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  • Springer  (156)
  • 2020-2024  (10)
  • 1985-1989  (146)
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  • 1
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    Strategies for differentiation of hiPSCs into dental epithelial cell lineage (2021)
    Springer
    Details
    Publikationsdatum: 2021-07-24
    Print ISSN: 0302-766X
    Digitale ISSN: 1432-0878
    Thema: Biologie , Medizin
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Evidence for high molecular weight Na−Ca exchange in cardiac sarcolemmal vesicles (1988)
    Springer
    The journal of membrane biology 106 (1988), S. 211-218 
    Details
    ISSN: 1432-1424
    Schlagwort(e): Na−Ca exchange ; sarcolemma ; reconstitution ; HPLC ; target sizing ; cardiac
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Cardiac sarcolemma (SL) vesicles were subjected to irradiation inactivation-target sizing analyses and gel permeation high performance liquid chromatography (HPLC) to ascertain the weight range of native Na−Ca exchange. Frozen SL vesicle preparations were irradiated by electron bombardment and assayed for Na−Ca exchange activity. When applied to classical target sizing theory, the results yielded a minimum molecular weight (M r) of approximately 226,000±20,000sd (n=6). SL vesicle proteins were solubilized in 6% sodium cholate in the presence of exogenous phospholipid and fractionated by size on a TSK 30XL HPLC column. Eluted proteins were mixed 1∶1 with mobile phase buffer containing 50mg/ml soybean phospholipid and reconstituted by detergent dilution. The resulting proteoliposomes were assayed for Na−Ca exchange activity. Na−Ca exchange activity eluted in early fractions containing larger proteins as revealed by SDS-PAGE. Recovery of total protein and Na−Ca exchange activity were 91±7 and 68±11%, respectively. In the peak fraction, Na−Ca exchange specific activity increased two-to threefold compared to reconstituted controls. Compared to the elution profile of protein standards under identical column conditions, sodium cholate solubilized exchange activity had a minimumM r of 224,000 Da. Specific45Ca2+-binding SL proteins withM r of 234,000, 112,000, and 90,000 Da were detected by autoradiography of proteins transferred electrophoretically to nitrocellulose. These data suggest that native cardiac Na−Ca exchange is approximately 225,000 Da or larger. The exact identification and purification of cardiac Na−Ca exchange protein(s) remains incomplete.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01872159
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Effects of different sterols on the inhibition of cell culture growth caused by the growth retardant tetcyclacis (1985)
    Springer
    Planta 164 (1985), S. 370-375 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Cell culture and Ga ; Cell division ; Cell suspension culture ; Gibberellin and cell culture growth ; Growth retardant ; Sterol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cell division in cell suspension cultures can be completely blocked by the growth retardant tetcyclacis at a concentration of 10-4 mol l-1. In rice cells it has been demonstrated that the growth inhibition can be completely overcome by application of cholesterol independent of the duration of pretreatment with tetcyclacis. In suspension cultures of maize and soybean, too, the effect of tetcyclacis on cell division was neutralized by adding cholesterol. Other plant sterols, stigmasterol, campesterol and sitosterol were active in a decreasing order. Modifications in the cholesterol perhydro-cyclopentanophenanthrene-ring system indicate that the hydroxyl group at C-3 and the double bond between C-5 and C-6 in ring B are required for the activity. In contrast, gibberellic acid as well as ent-kaurenoic acid could not compensate retardant effects. Likewise, tetcyclasis did not change the level of gibberellins in rice cells as shown by radioimmunoassay. Thus, it is concluded that in cell suspension cultures sterols play a more important role in cell division than gibberellins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00402948
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  • 4
    Digitale Medien
    Digitale Medien
    Genetic variability between two breeds based on restriction fragment length polymorphisms (RFLPs) of major histocompatibility complex class I genes in the pig (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 271-274 
    Details
    ISSN: 1432-2242
    Schlagwort(e): RFLP (restriction fragment length polymorphism) ; MHC (major histocompatiability complex) ; nucleotide diversity ; swine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restriction fragment length polymorphism analyses of SLA class I genes were performed on 55 Duroc and 24 Hampshire boars from the 1986–87 national performance tests of each breed. Few boars were inbred. Southern blotting and hybridization procedures were performed on genomic DNA isolated from white blood cells by using Pvu II, Bam HI, and Eco RI endonucleases and a swine MHC class I probe. Genetic variability within and between the two breeds was estimated in terms of nucleotide diversity, by using a mathematical analysis based on the different RFLP patterns. The nucleotide diversity calculated within each breed was less than that between the two breeds. The results from the nucleotide diversity analysis suggested that genetic variability was greater in the Duroc breed than in the Hampshire breed. A relatively high level of genetic variability was shown in the class I major histocompatibility complex genes in the pig.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266197
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  • 5
    Digitale Medien
    Digitale Medien
    Voltage-dependent channel formation by rods of helical polypeptides (1986)
    Springer
    The journal of membrane biology 93 (1986), S. 111-132 
    Details
    ISSN: 1432-1424
    Schlagwort(e): planar lipid bilayers ; alamethicin ; α-helix dipole ; dipole moment ; voltage-dependent gating ; flip-flop mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The voltage-dependence of channel formation by alamethicin and its natural analogues can be described by a dipole flip-flop gating model, based on electric field-induced transbilayer orientational movements of single molecules. These field-induced changes in orientation result from the large permanent dipole moment of alamethicin, which adopts α-helical conformation in hydrophobic medium. It was, therefore, supposed that the only structural requirement for voltage-dependent formation of alamethicin-type channels might be a rigid lipophilic helical segment of minimum length. In order to test this hypothesis we synthesized a family of lipophilic polypeptides—Boc-(Ala-Aib-Ala-Aib-Ala) n -OMe,n=1–4—which adopt α-helical conformation forn=2–4 and studied their interaction with planar lipid bilayers. Surprisingly, despite their large difference in chain length, all four polypeptides showed qualitatively similar behavior. At low field strength of the membrane electric field these polypeptides induce a significant, almost voltage-independent increase of the bilayer conductivity. At high field strength, however, a strongly voltage-dependent conductance increase occurs similar to that observed with alamethicin. It results from the opening of a multitude of ion translocating channels within the membrane phase. The steady-state voltage-dependent conductance depends on the 8th–9th power of polypeptide concentration and involves the transfer of 4–5 formal elementary charges. From the power dependences on polypeptide concentration and applied voltage of the time constants in voltage-jump current-relaxation experiments, it is concluded that channels could be formed from preexisting dodecamer aggregates by the simultaneous reorientation of six formal elementary charges. Channels exhibit large conductance values of several nS, which become larger towards shorter polypeptide chain length. A mean channel diameter of 19 Å is estimated corresponding roughly to the lumen diameter of a barrel comprised of 10 α-helical staves. Similar to experiments with the N-terminal Boc-derivative of alamethicin we did not observe the burst sequence of nonintegral conductance steps typical of natural (N-terminal Ac-Aib)-alamethicin. Saturation in current/voltage curves as well as current inactivation in voltage-jump current-relaxation experiments are found. This may be understood by assuming that channels are generated as dodecamers but, while reaching the steady state, reduce their size to that of an octamer or nonamer. We conclude that the overall behavior of these synthetic polypeptides is very similar to that of alamethicin. They exhibit the same concentration and voltage-dependences but lack the stabilizing principle of resolved channel states characteristic of alamethicin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01870804
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Effects of mistletoe (Viscum album L.) extracts on cultured tumor cells (1986)
    Springer
    Cellular and molecular life sciences 42 (1986), S. 594-599 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Mistletoe extract ; cytotoxic substances ; hepatoma tissue culture ; human leukemia cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Bacterially fermented mistletoe preparations (BFMP) were tested on rat hepatoma tissue culture (HTC) cells and human leukemia Molt 4 cells. A dose-dependent inhibition of the growth rate of the cells was observed. For both cell lines, cytostatic concentrations, expressed in weight of fresh plant, were 0.5 mg/ml culture medium for oak BFMP and 1 mg/ml for apple tree BFMP. However, the action of the two preparations was markedly different on each cell line. Non-viable HTC cells were not stained by trypan blue while non-viable Molt 4 cells were fully colored by this reagent. A lysis of cellular membranes of HTC cells was observed by electron microscopy. Furthermore, oak BFMP inhibited the growth of virus transformed 3T3-SV40 cells more than that of non-transformed 3T3 cells. In contrast to BFMP, non-fermented extracts and a purified mistletoe lectin showed a greater inhibition of the growth of Molt 4 cells than of HTC cells. Samples withdrawn at different times during fermentation gradually lost their inhibitory effect on the growth of Molt 4 cells while their action on HTC cells increased up to the 4th day of fermentation. These results are discussed in relation to the cytotoxic substances of mistletoe already characterized.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01955552
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  • 7
    Digitale Medien
    Digitale Medien
    Parameterizations of cloud feedback in a radiative-convective model (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 610-623 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Radiative-convective model ; Cloud feedback ; Temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO2 concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO2 doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00877457
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  • 8
    Digitale Medien
    Digitale Medien
    Fermentation and isolation of epidermin, a lanthionine containing polypeptide antibiotic from Staphylococcus epidermidis (1989)
    Springer
    Applied microbiology and biotechnology 30 (1989), S. 219-225 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Staphylococcus epidermidis TÜ 3298/DSM 3095 produces epidermin, a basic 21-residue peptide-amide antibiotic active against aerobic and anaerobic Gram-positive bacteria. Fermentations were performed by batch and feeding processes up to the 2001 scale. Highest yields were obtained when the first purification step was integrated into the fermentation process by on-line adsorption of the antibiotic. Isolation and purification by adsorption chromatography and ion exchange chromatography were performed batchwise.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00256208
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  • 9
    Digitale Medien
    Digitale Medien
    Influence of material design parameters on radiative recombination in GaAs doping superlattices grown by MBE (1985)
    Springer
    Applied physics 37 (1985), S. 83-87 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 73.60 Fw ; 78.55 Ds ; 71.55 Fr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The specific luminescence process in GaAs doping superlattices arises from recombination of electrons populating low-index conduction subbands with holes in the acceptor impurity band across the indirect gap in real space. The luminescence peak energy thus directly reflects the actual value of the tunable gap for the photoexcited state of the superlattice. We have studied the tunability of the effective gap, the recombination rate, and the relative quantum efficiency on superlattice specimen of different material design parameters by means of low-temperature photoluminescence measurements. For optimized design parameters the ratio between luminescence and excitation intensity remains nearly constant over the entire tunability range of the effective gap.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00618857
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  • 10
    Digitale Medien
    Digitale Medien
    Molecular shape and dipole moment of alamethicin-like synthetic peptides (1985)
    Springer
    European biophysics journal 12 (1985), S. 67-73 
    Details
    ISSN: 1432-1017
    Schlagwort(e): Aggregation ; dielectric dispersion ; dipole moment ; molecular shape ; pore former
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract The peptides Boc-(l-Ala-Aib-l-Ala-Aib-l-Ala)n-OMe, with n=2 (P10) and n=4 (P20), have been synthesized as purely hydrophobic models of the antibiotic alamethicin, which is known to be a voltage-dependent pore former in membranes and is apparently α-helical in lipophilic media. These peptides were investigated in 1-octanol, a solvent which resembles the membrane environment. From dielectric dispersion studies quantitative information on the molecular shape and dipole moments could be derived. Further independent data concerning conformation and extent of aggregation of the peptides were obtained by circular dichroism and ultracentrifuge measurements. The results suggest that the peptides assume the form of elongated particles having a significant amount of ordered secondary structure and carrying a dipole parallel to the long axis. Apparently the monomeric peptide molecules undergo, to some extent, a head-to-tail aggregation which is slightly enhanced at lower temperatures. Based on the high-frequency parts of the dielectric dispersion curves the lengths, diameters, and dipole moments of the monomer particles have been determined as 22.5 Å, 10 Å, 36 D (P10) and 28.5 Å, 12 Å, 64 D (P20).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00260429
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