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  • Articles  (111)
  • 1995-1999  (103)
  • 1960-1964  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 167 (1996), S. 539-547 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bovine pulmonary arterial endothelial cells (BPAEC) were grown on permeable polycarbonate membrane filters suspended between two compartments representing the blood vessel lumen and the interstitium. This in vitro model of an endothelium was subjected to a battery of tests to unravel the mechanisms of zinc transport from the blood into peripheral tissues. Transport of 65Zn across BPAEC from media containing zinc concentrations up to 50 μmol/L exhibited both saturable and nonsaturable kinetics. Vmax of the saturable component was 246 ± 43 pmol/(h × cm2) and Km was 2.3 ± 1.3 μmol/L. Transport was pH and temperature sensitive and substantially influenced by albumin and histidine concentrations, but not influenced by analogous minerals or metabolic inhibitors. Inhibition of coated vesicle formation by depletion of intracellular potassium reduced 65Zn transport. Albumin carrying a zinc ion crossed the endothelium more rapidly than zinc-free albumin. When evaluated together, this body of evidence supports the existence of two major pathways of zinc transport across the pulmonary endothelium, but neither involves entry into the endothelial cells. One pathway involves receptor-mediated cotransport with albumin by transcytotic vesicles. The other is nonsaturable and involves cotransport with albumin and low molecular weight ligands, principally histidine, through intercellular junctions and nonselective, bulk-fluid transcytosis. © 1996 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 845-845 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 1 Ill.
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  • 3
    ISSN: 1573-5176
    Keywords: alginate ; pilot plant process ; pre-extraction ; Macrocystis pyrifera ; acid treatment ; formalin treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the extraction of alginate from brown seaweeds, the acid pre-extraction treatment has been considered by many authors as an essential step because it makes the alginate more readily soluble in an alkaline solution. At pilot plant level, extractions were made (i) using formalin treatment prior to the acid pre-extraction treatment (ii) using different acid treatments so the calcium ions exchanged varied from 83% to 4%. The use of formalin treatment gave a product with less color. During the acid pre-extraction treatment, it was possible to reduce the calcium exchanged from 33.4% to almost zero with a maximum reduction in alginate yield of 7%. The degree of acid treatment was positively correlated to calcium exchanged and yield but negatively correlated with alginate viscosity. Using strong acid conditions the viscosity was 168 mPa s, while mild acid conditions produced an alginate with 623 mPa s. The direct extraction from calcium alginate to sodium alginate is possible because strong alkaline conditions were used, pH 10 at 80 °C for two hours and with a low water volume. The best pre-extraction treatment to obtain an alginate with high viscoity is to hydrate the alga with 0.1% formalin overnight, then wash the alga once with hydrochloric acid at pH 4 using a batch system with continuous agitation during 15 min.
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  • 4
    ISSN: 1573-5176
    Keywords: Alginate ; pilot plant process ; extraction ; Macrocystispyrifera ; filtration ; centrifugation ; flocculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of temperature (70, 80, 90 °C) and time (1–9 h) during the alkaline extraction step on alginate yield and quality were studied. The alginate yield increased with time and maximum yield was obtained after 3.5 h treatment, ranging from19.4% at 70 °C to 21.9% at 90 °C. The viscosity of the alginate produced was inversely correlated with the temperature and time. At70 °C the slope of the curve was almost zero(753 to 923 mPa s); at 90 °C the viscosity loss was 154 mPa s per hour during the first two hours, reducing from 523 to 86 mPa s after 5 h; 80 °C yielded values between those for 70 °C and90 °C. The best conditions for alkaline extraction were using pH 10 at 80 °C for two hours. The curves obtained gave useful information for controlling the viscosity of the alginate during production. It was found that viscosity of the paste formed during alkaline extraction (`process viscosity') was the best parameter to determine there action rate during extraction. Alginate yield increased during filtration time from 17.6% to 23.7%after 55 min at 70 °C. In this step the viscosity of the alginate obtained remained almost constant (522–610 mPa s), indicating no degradation of the products during filtration. The best dilution to filter the alginate extract was obtained at 45 mPa s. Diatomaceous earth (Celite) and expanded lava(Perlite) were tested as filter aids. Expanded lava was the best filter aid, using 1 kg per kilogram of alginate produced. Three methods were studied to separate the alkaline-insoluble residues after extraction: filtration, centrifugation, flocculation, and combinations of them. The best system found was filtration with flocculant in a rotary vacuum filter, with a knife advance of 0.1 mm every 3.5 seconds and drum rotation of 2 rpm, yielding an average filtration flow rate of 10.5 L min-1.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; DNA ; Mitochondrial DNA ; Forensic DNA typing ; Polymerase chain reaction analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The polymorphic control region of mitochondrial DNA (mtDNA) is becoming more commonly used in forensic applications to differentiate among individuals in a population. Two hypervariable regions (HV1 and HV2) are often sequenced following amplification of the mtDNA via the polymerase chain reaction (PCR). More rapid screening assays would reduce both the effort and the expenses of comparing two samples. A methodology has been developed that first uses restriction endonuclease digestion of the PCR-amplified mtDNA using RsaI and Mn/I and then capillary electrophoresis (CE) to separate and size the PCR-RFLP fragments. This rapid procedure offers an alternative method for screening of polymorphisms in amplified mtDNA samples. In addition, the presence of a T→C transition at position 16189, which gives rise to the so-called “C-stretch” in HV1, may be predicted from the presence of nonspecific PCR products in the CE results.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0173-0835
    Keywords: Trypanosoma brucei ; Free-flow electrophoresis ; Endosomes ; Lysosomes ; Transferrin ; Percoll ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In this paper we demonstrate the power of preparative free-flow electrophoresis (FFE) for the study of endocytosis by African trypanosomes. Endocytosis of extracellular macromolecules by these parasites occurs through a specialized region of the parasite called the flagella pocket. The uptake of fluid phase markers such as horseradish peroxidase (HRP) into the various compartments of the endocytic pathway of bloodstream forms of Trypanosoma brucei brucei was manipulated by regulating the external environment (e.g., by altering the temperature of incubation). The various subcellular compartments were then separated by free-flow electrophoresis (FFE) or isopycnic density gradient centrifugation and analyzed for marker uptake. At low temperatures, HRP was found predominantly in the flagellar pocket. Increasing the temperature resulted in a time-dependent uptake of HRP into more positively charged endosomal fractions. However, little HRP activity was detected in lysosomal compartments, suggesting that either HRP had not yet entered the lysosome or was degraded immediately upon entry. Through the use of FFE we were able to identify and analyze compartments of the endosomal pathway that were not possible to identify by density gradient centrifugation alone. Although the differences in FFE separation of the endocytic compartments as seen in HRP uptake were striking, the minor changes seen within the lysosomal system were more subtle, as depicted in the protease profiles. In conlusion, we show that preparative FFE is a powerful technique for the analysis and separation of flagellar pocket-derived membranes from other endosomal and lysosomal compartments of African trypanosomes.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic spectrum of germylidene (H2C(Double Bond)Ge), the simplest unsaturated germylene, has been observed for the first time. Jet-cooled H2CGe and D2CGe were produced by an electric discharge through tetramethylgermane diluted in argon at the exit of a supersonic expansion. High-resolution spectra of H2C74Ge and D2C74Ge, obtained from (CH3)4〈sup ARRANGE="STAGGER"〉74Ge prepared from isotopically enriched 74Ge metal, have been rotationally analyzed to yield the following r0 structures: r0″(CGe)=1.7908(2) Å, r0″(CH)=1.1022(5) Å, θ0″(HCH)=115.05(5)°, r0′(CGe)=1.914(4) Å, r0′(CH)=1.082(9) Å, and θ0′(HCH)=139.3(11)°. The 367–354 nm B˜1B2–X˜ 1A1 band system consists of prominent perpendicular bands involving the CGe stretching (ν3) and CH2 scissors (ν2) vibrations and a weaker series of vibronically induced parallel bands involving the CH2 rocking mode (ν6). Vibronic bands involving Δv=2 changes in ν6(b2) and ν4(b1) have also been assigned. The fluorescence decays of single rotational levels of the 000 band of H2C74Ge exhibit molecular quantum beats for about 70% of the levels surveyed. Density of states arguments reveal that most of the beats originate from interactions with high rovibronic levels of the ground state. In one case, hyperfine splittings in the Fourier transform of the beat pattern indicate an accidental coincidence with an excited triplet state level. The less frequent occurrence of quantum beats in germylidene compared to silylidene, where they are almost universal, can be attributed to the smaller density of ground state levels at the zero-point energy of the S2 state in the former. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9300-9305 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monoiodogermylene has been detected for the first time using pulsed discharge and laserinduced fluorescence techniques. HGeI and DGeI were produced by an electric discharge through argon seeded with H3GeI or D3GeI. Although the vibronic structure in the spectra was very limited, all three excited state vibrational frequencies have been obtained for both isotopomers. Analysis of the partially resolved rotational structure of the 000 bands gave the following approximate r0 structures, with the bond angles constrained to previous ab initio values: r0″(Ge–I)=2.525(10) Å, r0″(H–Ge)=1.593(15) Å, θ0″(HGeI)=93.5°, r0′(Ge–I)=2.515(10) Å, r0′(H–Ge)=1.618(15) Å, and θ0′(HGeI)=116.2°. The fluorescence lifetime of monoiodogermylene in the lowest rovibronic levels is 1.515±0.004 μs and shows significant variations on deuteration and with rotational and vibrational level. © 1998 American Institute of Physics.
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  • 9
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Motivated by our recent finding that the singlet–triplet bands of selenoformaldehyde involve an upper state with large zero field splittings, we have extended the theory and written a program for predicting and fitting such rotationally resolved spectra. Triplet state matrix elements for a case (A) basis have been developed, including corrections for centrifugal and spin–centrifugal distortion. The full Hamiltonian matrix has been symmetry adapted, simplifying the problem to four individual matrices of approximately equal size for molecules of orthorhombic symmetry. Diagonalization of these matrices yields triplet state energies that are in agreement with previous treatments using a basis in which the spin splittings are small relative to the rotational intervals. Methods have been developed for sorting the eigenvalues and assigning quantum labels regardless of the magnitude of the spin splittings. The calculation of the relative intensities of the rotational lines within a band has been programmed using transition moment matrix elements from the literature. The selection rules for various upper state symmetries have been developed in a form useful for the analysis of spectra. Band contour predictions of spectra for various coupling cases have been presented. © 1995 American Institute of Physics.
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  • 10
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution laser induced phosphorescence spectra of the 820 nm band system of selenoformaldehyde have been recorded with Doppler-limited resolution. Rotational analysis of the 000 bands of D2C80Se, H2C78Se, and H2C80Se revealed only P, Q, and R branches obeying ΔKa=0 selection rules with no evidence of spin splittings. However, these bands show pronounced Zeeman broadening which is linearly dependent on the upper state J value. These results are interpreted as the consequences of case (ab) coupling in the a˜ 3A2 state, in which there is a large zero field splitting due to substantial mixing of two of the spin components with the nearby 3A1(π,π*) state. The only other asymmetric top molecule known to exhibit case (ab) coupling in the triplet state is carbon disulfide. © 1995 American Institute of Physics.
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