

Abstract: The view that common warts (verrucae vulgares), juvenile warts (verrucae planae), and genital warts (condylomata acuminata) are caused by the same virus and that differences in appearance are the result of variations in location and host reactivity has been shared by dermatologists for several decades (Frey, 1924; Waelsch and Habermann, 1924; Young, 1964; Rowson and Mahy, 1967; Nasemann, 1974; Lever and Schaumburg-Lever, 1975). This has probably reduced the interest in specific types of human papillomas.

Solid-state polymerization mechanisms

Abstract: Mechanisms of topochemical polymerizations are described using the four-center-type photopolymerization of diolefins and the polymerization of diacetylenes as actual examples. Solid-state polymerizations can be treated as a special case of phase change which may proceed homogeneously or heterogeneously. Special consequenses of the mechanism of phase change are described. The scope of the four-center-type and of diacetylene polymerization is discussed and some rules relating molecular shape and packing into a reactive modification are discussed. Photoresponse curves for diacetylenes are reported and the relation between molecular structure and photosensitivity is discussed. Finally, the nature of chain growth is considered. Four-center-type photopolymerization proceeds in an stepwise manner along the same mechanism which is also true for dimerization of cinnamic acids and derivatives. Diacetylene polymerization proceeds via carbenoid intermediates which add to polymer chain ends with carbene character.

Presynaptic receptor systems on the noradrenergic neurones of rat brain.

Abstract: Occurrence and properties of receptors modulating release of noradrenaline were studied in slices of rat occipital cortex and, less extensively, of rat hypothalamus and cerebellar cortex The slices were preincubated with 3H-noradrenaline and then superfused and stimulated either electrically at 1–3 Hz or by 15–20 mM potassium (1) Omission of calcium abolished the electrically and potassium-evoked overflow of tritium Tetrodotoxin blocked the electrically evoked overflow and reduced the response to potassium The electrically evoked overflow of total tritium consisted of 80% 3H-noradrenaline and 19% 3H-3,4-dihydroxyphenylglycol (DOPEG) Cocaine strongly decreased the electrically evoked overflow of 3H-DOPEG The overflow of tritium evoked by 15 mM potassium also contained mainly 3H-noradrenaline with only a minor part of 3H-DOPEG (2) Both the electrically and the potassium-evoked overflow of tritium were reduced by unlabelled noradrenaline (in the presence of cocaine) and tramazoline, and increased by phentolamine and yohimbine The changes in the evoked overflow of total tritium reflected approximately proportionate changes of 3H-noradrenaline and 3H-DOPEG (3) Both the electrically and the potassium-evoked overflow of tritium were reduced by morphine and methionine-enkephalin 3H-noradrenaline and 3H-DOPEG were proportionately decreased Dextrorphan, in contrast to its analgesically active enantiomer levorphanol, had no effect Inhibition by morphine persisted after pretreatment with indometacin (4) Prostaglandin E1 reduced both the electrically and the potassium-evoked overflow of tritium 3H-noradrenaline and 3H-DOPEG were proportionately decreased (5) Phentolamine antagonized the inhibitory effect of noradrenaline, but not that of morphine, enkephalin, and prostaglandin E1 Naloxone antagonized the effect of enkephalin, but not that of tramazoline and prostaglandin E1 (6) Acetylcholine (up to 10−5 M) and oxotremorine (up to 10−4 M) failed to reduce the electrically and potassium-evoked overflow Moreover, atropine (up to 3×10−6 M) had no effect Up to 10−3 M acetylcholine (in the presence of atropine) as well as up to 10−4 M nicotine did not change the basal outflow of tritium in the absence of releasing stimuli 10−3 M nicotine caused an increase which was not changed by hexamethonium or omission of calcium In contrast to the overflow evoked by electrical stimulation or high potassium, the overflow evoked by nicotine mainly consisted of 3H-DOPEG with only a minor part attributable to 3H-noradrenaline (7) γ-Aminobutyric acid slightly enhanced both the basal and (maximally by 27%) the electrically evoked overflow Histamine (in the presence of cocaine) slightly decreased the electrically evoked overflow (maximally by 17%) (8) The following drugs did not change the electrically evoked overflow of tritium: dopamine (in the presence of cocaine), isoprenaline (up to 10−6 M), propranolol (up to 10−6 M), serotonin (in the presence of cocaine), angiotensin I, angiotensin II, saralasin, and substance P (9) It is concluded that transmitter release from the noradrenergic neurones of several brain areas is modulated by drugs acting on α-adrenoceptors, opiate receptors, and prostaglandin receptors It seems likely, though by no means certain, that the receptors involved are located on the noradrenergic nerve endings themselves, ie, that they are presynaptic receptors No evidence was obtained for presynaptic dopamine, β-, muscarine, nicotine, and angiotensin receptors This pattern differs from that found in other tissues, thus substantiating marked tissue differences in presynaptic receptor systems

Transposable genetic elements as agents of gene instability and chromosomal rearrangements

Abstract: Transposable genetic elements in prokaryotes and eukaryotes, when inserted at a given locus, can control expression of the locus and cause large scale rearrangements of adjacent DNA sequences. Striking similarities in genetic behaviour between the two groups of elements have led to the proposal of a molecular model of eukaryotic controlling elements, and to suggestions about the part such elements may play in evolution and differentiation.

The triple helix ⇌ coil conversion of collagen‐like polytripeptides in aqueous and nonaqueous solvents. Comparison of the thermodynamic parameters and the binding of water to (L‐Pro‐L‐Pro‐Gly)n and (L‐Pro‐L‐Hyp‐Gly)n

Abstract: The collagen-like peptides (L-Pro-L-Pro-Gly)n and (L-Pro-L-Hyp-Gly)n with n = 5 and 10, were examined in terms of their triple helix ⇌ coil transitions in aqueous and nonaqueous solvents. The peptides were soluble in 1,2-propanediol containing 3% acetic acid and they were found to form triple-helical structures in this solvent system. The water content of the solvent system and the amount of water bound to the peptides were assayed by equilibrating the solvent with molecular sieves and carrying out Karl Fischer titrations on the solvent phase. After the solvent was dehydrated, much less than one molecule of water per tripeptide unit was bound to the peptides. Since the peptides remained in a triple-helical conformation, the results indicated that water was not an essential component of the triple-helical structure. Comparison of peptides with the same chain length demonstrated that the presence of hydroxyproline increased the thermal stability of the triple helix even under anhydrous conditions. The results, therefore, did not support recent hypotheses that hydroxyproline stabilizes the triple helix of collagen and collagen-like peptides by a specific interaction with water molecules. Analysis of the thermal transition curves in several solvent systems showed that although the peptides containing hydroxyproline had tm values which were 18.6° to 32.7°C higher, the effect of hydroxyproline on ΔG was only 0.1 to 0.3 kcal per tripeptide unit at 25°C. The results suggested, therefore, that the influence of hydroxyproline on helical stability may be explained by intrinsic effects such as dipole–dipole interactions or by changes in the solvation of the peptides by alcohol, acetic acid, and water. A direct calorimetric measurement of the transition enthalpy for (L-Pro-L-Pro-Gly)n in 3% or 10% acetic acid gave a value of −1.84 kcal per tripeptide unit for the coil-to-helix transition. From the value for enthalpy and from data on the effects of different chain lengths on the thermal transition, it was calculated that the apparent free energy for nucleation was +5 kcal/mol at 25°C (apparent nucleation parameter = 2 × 10−4M−2). The value was dependent on solvent and on chemical modification of end groups.

Inhibition of the slow inward current by nifedipine in mammalian ventricular myocardium.

Abstract: In order to elucidate the mode of action of the Ca2+-antagonistic inhibitor nifedipine, its effect on Ca2+-mediated action potentials and transmembrane slow inward current in papillary muscles of guinea pigs and cats was studied. Nifedipine (0.5 mg/1 approximately 1.4 X 10(-6) M) depressed upstroke velocity and overshoot of the Ca2+-mediated action potential and reduced the transmembrane slow inward current by about 50%, but the kinetics of inactivation and recovery from inactivation were not affected. The decrease of upstroke velocity was accompanied by a proportional diminution of isometric contractile force. This indicates that nifedipine exerts its Ca2+-antagonistic effect on excitation-contraction coupling in mammalian ventricular myocardium by inhibition of the transmembrane Ca2+ inward current. The inhibitory action of nifedipine on contractile tension development could be neutralized by an augmentation of the extracellular Ca2+ concentration from 2 mM to 4 mM or by beta-receptor stimulation (isoproterenol) that promotes the transmembrane Ca2+ uptake during excitation. Simultaneously, in the Ca2+-rich medium or under the influence of isoproterenol the upstroke velocity of the Ca2+-mediated action potentials rose even above the initial values which were measured prior to the nifedipine administration.

Characterization of naphthaleneacetic Acid binding to receptor sites on cellular membranes of maize coleoptile tissue.

Abstract: Characteristics of and optimum conditions for saturable (“specific”) binding of [14C]naphthaleneacetic acid to sites located on membranous particles from maize (Zea mays L.) coleoptiles are described. Most, if not all, of the specific binding appears to be due to a single kinetic class of binding sites having a KD of 5 to 7 × 10−7m for naphthalene-1-acetic acid (NAA). Binding of NAA is insensitive to high monovalent salt concentrations, indicating that binding is not primarily ionic. However, specific binding is inhibited by Mg2+ or Ca2+ above 5 mm. Specific binding is improved by organic acids, especially citrate. Binding is heat-labile and is sensitive to agents that act either on proteins or on lipids. Specific binding is reversibly inactivated by reducing agents such as dithioerythritol; a reducible group, possibly a disulfide group, may be located at the binding site and required for its function. The affinity of the specific binding sites for auxins is modified by an unidentified dialyzable, heat-stable, apparently amphoteric, organic factor (“supernatant factor”) found in maize tissue.

Specificity of Auxin-binding Sites on Maize Coleoptile Membranes as Possible Receptor Sites for Auxin Action

Abstract: Dissociation coefficients of auxin-binding sites on maize (Zea mays L.) coleoptile membranes were measured, for 48 auxins and related ring compounds, by competitive displacement of 14C-naphthaleneacetic acid from the binding sites. The sites bind with high affinity several ring compounds with acidic side chains 2 to 4 carbons long, and much more weakly bind neutral ring compounds and phenols related to these active acids, most phenoxyalkylcarboxylic acids, and arylcarboxylic acids except benzoic acid, which scarcely binds, and triiodobenzoic acids, which bind strongly. Specificity of the binding is narrowed in the presence of a low molecular weight “supernatant factor” that occurs in maize and other tissues. Activity of many of the analogs as auxin agonists or antagonists in the cell elongation response was determined with maize coleoptiles. These activities on the whole roughly parallel the affinities of the binding sites for the same compounds, especially affinities measured in the presence of supernatant factor, but there are some quantitative discrepancies, especially among phenoxyalkylcarboxylic acids. In view of several factors that can cause receptor affinity and biological activity values to diverge quantitatively among analogs, the findings appear to support the presumption that the auxin-binding sites may be receptors for auxin action.

Vision in insects: pathways possibly underlying neural adaptation and lateral inhibition

Abstract: Like horizontal cells in vertebrate retinas, horizontal amacrine cells beneath the insect eye intervene between receptors and interneurons at the first level of synapses. Synaptic arrangements between amacrines and interneurons that give rise to regular networks of axon collaterals may explain recent electrophysiological observations of lateral inhibition beneath the insect retina. Neural adaptation mechanisms acting on single retinotopic channels or assemblies of channels can also be referred to reciprocal relationships between receptors and first-order interneurons as well as to centrifugal cells from levels of so-called photopic receptor endings.

Strong Correlation Effects in inner Valence Ionization of N2 AND CO

Abstract: The results of many-body calculations of the valence and inner-valence ionization potentials and their intensities are reported for N2 and CO. For N2 we find that the 2σg line is smashed to several pieces of roughly equal intensity. It is not possible to identify any of these lines as the ǒmainǒ line representing the ionization of a 2Ug electron and the remaining ones as satellite lines. For CO there survives a line which carries about half of the 3e intensity and which can be interpreted to represent the ionization of an electron out of the 3σ orbital. The results explain the peculiar shape of the broad innervalence peaks of N2 and CO. For both N2 and CO rich satellite structure is found in qualitative agreement with experimental X-ray photoelectron spectra.

Vibronic coupling and symmetry breaking in core electron ionization

Abstract: It is shown that for highly symmetric molecules the ionization of a core electron leads quite generally to a lowering of the symmetry. The breaking of the symmetry is a consequence of the vibronic coupling between nearly degenerate core orbitals of different symmetry. The vibronic coupling leads to strong excitation of non-totally symmetric vibrational modes in addition to the usually observed excitation of totally symmetric modes. As an example, the vibrational structure of the Ols line of the CO 2 molecule is computed on the one-particle level.

Colour vision in Drosophila melanogaster

Abstract: Using a fully automatized procedure and a training scheme symmetrical with respect to the visual stimuli as well as to the aversive stimulus,Drosophila could be conditioned to blue and yellow lights. With constant test conditions and variation of the light intensities during the training procedure, it could be shown that the flies respond primarily to the colour of the light.

Polymerization of mono- and multilayer forming diacetylenes

Abstract: Heptadeca-2,4-diine-1-ol and Heptadeca-2,4-diine-1-acid were synthesized and their polymerization behaviour in the solid state was investigated. Both compounds polymerize thermally below the melting point and photochemically under the action of uv-light to form polymers via 1,4-addition to the conjugated triple bonds with a backbone of conjugated double-and triple-bonds. The photoresponse spectra resemble the absorption spectra exhibiting maxima of photoreactivity in the absorption band of the conjugated triple bonds of the monomers.

Long-term side effects in irradiated patients with Hodgkin's disease

Abstract: 135 out of 168 patients with Hodgkin's disease in complete remission who had received radiotherapy with tumor doses between 3000 and 5000 rad in the years 1948–1974 were investigated with regard to long-term side effects. The results obtained so far are as follows: 1.1. Catamnestic results: Deteriorated general condition and reduced performance in 23% and 28%, spontaneous restriction of the daily routine in 45% and increase in susceptibility to infections (common cold) in 15% of the patients 2.2. Hematological investigations, (a) Peripheral blood: No indication of severe anemia. Granulocytopenia with less than 3000 cells/mm 3 in 18.5%, lymphocytopenia with less than 2000 cells/mm 3 in 37%, no incidence of thrombocytopenia with less than 100,000 platelets/mm 3 or leukemia. (b) Sternal marrow cytology (locally irradiated): Aplasia in 76%, hypoplasia in 18%. No signs of leukemia. (c) Iliac crest cytology (not directly irradiated): Slight hypoplasia in 38%, severe hypoplasia in 8%, no signs of leukemia. 3.3. Pulmonary investigations: Slight paramediastinal fibrosis in 44%, distinct in 36% and severe in 9%. Restrictive ventilation disorder in 84%, increase in residual volume in 61%, O 2 -diffusion disorder in 18% and obstructive ventilation disorder in 7% of the patients. 4.4. Cardiological investigations: Under stress pulmonary hypertension in 18%, right ventricular function disorder in 9%, left ventricular function disorder in 9%, cardiac insufficiency in 2%, restriction of the maximum ergometer cycling exercise capacity in 53% of the patients. 5.5. Thyroid function investigations: Hypothyroidal or latent hypothyroidal thyroid insufficiency in 16.5%. 6.6. Neurological symptomatology (excluding herpes zoster): Slight to moderately severe double-sided cross section symptomatology in 3 of 122 patients (2.5%), bilateral or unilateral plexus paresis in 4 of 122 patients (3.5%). 7.7. Genito-urinary tract (male) investigations: Infertility (azoospermia, asemia, akinesis) following infradiaphragmatic irradiation using the inverted Y-method in 70%, restricted fertility (oligo-, astheno-, teratospermia) in 26% of the cases (in spite of the constant usage of a testicular capsule). 8.8. Dermatological investigations: According to the number of patients, teleangiectasis, induration of the irradiated fields, and medium to severe irradiation discomfort occured in 22, 15.6 and 8% respectively.

Grundlagen und Grenzen des Reaktivitäts‐Selektivitätsprinzips

Abstract: Das Reaktivitats-Selektivitatsprinzip (RSP), das einen linearen Zusammenhang zwischen der Abnahme der Selektivitat mit Zunahme der Reaktivitat von Molekulen Xm in ihren Umsetzungen mit Y1 und Y2 beschreibt, ist in den letzten Jahren mehrfach kritisiert worden. Es wird gezeigt, bei welchen Reaktionen das RSP versagt und wie durch Losungsmittelvariation die einzelnen Reaktionstypen voneinander unterschieden werden konnen. Einen zusatzlichen Effekt ruft die Temperaturabhangigkeit der Molekulselektivitaten hervor. Ihre Berucksichtigung fuhrt zur isoselektiven Beziehung (ISR). In ihr werden nicht mehr die temperaturabhangigen Geschwindigkeits- und Konkurrenzkonstanten, sondern die uber grose Bereiche temperaturunabhangigen Aktivierungsenthalpien und Aktivierungsentropien miteinander in Beziehung gesetzt. Die Anwendung der ISR auf verschiedenartige Reaktionen ermoglicht die Charakterisierung und Unterscheidung kurzlebiger Zwischenstufen und weist auf die Bedeutung der isoselektiven Temperatur (Tis) fur die Interpretation von Reaktionsparametern linearer „Freie Energie”-Beziehungen und fur die Syntheseplanung hin.

Physiology of Mating in Three Yeasts

Abstract: Publisher Summary This chapter compares the steps in the mating process in three species of yeasts. The various physiological factors, events, and regulatory phenomena that are part of the mating process are described for Hansenula wingei, Schizosaccharomyces pombe, and Saccharomyces cerevisiae . All three yeasts are found in Nature growing saprophytically on plant sugars and related compounds, but their symbiotic associations are significantly different. While their industrial importance results from their fermentative abilities, their mating processes occur optimally under aerobic conditions. Yeast-cell mating involves both temporal and spatial organization of biochemical reactions which lead to new form and function. The organization and sequence of reactions are controlled genetically, not only by the genes governing individual reactions but also by a central locus, the mating-type locus (mat) that governs expression of conjugation-specific genes. The similarities and differences among these yeast systems are discussed. Emphasis in this chapter is laid on recent observations as reviews of earlier work are available for each mating system. The three yeasts reviewed are diverse in terms of their ecological niches, metabolism, morphology, and life cycles. Therefore, for a better understanding of the physiology of sexual reproduction in these organisms, it is necessary to consider these characteristics.

Theory of the vibrational structure of resonances in electron-molecule scattering

Abstract: We derive a simple Hamiltonian representing the coupling of an electronic level of positive energy to the continuum of scattering states as well as to the molecular vibrations. By summing the perturbation series for the $S$ matrix to infinite order in the bound-state-continuum interaction, an effective non-Hermitian boson Hamiltonian describing the dynamics of vibrational motion in the resonance state is obtained. It is shown that the effective Hamiltonian can be diagonalized, yielding explicit expressions for the vibrational excitation cross sections. The theory is applied to two representative examples, the 3.8-eV shape resonance in C${\mathrm{O}}_{2}$ and the 2.4-eV shape resonance in ${\mathrm{N}}_{2}$. The results exhibit a clear improvement over those obtained with existing theories, which express the cross sections in terms of conventional Franck-Condon factors. The influence of the anharmonicity of the potential functions on the structure of the vibrational excitation functions is discussed.

Biochemistry of lignification

Abstract: The complete set of enzymes that catalyze the reactions from l-phenylalanine to substituted cinnamyl alcohols is now known. The latter compounds are the primary building stones of lignin. The individual reactions and the possible modes of regulation of this pathway are discussed. The polymerization of cinnamyl alcohols to lignin is mediated by peroxidase. The significance of cell-wall-bound peroxidases in this process and the origin of hydrogen peroxide are reviewed. Finally, the possible role of lignification in relation to disease resistance is discussed.

Studies on a Carboxypeptidase Y Mutant of Yeast and Evidence for a Second Carboxypeptidase Activity

Abstract: Immunological studies on the carboxypeptidase Y mutant prcl-l of Saccharomyces cerevisiae revealed the origin of mutation in the structural gene of carboxypeptidase Y. The absence of carboxypeptidase Y has no effect on growth, even after drastic changes of growth conditions. A double mutant (prc 1- leu2-) lacking carboxypeptidase Y and auxotrophic for leucine is able to grow on the peptide benzyloxycarbonylglycylleucine (Cbz-Gly-Leu) as sole nitrogen source, indicating the existence of a second carboxypeptidase. Using a new peptidase test, the existence of this second enzyme, called carboxypeptidase S, was confirmed biochemically.

Enzymes of flavone and flavonol-glycoside biosynthesis. Coordinated and selective induction in cell-suspension cultures of Petroselinum hortense.

Abstract: We have extended our previous studies, which had resulted in the classification of two groups of coordinately induced enzymes of phenylpropanoid metabolism in irradiated cell-suspension cultures of Petroselinum hortense Hoffm. The additional enzymes investigated were acetyl-CoA carboxylase, a methyltransferase, and a flavonol-specific glucosyltransferase. The results indicate that the second group (group II) includes the enzymes of both flavone and flavonol glycoside formation from 4-coumaroyl-CoA and acetyl-CoA (utilized via malonyl-CoA). The enzymes of this pathway, as opposed to those of the general phenylpropanoid metabolism (group I), met the following operational criteria for their common classification into group II. Under the experimental conditions employed, they increased in activity after a considerably longer, but uniform, lag period of about 4 h, as compared with about 2 h for group I; pronounced peaks of the individual enzyme activities in the range between about 25 and 40 h after the onset of induction occurred significantly later than in the case of group I; subsequent periods of exponential decline of the enzyme activities occurred with relatively long apparent half-lives of the order of 30–70 h. The induction of the two groups of enzymes was shown to be highly selective. Several enzymes involved in various pathways of intermediary metabolism were not affected by irradiation of the cell cultures. Even those enzymes, which are assumed to catalyze the formation of the various intermediary metabolites serving as substrates for the light-induced reactions, remained unaffected by the irradiation program.