Showing papers by "University of Basel published in 1982"

Resin development for electron microscopy and an analysis of embedding at low temperature

Abstract: SUMMARY We have tested a wide range of acrylate and methacrylate resin formulations and have concluded that embedding resins can be developed which are usable within a broad range of environmental conditions. To demonstrate this versatility, we have designed two highly-cross-linked resins, one polar and the other nonpolar, that are usable to temperatures from 243 to 223 K. Both of these resins formulations, which are now commercially available, show that systematic experiments can be easily done to study the effects of environmental parameters, such as water content, temperature, or resin polarity, on biological material during embedding. Using these resins and aldehyde-fixed protein crystals, it can be shown that low temperature minimizes the loss of molecular structure to an extent that is not often obtainable with conventional methods of dehydration and embedding. Embedded crystals of aspartate aminotransferase still retained molecular order to 0·6 nm. Embedded crystals of catalase show X-ray diffraction maxima out to 0·8 nm. When sectioned, catalase revealed stain-limited electron and optical diffraction patterns to 2·5 nm. Nevertheless, our work clearly demonstrates that low temperature embedding procedures are superior and that versatile, general purpose resins can be designed to take advantage of this fact.

Protease resistance and conformation of laminin.

Abstract: Laminin, obtained from a tumor basement membrane, was treated with neutral proteases (trypsin, chymotrypsin, elastase, subtilisin, Stuphylococcus aureus protease), which all produced similar fragment patterns upon prolonged digestion. The patterns were different from those obtained for fibronectin, which showed a much higher susceptibility to proteolysis by the same enzymes. Four large fragments could be purified which accounted together for more than half of the mass of laminin. They were found to differ in size, amino acid composition, spectral properties and antigenicity. The largest fragment 1 (Mr 260000-300000) was rich in half-cystine (120 residues/1000) and showed a circular dichroism spectrum indicating the absence of α helix and β structure. Fragment 3 (Mr= 50000) possessed beta; structure and was able to bind onto heparin-Sepharose. Fragments 2 (Mr= 50000) and 4 (Mr= 75000) were related structures and their relative yields depended on the protease used. They showed spectra similar to those of fragment 1. Electron microscopy revealed that fragment 1 consists of three rodlike elements (length 26 nm) connected to each other at one end. The other fragments appeared as globules (fragment 3), short rods (fragment 2) or globules connected to a short rod (fragment 4). Data obtained from limited proteolysis indicated that fragment 1 and 4 (or 2) are in close proximity to each other in the three short arms of laminin, which in its intact form has the shape of an asymmetric cross. The long arm appeared to be readily degraded by proteases. Circular dichroism studies of native laminin indicated about 55%, aperiodic structures, 15%β structure and 30%× helix. The α helix was readily destroyed by proteolysis and showed a sharp, reversible transition at 58° C. Stability of these structures was decreased by reduction of disulfide bonds or by increasing concentrations of guanidine. Heat denaturation rendered laminin susceptible to plasmin, which did not degrade the native protein. Cleavage occurred mainly within the 440000-Mrpolypeptide chain of laminin and was accompanied by a partial loss of the long arm.

On the geometry of conjugacy classes in classical groups

Abstract: We study closures of conjugacy classes in the Lie algebras of the orthogonal and symplectic groups and determine which ones are normal varieties. Furthermore we give a complete classification of the minimal singularities which arise in this context, i.e. the singularities which occur in the open classes in the boundary of a given conjugacy class. In contrast to the results for the general linear group ([KP1], [KP2]) there are classes with non normal closure; they are branched in a class of codimension two and give rise to normal minimal singularities. The methods used are (classical) invariant theory and algebraic geometry.

Specimen preparation for electron microscopy using low temperature embedding resins

Abstract: SUMMARY Studies using polar and non-polar methacrylate-based resins (Lowicryl® K4M and HM20) suitable for low temperature embedding are described. We present the first applications of the system to various membrane structures in glutaraldehyde-fixed, uranyl acetate-stained thin sections of bacteria, mitochondria and cell-cell contact regions.

Antiferromagnetic long-range order in the anisotropic quantum spin chain

Abstract: This is a study of the ground-state properties of the one-dimensional spin-s (12⩽s<∞) anisotropic XYZ antiferromagnet in a magnetic field of arbitrary direction. It provides the first rigorous results for the general case of this model in non-zero field. By exact calculations we find the existence of an ellipsoidal surface h = hN in field space where the ground state is of the classical two-sublattice Neel type with non-zero antiferromagnetic long-range order. At hN there are no correlated quantum fluctuations. We give upper and lower bounds for the critical field hc where antiferromagnetic long-range order is suppressed by the field. The zero-temperature phase diagrams are discussed for a few representative cases.

Intracellular transport of microinjected 5S and small nuclear RNAs

Abstract: The mechanism by which some RNAs are segregated in the cell nucleus was analysed by microinjecting 32P-labelled total RNA from HeLa cells into the cytoplasm of Xenopus oocytes. Small nuclear RNAs (U1, U2, U4, U5 and U6) migrated into the cell nucleus, where they became 30–60 fold more concentrated than in the cytoplasm. Other RNAs, such as tRNA and 7S RNA, remained in the cytoplasm, while 5S RNA became concentrated in the nucleolus. Studies with lupus erythematosus antibodies showed that the migrating RNAs become associated with oocyte RNA-binding proteins.

Larger foraminifera, giant cells with a historical background

Abstract: The history of foraminifera as recorded by the shell of numerous taxa illustrates the repetitive rise of benthic, large-sized K-strategists throughout geologic time. The phylogeny reconstructed by methods of comparative anatomy and supported by biostratigraphic distribution permits to identify analogous shell structures pointing to functions of the living cell. The shell registers autecological adaptation, ontogeny, protoplasmic streaming patterns, protoplasmic differentiation and patterns of differentiation at the cell surface. The high potential of shell regeneration points to the functional importance of shell shape during the long vegetative life and documents experiments performed by nature itself. The extended knowledge of their history, their size and their natural recording device in their shell predestines the foraminifera as experimental system to explore the performances of free-living single cells and many mechanisms regulating their life.

Supernova statistics and related problems

Abstract: In the following the frequencies of SNe in external galaxies (Section 1) and in our Galaxy (Section 2) are discussed. The galactic frequencies are compared with SNRs, pulsars, and white dwarfs. In Section 3 the absolute maximum magnitudes of SNeI and SNeII are discussed, as well as the evidence of SNeI being good standard candles. Speculations on the progenitors of SNe in Section 4 are consistent with the assumption that SNeI come from stars with masses > 8 M ⊙, while SNeI could come from accreting white dwarfs in close binary systems.

Senile dementia of Alzheimer type: astroglial reaction to extracellular neurofibrillary tangles in the hippocampus. An immunocytochemical and electron-microscopic study.

Abstract: Two types of Alzheimer neurofibrillary tangles may be found in the hippocampus in senile dementia of the Alzheimer type. Besides classical flame-shaped intraneuronal tangles, there are less compact tangles representing extracellular remnants of destroyed neurons with neurofibrillary change. Strong immunoreactivity for glial fibrillary acidic protein (GFA) was found in the second type of tangles, which was due to penetration of fine processes of fibrous astrocytes into bundles of paired helical filaments (PHF). PHF appear to be a strong stimulus for astrocytic reaction when they are not segregated from the neuropil by the neuronal cell membrane.

Molecular characterization of ribonucleoprotein antigens bound by antinuclear antibodies. A diagnostic evaluation.

Abstract: The specificity of antinuclear antibodies in sera from 54 patients with various rheumatic diseases was analyzed by immunoprecipitation of 32P- or 35S-methionine-labeled HeLa cell extracts. Of 35 sera giving a speckled and/or homogeneous immunofluorescence pattern in rat liver nuclei, 20 contained antibodies to nuclear ribonucleoproteins, which are defined by their ribonucleic acid and protein components. Four sera reacted with a nuclear antigen (Ga) which has not been described so far. Of 19 sera with antinucleolar antibodies, 18 did not react with nuclear or nucleolar ribonucleoproteins. Correlation of these molecularly defined antinuclear antibody specificities with immunofluorescence patterns and rheumatic diseases is discussed.

Is the Shell-Model Concept Relevant for the Nuclear Interior?

Abstract: The $3s$ radial wave function $R(\mathcal{r})$ has been determined by electron scattering from $^{206}\mathrm{Pb}$ and $^{205}\mathrm{Tl}$. The shape of $R(\mathcal{r})$ in the central region of the nucleus is used to test the validity of the independent-particle shell model at large nuclear density.

Short-term Naloxone Administration in Schizophrenic and Manic Patients: A World Health Organization Collaborative Study

Abstract: • A double-blind study of the behavioral effects of short-term naloxone hydrochloride administration was performed in 32 schizophrenic and 26 manic patients in a World Health Organization collaborative project. There was a significant naloxoneassociated reduction in overall physician-rated symptoms in schizophrenic patients concurrently treated with neuroleptic medication (N = 19) but not in medication-free schizophrenics (N = 13). Physician ratings of auditory hallucinations showed significant naloxone-associated improvement for the total schizophrenic population, while self-ratings of auditory hallucinations showed improvement only in neuroleptic-treated schizophrenics. While further studies are needed to delineate these effects as to clinical significance, they may bear etiological implications for the psychobiology of schizophrenia, including the possibility of synergistic effects of dopamine and endorphin blockade. Naloxone produced no significant behavioral effects in manic patients. These findings are discussed with relationship to the hypotheses of endorphin involvement in schizophrenia and mania.

Greater Antihypertensive Efficacy of the Calcium Channel Inhibitor Verapamil in Older and Low Renin Patients

Abstract: 1. The calcium slow channel inhibitor verapamil was administered as monotherapy (240-270 mg; mean 427 mg/day) on the average for 93 days to 43 patients with essential hypertension; 11 with low, 24 with normal and eight with high renin sodium index. 2. Verapamil reduced blood pressure from 171 ± 16/108 ± sd 6 mmHg to 152 ± 14/93 ± 9 (both P 3. The fall in mean blood pressure after verapamil was directly related to age ( r = 0.759, P P r = 0.400, P r = −0.551), P 4. This greater blood pressure decrease with verapamil in older and low renin patients suggests a greater calcium influx-dependent vasoconstriction in these patients, which seems to be directly related to the activity of the sympathetic nervous system.

Molecular cloning of the white locus region of Drosophila melanogaster using a large transposable element.

Abstract: We report the molecular cloning of a chromosome segment including the white locus of Drosophila melanogaster. This region was isolated using a deficiency extending from the previously cloned heat-shock puff sequences at 87A7 to a large transposable element containing the loci white and roughest.FB-NOF, a 7.5 kb element with partial homology to a family of inverted repeat sequences (Potter et al., 1980), is found very near the deficiency breakpoint, and is followed by DNA originating from the white locus region. Sequences totalling 60 kb surrounding this initial entry point were obtained by the cloning of successively overlapping fragments from a wild-type strain. Several rearrangement breakpoints have been mapped relative to the cloned DNA; these define the limits of the white locus and further differentiate the "white proximal region", thought to function in gene regulation, from the remainder of the locus. Insertion of the dispersed repetitive element copia into the white locus is observed in strains carrying the white-apricot allele. Analysis of several white-apricot revertants suggests that copia insertion is responsible for the apricot eye color phenotype.

Purification and Characterization of the Cytochrome c Oxidase from Rhodopseudomonas sphaeroides

Abstract: When grown aerobically in the dark, Rhodopseudomonas sphaeroides develops a respiratory chain similar to that in mitochondria and the photosynthetic apparatus is suppressed. The aa3-type cytochrome c oxidase from Rps. sphaeroides has been purified in Triton X-100 by affinity chromatography with Sepharose 4B coupled to yeast cytochrome c. The oxidase contains 14 nmol heme a/mg protein and is composed of three polypeptide subunits with relative molecular masses of 45000, 37000 and 35000. The enzyme is highly active in the presence of detergents, with a maximal velocity of 300s−1/mol oxidase using either yeast or horse-heart cytochrome c. The Rps. sphaeroides oxidase is cross-reactive with antibodies directed against the oxidases from Paracoccus denitrificans and Saccharomyces cerevisiae. A particularly close relationship is indicated in the case of P. denitrificans. The Rps. sphaeroides oxidase has been incorporated into phospholipid vesicles. The resulting oxidase in these vesicles demonstrates high enzymatic activity and a respiratory control ratio of 5. Using these vesicles, no evidence for proton extrusion accompanying cytochrome c oxidation was observed. The data suggest that the Rps. sphaeroides oxidase does not function as a proton pump.

The BtuB Group Col Plasmids and Homology Between the Colicins They Encode

Abstract: Colicins A, E1, E2, E3, E4, E5, E6, and E7 exhibited reduced activity against BtuB mutants of Escherichia coli K-12 and also against wild-type cells in the presence of vitamin B12. Plasmids encoding representatives of these colicins were specifically immune to high levels of the homologous colicin. Col + cells grown in media containing mitomycin C accumulated large amounts of colicin polypeptide. ColE2 + , ColE3 + , ColE4 + , ColE5 + , and ColE6 + cultures also synthesized large amounts of second, lower-molecular-weight protein under these conditions. Colicins E2 through E7, but not A or E1, reacted with antiserum raised against purified colicin E3. Colicins E2 and E7 induced synthesis of β-galactosidase encoded by lacZ under the control of the colicin Ib gene promotor on a derivative of Col plasmid ColIb.P9. This promotor is usually active only when the cells are treated with agents which damage DNA or block replication. Plasmids encoding various mutant forms of colicin E3 (M. Mock and M. Schwartz, J. Bacteriol. 142: 384-390, 1980) recombined with ColE2, ColE4, ColE5, or ColE6 plasmids at a frequency of 10 −4 per cell to produce a colicin active against ColE2 + , E4 + , E5 + , or E6 + cells. ColE5 and ColE6 plasmids recombined with ColE3 plasmids bearing mutations affecting colicin E3 receptor recognition, envelope penetration, and catalytic activities. ColE2 and ColE4 plasmids recombined only with ColE3 plasmids bearing mutations affecting receptor recognition and envelope penetration. Recombinants between mutant ColE3 plasmids and ColA, ColE1, or ColE7 plasmids were not detected. We propose the designation BtuB group for the colicins described here, and we divide the group into two classes comprising colicins A and E1, which act on the cytoplasmic membrane, and the related colicins E2 through E7, which have known or putative nuclease activities. Images

Intraindividual variability in theophylline pharmacokinetics: Statistical verification in 39 of 60 healthy young adults

Abstract: After administering a single 300 mg dose of theophylline in oral solution to 12 healthy adults, the dose-normalized area under the plasma concentration-time curve was 97.2±20.1 % (mean±SD) of that after giving a 500 mg dose and statistically indistinguishable. Similarly, these areas multiplied by the individual's terminal disposition rate constant (β) were statistically indistinguishable between 300 and 500mg doses (99.1±10.3%), giving no evidence of dose-dependence for theophylline kinetics at the levels below 15 μg/ml observed in these individuals. After an intravenous dose, a shortlived distribution phase (t1/2α) is sometimes seen. An a phase, however, is hardly discernible in over 250 profiles arising from oral doses administered during five single dose bioavailability studies. Almost all such profiles appear to follow single-compartment model predictions. With precautions to avoid a potential a phase, a terminal log-linear slope can be fitted by least squares analysis with a relative standard error in the slope determination almost always less than 6%. Covariance analysis confirms statistically that 39 of the 60 participating individuals varied in their β on the different occasions each was required to take a dose during the course of a crossover bioavailability trial. In one study, even though each individual was observed on only two occasions, 9 out of 12 showed statistically identifiable variation in β. Fluctuations in β of 60% can be seen. Changes of 30% or greater are common and can occur within 3 or 4 days. Thus real, large, and potentially frequent changes in β of theophylline have been identified in a majority of normal subjects. These changes do not appear to be confined to either sex, to smokers or nonsmokers, or to heavier or lighter individuals. No chronological pattern has, as yet, been recognized in the intraindividual variability in β.

Procollagen N-proteinase. Properties of the enzyme purified from chick embryo tendons.

Abstract: Procollagen N-proteinase was purified about 3700-fold from chick embryo tendons. Electrophoresis of the protein after iodination and denaturation suggested it was homogeneous. However, the native enzyme could not be examined by gel electrophoresis, and therefore homogeneity of the preparation was not conclusively established. Antibodies to the enzyme completely inhibited activity and gave a single precipitant line by double immuno-diffusion. The Km for a native procollagen substrate was 0.3-0.5 microM. The same protein after denaturation inhibited activity. The enzyme did not cleave type III procollagen from human fibroblasts or a type IV procollagen from a mouse sarcoma. Ca2+ was required for maximal enzymic activity. The data suggested a second metal requirement, but this was not identified. Reducing agents and metal chelators inhibited activity, but there was little if any inhibition from several inhibitors of other neutral metalloproteinases.

Kink instability in planar ferromagnets

Abstract: The 360\ifmmode^\circ\else\textdegree\fi{} screw kinks in a planar ferromagnet with an in-plane magnetic field are unstable above a critical-field strength. We show that this critical-field strength decreases rapidly as the kink velocity increases toward its maximum value. As a consequence, square-root singularities appear in the dynamic structure factor $S(q,\ensuremath{\omega})$ at field-dependent cutoff values of $\frac{\ensuremath{\omega}}{q}$.

The contribution of fungal enzymes to the digestion of leaves by Gammarus fossarum Koch (Amphipoda)

Abstract: Gut extracts of Gammarus fossarum liberated reducing substances (at pH values ≤7) and amino acids (pH≥7) from freshly shed oak leaves only after removal of soluble leaf phenols. When carboxymethylcellulose was used at a concentration equal to that of leaf cellulose, release of reducing substances was considerably higher. Fungal enzymes extracted from decomposing leaves were active against structural carbohydrates but showed no proteolytic activity. At low pH values, they retained their full activity in the presence of gut enzymes of G. fossarum, at higher pH values they were inhibited. Conditioned leaves released larger amounts of reducing substances and amino acids when exposed to gut enzymes. The improvement varies with the fungal species used for conditioning and with the length of the conditioning period. The digestibility of leaf carbohydrates and proteins reached separate peaks and then declined. Fungal carbohydrases ingested by G. fossarum retained some activity for up to 4h.