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  • 1
    ISSN: 1432-1424
    Keywords: Noninactivating cardiac Na+ channels ; Removal of inactivation ; Cardiac Na+ channel protein ; α-subunit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Elementary Na+ currents were recorded in inside-out patches from neonatal rat heart cardiocytes to analyze the influence of a site-directed polyclonal anti-serum against the linker region between the domains III and IV (amino acids 1489–1507 of the cardiac Na+ channel protein) on Na+ channel gating and to test whether this part of the α-subunit may be considered as a target for modifying agents such as the (−)-enantiomer of DPI 201-106. Anti-SLP 1 serum (directed against amino acids 1490–1507) evoked, usually within 10–15 min after cytosolic administration, modified Na+ channel activity. Antiserum-modified Na+ channels retain a single open state but leave, at −60 mV for example, their conducting configuration consistently with an about threefold lower rate than normal Na+ channels. Another outstanding property of noninactivating Na+ channels, enhanced burst activity, may be quite individually pronounced, a surprising result which is difficult to interpret in terms of structure function relations. Removal of inactivation led to an increase of reconstructed peak I Na (indicating a rise in NP o) and changed I Na decay to obey second-order kinetics, i.e., open probability declined slowly but progressively during membrane depolarization. The underlying deactivation process is voltage dependent and responds to a positive voltage shift with a deceleration but may operate even at the same membrane potential with different rates. Iodatemodified Na+ channels exhibit very similar properties including a conserved conductance. They are likewise controlled by an efficient, voltage-dependent deactivation process. Modification by (−)-DPI 201-106 fundamentally contrasts to the influence of anti-SLP 1 serum and the protein reagent iodate since (−)-DPI-modified Na+ channels maintain their open probability for at least 120 msec, i.e., a deactivation process seems lacking. This functional difference suggests that the linker region between the domains III and IV of the α-subunit may not be the only target for (−)-DPI 201-106 and related compounds, if at all.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1084
    Keywords: Key words: Liver neoplasms ; Surgery ; Echinococcosis ; Focal nodular hyperplasia ; Hemangioma ; US ; CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of our work was to provide data on the recurrence of resected benign hepatic lesions and to evaluate the value of follow-up examinations in this group of patients. From August to October 1993, 75 patients who had been admitted for liver surgery for benign tumors between 1975 and 1993 were controlled by physical examinations, serological tests, US, and, in the case of equivocal US findings, by CT. The histological diagnoses of the operative specimen included hydatidosis in 43 patients, focal nodular hyperplasia (FNH) in 12 patients, liver cell adenoma in 8 patients, cavernous hemangioma in 8 patients, and congenital cyst in 4 patients. Hepatic scars were observed in 36 of the 75 patients. Four cases of intrahepatic recurrence and 1 case of intraperitoneal spread were observed in the 42 patients with recent hydatosis. Long-term postoperative controls (specific serological tests, US) are necessary in the management of patients with hydatid disease. Follow-up examinations are not indicated in asymptomatic patients who have been operated on for FNH, hemangioma, or congenital cysts.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1017
    Keywords: Key words Single cardiac Na+ channels ; Site-directed antipeptide antibody ; Proteolysis ; Protein reagents ; Calpain ; Stochastic mode switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Failure of inactivation is the typical response of voltage-gated Na+ channels to the cytosolic presence of proteolytic enzymes, protein reagents such as N-bromoacetamide (NBA) or iodate, and antibodies directed against the linker between domains III and IV of the α-subunit. The present patch clamp experiments with cardiac Na+ channels aimed to test the hypothesis that these interventions may provoke the occurrence of non-inactivating Na+ channels with distinct kinetic properties. A site-directed polyclonal antibody (anti-SLP2, target sequence 1481–1496 of the cardiac Na+ channel α-subunit) eliminated fast Na+ inactivation to induce burst activity which was accompanied by the occurrence of two open states. A deactivation process terminated channel activity during membrane depolarization proceeding with time constants of close to 40 ms (at –40 mV). NBA-modified and iodate-modified Na+ channels were kinetically indistinguishable from the anti-SLP2-modified type since they likewise deactivate and, thus, attain an only moderate Po of close to 20%. This is fundamentally different from the behaviour of enzymatically-modified Na+ channels: after cytosolic proteolysis with α-chymotrypsin, trypsin or pronase, mean Po during membrane depolarization amounted to approximately 40% because deactivation operated extremely slowly and less efficiently (time constants 100–200 ms at –40 mV, as a minimum) or was virtually non-operating. In-vitro cleavage of the synthetic linker sequence 1481–1496 confirmed that this part of the α-subunit provides a substrate for these peptidases or reactants for NBA but cannot be chemically modified by iodate. This iodate resistance indicates that iodate-modified Na+ channels are based on a structural alteration of still another region which is also involved in Na+ inactivation, besides the linker between domains III and IV of the α-subunit. Endogenous peptidases such as calpain did not affect Na+ inactivation. This stresses the stochastic nature of a kinetic peculiarity of cardiac Na+ channels, mode-switching to a non-inactivating mode.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 23 (1994), S. 155-165 
    ISSN: 1432-1017
    Keywords: Alamethicin ; Ion channel blockade ; Planar lipid bilayers ; Polycations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The effects of the peptide polycations salmon protamine (M r = 4332,z = + 21) and poly-l-lysine (M r ≅ 100,00,z ≅ + 775) on ion channels formed by synthetic alamethicin Alm-F30 (one negative charge), natural Alm-F50 (neutral) and phosphorylated Alm-F50 (two negative charges) reconstituted in planar lipid bilayers have been studied at the single channel level. It was observed that both polycations in micromolar concentrations transiently block ion permeation through the channels formed by each alamethicin analogue, although in case of the neutral Alm-F50 to a significantly lesser extent. Poly-l-lysine showed to be more effective than protamine in blocking these channels. If either polycation is present in the cis-compartment, blockade occurs only at cis positive membrane voltages. At constant polycation concentration, dwell times in the blocked state increase when salt concentration is lowered, and decrease at acidic pH with an apparent pK of 4.8. Mean lifetime of blockade events shortens when membrane voltage is increased, which suggests that both polycations may permeate through the oligomeric alamethicin channels if conductance levels are 〉 2. We suggest that blockade is caused by electrostatic binding of a single polycation molecule to the C-terminal channel mouth; in case of Alm-F30, Glu18 has to be considered as the putative binding site. Our results provide further evidence for the barrel-stave model and a parallel orientation of dipole monomers in the channel aggregate, the C-termini facing the membrane side with the more positive membrane potential.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 115 (1994), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A highly hydrophilic compound with siderophore activity has been isolated from the supernatant of Staphylococcus hyicus DSM 20459 grown under iron-restricted conditions. The metabolite, named staphyloferrin B, is strictly iron-regulated and produced by a large variety of staphylococci strains. In vivo iron transport measurements and the growth-promoting activity in a bioassay establish staphyloferrin B as the second siderophore for staphylococci besides the previously described staphyloferrin A. The structure elucidation revealed 2,3-diaminopropionic acid, citrate, ethylenediamine and 2-ketoglutaric acid as structural components of the compound. Thus, staphyloferrin B is a structurally new siderophore of the complexone type.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A highly hydrophilic compound was isolated from low iron culture broth of Staphylococcus hyicus DSM 20459 which exhibits siderophore activity to the producer and 37 other staphylococci. The previously unknown metabolite was designated staphyloferrin A and constists of two molecules of citric acid, each linked to d-ornitine by an amide bond. Using an iron-pair HPLC-system we detected staphyloferrin A and a second iron regulated compound (staphyloferrin B) in the culture fluid of several Staphylococcus strains. We found no evidence that staphylococci synthesize catecholor hydroxamate-type siderophores.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 60 (1995), S. 288-289 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 48 (1993), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Studies were conducted to characterize sward dynamics of lucerne (Medicago sativa L.) and perennial, Italian or short rotation hybrid rye-grass (Lolium perenne L. and L. multiflorum Lam.) binary mixtures under hay management. Lucerne/timothy (Phleum pratense L.) mixtures were included as controls. The study was conducted on two farms in central Pennsylvania, USA on Hagerstown silt loams (fine, mixed, mesic hapludalf). Total dry matter yield, grass yield and yield of digestible dry matter were higher for tetraploid perennial and tetraploid Italian ryegrass mixtures than for timothy mixtures. Seasonal production differed for the three kinds of ryegrass. Italian ryegrass dry matter yields were higher in cuts 2 and 3 than perennial ryegrass yields. Grass yields represented 34%, 24% and 12% of total yields of the Italian, perennial or short rotation, and timothy mixtures, respectively. However, herbage in vitro dry matter digestibility of Italian was lower than that of perennial ryegrass.The tetraploid perennial ryegrasses Grimalda and Reveille had high-ranking N concentrations more frequently than other cultivars, while Bar-vestra and Reveille tetraploid perennials and Bison short rotation ryegrass had high-ranking dry matter digestibility values more frequently than the other cultivars. Perennial ryegrass cultivars and Lipo tetraploid Italian ryegrass persisted well for 4 years and produced higher yields with a lower weed content than timothy mixtures. It is concluded that perennial ryegrasses and Lipo Italian ryegrass should be recommended over timothy, as companion grasses with lucerne.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5440-5449 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excess low-frequency noise extending to MHz frequencies was observed in dc current biased granular high-Tc thin films. At particular bias conditions random telegraph signal produced by a single, fast two-level fluctuator dominated the noise properties of the sample. Lifetimes of the low- and high-voltage states of the fluctuating system were found to be exponentially distributed. Power spectra of the excess noise signal could be well fitted with a single Lorentzian contribution. Duty cycle dependence of the random telegraph signal on bias conditions was used to get an insight into physical mechanism causing the fluctuations. Charge trapping events in the intergranular intrinsic Josephson junctions and trapped flux hopping were identified as possible alternative sources of the observed noise.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3029-3031 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectral properties of rf radiation from intrinsic Josephson junctions in high Tc Y-Ba-Cu-O thin film have been measured in the frequency range up to 1.5 GHz. Narrow emission lines with the 3 dB bandwidth of the order of 20 MHz were detected indicating that Josephson clusters radiate coherently. Synchronization conditions are determined by dc current and external magnetic field bias. Frequency locking of radiation to external resonant circuit was also observed. Spectral line narrowing due to resonant lock was distinguished from the coherence-induced narrowing by different tuning properties of the emission line. Noncoherent Josephson radiation manifests itself as a broadband background noise increase. A pronounced 1/f-like tail sensitive to dc bias and magnetic field was observed in a low frequency part of the spectrum.
    Type of Medium: Electronic Resource
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