Showing papers by "University of Basel published in 1977"

Deuterium magnetic resonance: theory and application to lipid membranes.

Abstract: Proton and carbon-13 nmr spectra of unsonicated lipid bilayers and biological membranes are generally dominated by strong proton–proton and proton–carbon dipolar interactions. As a result the spectra contain a large number of overlapping resonances and are rather difficult to analyse. Nevertheless, important information on the structure and dynamic behaviour of lipid systems has been provided by these techniques (Wennerstrom & Lindblom, 1977).

History of the Mediterranean salinity crisis

Abstract: A history of geodynamic evolution of the Mediterranean leading to the salinity crisis is outlined, based on the ‘desiccated deep-basin model’. An accurate portrayal of the crisis is presented, based on data from new drilling and studies of on-land geology.

Valence Ionization Energies of Hydrocarbons

Abstract: Experimental valence ionisation energies of 143 hydrocarbons, CnHm, have been determined from their He (IIα) (40.80 eV) and He (Iα) (21.22 eV) excited photoelectron spectra. Ionization energies, usually up to 26 eV are given in tabular form for 108 hydrocarbons with n≤6, together with their (tentative) assignment. The ionization energies up to approximately 25 eV, of 35 selected hydrocarbons with 7≤n≤10, are presented by means of their He (IIα) photoelectron spectra.

Fundoplication for the treatment of gastroesophageal reflux in hiatal hernia

Abstract: Fundoplication, using an abdominal approach, is advocated to create an adequate substitute for the insufficient sphincter in gastroesophageal reflux associated with hiatus hernia. To achieve success, correct indications for surgical treatment are important. Based on experience with approximately 1,400 patients over the past 20 years, these include: (a) a retrosternal burning sensation (in 90% of our cases); (b) objective confirmation of reflux by means of x-ray and endoscopic examination, together with biopsy examination of the esophageal mucosa and gastric acid evaluation; and (c) evidence of organic complications such as endobrachyesophagus with ulcerostenotic changes at the junction between the esophageal and gastric mucosa. Long-term follow-up of 590 patients with simple reflux esophagitis who underwent fundoplication showed that 87.5% were symptom free. In 44 patients with complicated gastroesophageal reflux disease, fundoplication produced clinical healing in 84.1%.

Electromagnetic structure of the helium isotopes

Abstract: The elastic-electron scattering cross sections from $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ have been measured at incident electron energies between 170 and 750 MeV. Cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. Values of the $^{3}\mathrm{He}$ charge form factor have been extracted to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and for the $^{3}\mathrm{He}$ magnetic form factor to ${q}^{2}=16$ ${\mathrm{fm}}^{\ensuremath{-}2}$. The $^{4}\mathrm{He}$ form factor has been determined up to 6.2 ${\mathrm{fm}}^{\ensuremath{-}2}$. Densities for the charge and magnetization have been deduced from phenomenological models used in a phase-shift solution of the Dirac equation. A model-independent determination of the nuclear densities has been performed in order to obtain realistic errors on the extracted distributions. After unfolding the nucleon size from the distributions the point density is shown to have a significant central depression for a radius 0.8 fm for both $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$. Comparison of the form factors is made with Faddeev and variational three-body calculations that use realistic two-body $\mathrm{NN}$ interactions. The influence of off-shell effects, three-body forces, meson-exchange corrections, and short-range correlations are discussed. At present no theoretical calculation that uses input derived entirely from nucleon-nucleon scattering is able to reproduce the experimental data.NUCLEAR REACTIONS $^{3,4}\mathrm{He}(e, {e}^{\ensuremath{'}})$, $E=170, 200, 250, 300, 350, 400, 450, 500, \mathrm{and} 750$ MeV; measured $\ensuremath{\sigma}(E, \ensuremath{\theta})$. Measured charge form factor $^{3}\mathrm{He}$ to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and magnetic form factor to ${q}^{2}=16$ ${\mathrm{fm}}^{\ensuremath{-}2}$. Measured $^{4}\mathrm{He}$ form factor to ${q}^{2}=6.2$ ${\mathrm{fm}}^{\ensuremath{-}2}$. Deduced nuclear charge, magnetic and point-nucleon distributions from model-independent analysis.

A simple, general procedure for purifying restriction endonucleases

Abstract: A simple, general method for purifying restriction endonucleases is described. The method employs precipitation of nucleic acids from crude extracts with polyethyleneimine followed by affinity chromatography on columns of heparin covalently linked to agarose. Most of the sixteen enzymes tested could be purified to a degree sufficient for DNA sequencing work by this method sometimes supplemented by at most one step of ion exchange chromatography.

Non-metastasising variants selected from metastasising melanoma cells

Abstract: THE cell surface may be involved in the metastatic process of cancer cells1. To determine whether membrane properties influence or reflect the metastasising capacity, it is essential to have metastasising and non-metastasising variants of the same tumour. Lectins which bind specifically to surface carbohydrates2 have been used successfully as selective agents to obtain cells with membrane carbohydrate alterations3–5. We have selected variants of melanoma cells for surface differences in using toxic concentrations of lectins in the hope that such variants would exhibit different metastasising capacities. We report here the isolation of variants from metastasising melanoma cells resistant to toxic concentrations of wheat germ agglutinin (WGA). These variants show reduced to a loss of metastasising capacity and altered surface properties.

The Photoenolization of 2-Methylacetophenone and Related Compounds

Abstract: A reinvestigation of 2-methylacetophenone (1) by ns flash photolysis has provided detailed evidence for the reaction sequence of photoenolization. The triplet reaction proceeds adiabatically from the lowest excited triplet state of the ketone, 3K (1), to the enol excited triplet state, 3E (1), which decays both to enol and ketone ground state. The Z- and E-isomers of the photoenol, Z-E (1) and E-E (1) are formed in about equal yield by the triplet pathway, while direct enolization from the lowest excited singlet state of 1 yields (predominantly) the Z-isomer. Intramolecular reketonization from Z-E (1) to 1 proceeds at a rate of ca. 108s−1 in cyclohexane, but can be retarded to ca. 104s−1 in hydrogen-bond-acceptor solvents. The proposed mechanism is summarized in Scheme 1 and rationalized on the basis of a state correlation diagram, Scheme 2. 3,3,6,8-Tetramethyl-1-tetralone (2) was used as a reference compound with fixed conformational position of the carbonyl group, and some results from a brief investigation of 2,4-dimethylbenzophenone (3) are also reported.

Physical Mapping of BglII, BamHI, EcoRI, HindIII and PstI Restriction Fragments of Bacteriophage P1 DNA

Abstract: A cleavage map of bacteriophage P1 DNA was established by reciprocal double digestion with various restriction endonucleases. The enzymes used and, in parenthesis, the number of their cleavage sites on the P1clts genome are: PstI (1), HindIII (3), BglII (11), BamHI (14) and EcoRI (26). The relative order of the PstI, HindIII and BglII sites, as well as the order of 13 out of the 14 BamHI sites and of 17 out of the 26 EcoRI sites was determined. The P1 genome was divided into 100 map units and the PstI site was arbitrarily chosen as reference point at map unit 20.

Ion-induced changes in head group conformation of lecithin bilayers

Abstract: THE structure and orientation of the phosphocholine polar group in lecithin-containing membranes has been discussed extensively. Studies of egg-yolk lecithin and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), using neutron diffraction and 2H and 31P nuclear magnetic resonance (NMR), have led to the conclusion that the phosphocholine dipole is orientated parallel to the membrane surface1–4. On the other hand, 1H and 31P NMR spectra of sonicated DPPC vesicles in the presence of trivalent ions suggested that the choline group is extended approximately perpendicular5 or folded parallel6 to the bilayer surface. We have, therefore, repeated our previous 2H and 31P NMR measurements in the presence of trivalent ions and report here that the addition of these shift reagents induces large changes in the spectral parameters, that is, the 2H quadrupole splittings and the 31P chemical shift anisotropy. These observations can only be interpreted in terms of specific ion-induced changes in the choline head group conformation of DPPC.

Interaction of RNA polymerase with promoters from bacteriophage fd.

Abstract: Replicative form DNA of bacteriophage fd, which had been fragmented with the restriction endonuclease II from Hemophilus parainfluenzae (endo R ·HpaII), was reacted with Escherichia coli RNA polymerase; the resulting stable preinitiation complexes were analysed using the filter binding assay followed by gel electrophoresis. At 120 mM KCl the first-order rate constants for complex decay were determined to be 10−2–10−6s−1. The second-order rate constants for complex formation were found to be about 106–107 M−1 s−1. From these values association constants for the individual promoters were calculated to be 2 × 10−8–2 × 10−11 M−1. The rate of formation and the stability of promoter complexes was enhanced in superhelical DNA. No evidence was found for stable promoter-specific closed complexes consisting of enzyme and helical DNA. This and the kinetic data suggest that the unwinding of base pairs is already important early in promoter selection, and not only for the formation of the final open complex. The initiation of RNA synthesis from the preinitiation complex was faster than complex dissociation and complex formation for all promoters. Consequently, the initiation efficiency of a promoter is determined by the rate of complex formation, and not by its ‘affinity’ for the enzyme. No correlation was found between the relative order of the fd promoters for the binding and the dissociation reaction. This is explained by different structural determinants, for the two reactions, which are located in different parts of the promoter DNA.

High-Momentum-Transfer Electron Scattering from Pb 208

Abstract: $^{208}\mathrm{Pb}$ elastic electron scattering data have been extended to large momentum transfer ($q=3.7$ ${\mathrm{fm}}^{\ensuremath{-}1}$). The present data combined with previous electromagnetic data allow a precise determination of the charge density. It shows a small central depression and density fluctuations much less pronounced than theoretically predicted.

Time evolution, correlations, and linear response of non-Markov processes

Abstract: We investigate the time evolution of stochastic non-Markov processes as they occur in the coarse-grained description of open and closed systems. We show that semigroups of propagators exist for all multivariate probability distributions, the generators of which yield a set of time-convolutionless master equations. We discuss the calculation of averages and time-correlation functions. Further, linear response theory is developed for such a system. We find that the response function cannot be expressed as an ordinary time-correlation function. Some aspects of the theory are illustrated for the two-state process and the Gauss process.

Adenylate cyclase activity oscillations as signals for cell aggregation in Dictyostelium discoideum.

Abstract: As well as acting as a chemotactic factor1 cyclic AMP stimulates cells of Dictyostelium discoideum to differentiate after the end of growth into aggregation-competent cells. These differentiation signals have a temporal pattern : pulses are efficient signals, whereas continuous administration of cyclic AMP may even have an adverse effect2,3. D. discoideum cells can release cyclic AMP spontaneously as reiterated pulses4, and also release cyclic AMP in response to extraneous cyclic AMP pulses5–7, which is important for the transmission of signals in aggregation territories in form of propagated waves8–12. The pulsatile release of cyclic AMP into the extracellular space is preceded by a sharp (about 10-fold) increase of its intracellular concentration within 1 min (ref. 4). This indicates that the oscillating variable is not only transport but also net synthesis of cyclic AMP. The periodic rise of the intracellular cyclic AMP concentration could be due to periodic activation of adenylate cyclase, to inhibition of phosphodiesterase, or to the oscillatory control of both enzymes. We present here evidence for sustained oscillations of the adenylate cyclase activity in signalling cells. No concomitant changes of the ATP concentration, the substrate of adenylate cyclase, were found.

Genetic analysis of pattern-formation in the embryo ofDrosophila melanogaster : Characterization of the maternal-effect mutantBicaudal.

Abstract: The mutationbicaudal (Bull, 1966) causes embryos to develop a longitudinal mirror image duplication of the posteriormost abdominal segments, while head and thorax are missing. These embryos occur with varying frequencies among eggs laid by mutant females, irrespective of the paternal genotype. Recombination and deletion mapping indicate thatbicaudal (bic) is a recessive, hypomorphic, maternal-effect mutation mapping at a single locus on the second chromosome ofDrosophila melanogaster close tovg (67.0±0.1). The frequency of bicaudal embryos depends on the age of the mother, her genetic constitution and the temperature at which she is raised. Best producers are very young females hemizygous forbic (bic/Df(2)vg B ) at 28° C. Under these conditions 80% to 90% of the eggs which differentiate can show the bicaudal embryo phenotype. Upon ageing of the mother the frequency of bicaudal embryos declines rapidly, and most of the eggs develop the normal body pattern. Temperature shift experiments suggest a temperature-sensitive period at the onset of vitellogenesis.The mutation causes several types of abnormalities in the segment pattern of theDrosophila embryo, which are interpreted as various degrees of expression of the mutant character. The most frequent abnormal phenotype is the symmetrical bicaudal embryo with one to five abdominal segments duplicated. Less frequent are asymmetrical types, in which the smaller number of segments is always in the anterior reversed part. Other phenotypes are embryos with missing or rudimentary heads, and embryos with irregular gaps in the segment pattern. In bicaudal embryos, the pole cells, formed at the posterior pole of the egg prior to blastoderm formation, are not duplicated at the anterior. The significance of thebicaudal phenotypes for embryonic pattern-formation inDrosophila is discussed.

Sex determination in germ line chimeras of Drosophila melanogaster.

Abstract: Of 55 flies developing from blastoderms which had received male or female pole cell transplants, 15 (7 females and 8 males) wer shown by progeny testing to be germ line chimeras. Since donor and host pole cells were genetically marked with contrasting X- or Y-linked alleles, the progeny testing scheme enabled the genotypic sex of the donor component undergoing gametogenesis to be identified as either the same as ('homosexual' chimeras) or opposite ('heterosexual' chimeras) that of the host. All seven of the female chimeras were identified as 'homosexual' chimeras carrying only chromosomally female XYX donor and XX host germ cells. Similarly, all eight males were shown to be 'homosexual' chimeras with chromosomally male XY donor and XY host germ cells. The chromosomal sex of the donor component undergoing gametogenesis was in every case the same as the phenotypic sex of the host. Since there is an equal probability of constructing either a 'homosexual' or a 'heterosexual' chimera during pole cell transplantation, the ability of pole cells to differentiate functional gametes in hosts of the opposite sex was tested 50% of the time even if sex reversal of these donor pole cells could not be demonstrated. Thus the absence of 'heterosexual' chimerism strongly supports the interpretation that the phenotypic sex of a germ cell in Drosophila is determined entirely by its own chromosome constitution, not by that of the gonadal mesoderm.

alpha-Actinin attached to membranes of secretory vesicles.

Abstract: THE role of microfilaments in secretion has been much debated1–4 If secretion involves a sliding filament mechanism similar to muscle contraction5, microfilaments must attach at least transiently to vesicle membranes Indeed, there is evidence that contractile proteins are associated with secretory vesicles (chromaffin granules) of adrenal medulla6,7 Moreover, the outer (cytoplasmic) surface of secretory vesicles must provide ‘anchoring molecules’ for microfilaments In skeletal muscle, the structural protein α-actinin located in the Z-line8 serves as such an anchoring molecule An α-actinin-like protein was isolated from a variety of non-muscle cells9,10 and there is evidence that the same protein is attached to the inner (cytoplasmic) surface of the plasma membrane of non-muscle cells in association with microfilaments11–14 Using a monospecific antibody to porcine α-actinin (Fig 1) we have demonstrated the presence of this protein in secretory vesicle membranes from chromaffin cells of the adrenal medulla and from platelets

Radative relaxation of the B̃(π -1 )EXCITED Electronic States of the Radical Cations of Rexafluorobenzene, Pentafluorobenzene, 1,2,3,4-, 1,2,3,5-, 1,2,4,5-TETRAFLUOROBENZENE, 1,3,5-, 1,2,4-TRIFLUOROBENZENE and 1,3-DIFLUOROBENZENE

Abstract: The lifetimes of the zeroth and some vibiationally excited levels of the B(π-1) states of the radical cations of hexafluorobenzene (1), pentafluorobenzene (2), 1,2,3,4- (3), 1,2,3,5- (4) and 1,2,4,5-(5)-tetrafluorobenzene, 1,3,5- (6) and 1,2,4- (7)-trifluorobenzene in the aaseous phase have been measured. The cations were produced by 20—30 eV electron beam excitation of the samples at pressures < 10-3 torr The 00 level lifetimes (± 2 ns) found were 1 -48 us, 2 -47 ns, 3 - 50 ns, 4 - 50 ns, 5 - 30 ns, 6 - 58 os and 7 - 10 ns. The emission of 1,3-difluoralienzene radical cation (8) has also now been detected and the emission spectra of the fluorobenzenes 1-8,B → A, X band systems, are discussed. The emission intensities of the B →A, X transitions have been determined for 2-8 relative to 1. The lack of detectable emission from the corresponding excited (ir1) states of the radIcal cations of 1,4-and 1,2-difluorobeozene, fluorobeuzene, besizene and benzene-d6 indicates that the quantum yields of emission are < 10-5. The implications of the positive and negative results are considered with respect to the electronic structures of these species and the possible non-radiative pathways accessible to such excited cations.

Structure and assembly of bacteriophage lambda.

Abstract: Bacteriophage λ has an icosahedral head with a radius of 30 nm and a flexible tail 150 nm long (Fig. lb; Kellenberger, 1961; Eiserling and Boy de la Tour, 1965; Kemp et al., 1968; Eiserling as quoted in Kellenberger and Edgar, 1971; Bayer and Bocharov, 1973; Mazza and Felluga, 1973; Harrison et al., 1973).

Plaque forming specialized transducing phage P1: Isolation of P1CmSmSu, a precursor of P1Cm

Abstract: E. coli strains lysogenic for various types of P1-R hybrids were isolated. These carry all the essential genes for vegetative phage production and lysogenization including P1 immunity and P1 incompatibility, together with drug resistance genes derived from the R plasmid NR1. In particular, P1Cm and P1CmSmSu derivatives were studied. When strains lysogenic for these phages were induced in the absence of helper phage, yields of phage particles as high as with wild type P1 were obtained. All P1Cm phages isolated were of plaque forming type and usually every plaque contained Cmr lysogens. Lysates of P1CmSmSu lysogens transduced CmrSmrSur at high frequency and they formed plaques with an efficiency of 10-4 to 10-2 per phage particle. Only a minority of these plaques contained drug resistant bacteria. CmrSmrSur transductants isolated from bacteria infected at a high multiplicity with phage P1CmSmSu were lysogens for the original P1CmSmSu. In contrast, CmrSmrSur transductants isolated after infection at low multiplicity appeared to carry the CmrSmrSur markers integrated into the host chromosome. The results described suggest that P1CmSmSu prophages carry the resistance genes transposed into the P1 genome without in principle causing a loss of essential gene functions. However, since these prophages are longer than the wild type P1 genome, the DNA packaged into phage particles has a reduced redundancy which seriously affects the reproduction and lysogenization abilities.