Showing papers by "Humboldt University of Berlin published in 1992"
TL;DR: A simple-to-perform synthesis yielded a conjugate suitable for use as a tracer in immunoassays for cortisol measurement and showed excellent correlation with a commercially available radioimmunoassay adapted for salivary cortisol measurement.
837 citations
TL;DR: Different parameters are defined which permit to assess the quality of an immunoassay and which should be used in routine assays as internal controls in the laboratory, and different EIA variants to detect specific antibodies are reviewed.
442 citations
TL;DR: To identify components of the mammalian endoplasmic reticulum involved in the translocation of secretory proteins, crosslinking and reconstitution methods were combined and a multispanning abundant membrane glycoprotein was found which is in proximity to nascent chains early in translocation.
Abstract: To identify components of the mammalian endoplasmic reticulum involved in the translocation of secretory proteins, crosslinking and reconstitution methods were combined. A multispanning abundant membrane glycoprotein was found which is in proximity to nascent chains early in translocation. In reconstituted proteoliposomes, this protein is stimulatory or required for the translocation of secretory proteins.
311 citations
31 Jan 1992
TL;DR: Biaxial, alphanumeric classification of primary care problems and related actions and 17 chapters [A-Z]: body systems.
Abstract: Biaxial, alphanumeric classification of primary care problems and related actions 17 chapters [A-Z]: body systems Components in each chapter: symptoms and complaints [01-29] diagnostic / screening / preventive services [30-49] medication / treatment / procedures [50-59] test results [60,61] administrative [62] referrals, other reasons for encounter [63-69] specific diagnoses [70-99]
299 citations
TL;DR: The stochastic differential equation is a generalization of Langevin's equation as discussed by the authors, which is obtained if b = 0. Necessary and sufficient conditions on a, b and r are given under which a stationary so...
Abstract: The stochastic differential equation is a generalization of Lange-vin's equation, which is obtained if b = 0. Necessary and sufficient conditions on a, b and r are given under which a stationary so...
163 citations
TL;DR: In this article, a traveling-wave-driven electrohydrodynamic micropump without moving parts is discussed, and the fundamental operating principles, such as highfrequency traveling waves, a self-stabilizing temperature gradient, and increased wave number, are outlined.
Abstract: A traveling-wave-driven electrohydrodynamic micropump without moving parts is discussed. The fundamental operating principles, such as high-frequency traveling waves, a self-stabilizing temperature gradient, and increased wave number, are outlined. The main advantages of the realized pump are its ability to move conductive liquids such as water and weak electrolyte solutions, the lack of any movable parts, and integration. A microfabricated structure demonstrating the pump operation is outlined, and quantitative results are described. Typical parameters characterizing the advantages and limitations of the pumping principle are discussed. Perspectives for optimization of the realized micropump can be seen in further miniaturization and increased number of electrodes. Possible applications are biological, medical, and chemical devices that can deliver accurately metered quantities of fluids in the nl/min and mu l/min range. >
143 citations
TL;DR: The theoretical model elaborated in this paper is in good agreement with experimental results obtained in microfabricated chambers of linearly arranged electrodes and explains the behavior of homogeneous cellulose spheres as well as that of membrane‐covered pine polls.
Abstract: The traveling-wave-induced linear transfer of dielectric particles like living cells and artificial objects of microscopic dimensions is analyzed. It is shown that the electrode geometries must correspond to particle sizes to allow an effective manipulation of particles immersed in weakly electrolytic solutions by high frequency traveling waves. The theoretical model elaborated in this paper is in good agreement with experimental results obtained in microfabricated chambers of linearly arranged electrodes. It explains the behavior of homogeneous cellulose spheres as well as that of membrane-covered pine polls. The traveling-wave-driven electrodes are described by a superposition of time-dependent point charges. Subsequently, each of these point charges has to be considered as polarizing the dielectric particle and interacting with the polarized particle. This results in forces which effectively translocate the particle.
137 citations
TL;DR: It appears to be possible to move and rotate cells or particles at will using very-high-frequency fields and media of increased relative permittivity, as shown by experimental data on levitation and rotation.
132 citations
TL;DR: An upper bound for in terms of computation of integer determinants is given from which it is concluded that all logspace counting classes are contained in.
Abstract: We refine the techniques of Beigelet al. [4] who investigated polynomial-time counting classes, in order to make them applicable to the case of logarithmic space. We define the complexity classes
and demonstrate their significance by proving that all standard problems of linear algebra over the finite ringsZ/kZ are complete for these classes. We then define new complexity classes LogFew and LogFew
and identify them as adequate logspace versions of Few and Few
. We show that LogFew
is contained in
and that LogFew is contained in
for allk. Also an upper bound for
in terms of computation of integer determinants is given from which we conclude that all logspace counting classes are contained in
.
124 citations
01 Jan 1992
TL;DR: In this article, sufficient and necessary conditions for the convergence of Newton's method based on generalized derivatives are presented, which require uniform injectivity of the derivatives as well as uniform high-order approximation of the original locally Lipschitz function along rays through the solution.
Abstract: This paper presents sufficient and necessary conditions for the convergence of Newton’s method based on generalized derivatives. These conditions require uniform injectivity of the derivatives as well as uniform high-order approximation of the original locally Lipschitz function along rays through the solution. Our approach permits to determine approximate solutions of the Newton subproblems and to use such concepts of derivatives for nonsmooth functions, multivalued or not, as directional and B-derivatives, contingent derivatives, generalized Jacobians and others. Furthermore, we ensure solvability of the subproblems via surjecivi-ty of the derivatives and verify a Kantorovich-type convergence theorem.
107 citations
TL;DR: It is concluded that the Vpu protein is phosphorylated by the ubiquitous CKII in HIV-1-infected human host cells.
Abstract: Vpu as a human-immunodeficiency-virus-type-1-encoded 81-amino-acid integral-membrane protein was expressed in Escherichia coli using the inducible ptrc promoter of an ATG fusion vector. Recombinant Vpu is associated with membranes of E. coli and could be partially solubilized by detergents. Recombinant Vpu was phosphorylated in vitro with purified porcine casein kinase II (CKII) as well as with a CKII-related protein kinase found in cytoplasmic extracts of human and hamster cells. Recombinant Vpu associated with E. coli membranes has turned out to be the best substrate for in vitro phosphorylation with CKII. This reaction can be inhibited by heparin and the ATP analogue 5,6-dichloro-1-(β-D-ribofuranosyl)benzimidazole (DRB), both known to be potent inhibitors of CKII. Radiolabelled γATP and γGTP were used as phosphate donors for in vitro phosphorylation of recombinant Vpu. In vivo phosphorylation of Vpu-1-infected H9 cells was also inhibited by DRB. We concluded therefrom that the Vpu protein is phosphorylated by the ubiquitous CKII in HIV-1-infected human host cells.
Two seryl residues in the sequence of Vpu (position 52 and 56) correspond to the consensus s/TXXD/E for CKII. These potential phosphorylation sites are located within a well-conserved dodecapeptide of Vpu (residues 47–58), which is found in different HIV-1 strains as well as in a Vpu-like protein of SIVCPZ.
Monoclonal and polyclonal antibodies directed against two different epitopes of Vpu were used for immunoprecipitation of Vpu from HIV-1-infected cells and for detection of Vpu in Western blot analyses. Vpu from HIV-1-infected cells as well as recombinant Vpu expressed in E. coli were determined by SDS/PAGE using 6 M urea to be 9 kDa, which corresponds to the calculated molecular mass of Vpu.
TL;DR: Data indicate that interferon treatment is frequently associated with the simultaneous fall in titer of viral DNA by several orders of magnitude and the emergence of novel pre-C sequences, some of them preventing HBeAg expression, however, the presumably immune-mediated selection for pre- C mutant viruses and decrease in viremia under interferons treatment appears not to be prognostic for successful or unsuccessful virus elimination.
01 Jan 1992
TL;DR: The data presented suggest an involvement of lipid peroxidation in the pathogenesis of atherosclerosis and indicate that the majority of the oxygenation products are formed via nonspecific, non-enzymatic reactions possibly initiated by the action of a 15-lipoxygenase.
Abstract: Oxidative modification of low density lipoproteins and tissue lipids has been proposed to be involved in the pathogenesis of atherosclerosis. We examined human atherosclerotic lesions of various stages from fifteen victims of acute heart failure and detected substantial amounts of oxygenated fatty acids in the tissue ester lipids. The degree of lipid oxygenation correlated with the stage of advancement of the lesion. More than 85% of the oxygenated fatty acids were localized in the cholesterol esters, whereas phospholipids contained only small amounts. Structure elucidation of the oxygenation products indicated a nonspecific product pattern of various isomers of keto- and hydroxy-octadecadienoic acid. The data presented suggest an involvement of lipid peroxidation in the pathogenesis of atherosclerosis and indicate that the majority of the oxygenation products are formed via nonspecific, non-enzymatic reactions possibly initiated by the action of a 15-lipoxygenase.
TL;DR: The results show that RFLP analysis may be used to re-classify the Trichoderma aggregate, and contradict the claim that T. reesei is a subspecies of T. longibrachiatum.
Abstract: We have analyzed nine different species of the filamentous fungus Trichoderma and three strains of T. reesei for the presence of hypervariable loci in their genomes by hybridization with simple repeat oligonucleotides [(CT)8, (GTG)5, and (GACA)4]. On the basis of the DNA-fingerprints obtained, the Trichoderma aggregate is re-classified into five groups: I (T. reesei, T. todica), II (T. polysporum, T. longibrachiatum, T. koningii, and T. pseudokoningii), III (T. virgatum), IV (T. saturnisporum) and V (T. harzianum). These results contradict the claim that T. reesei is a subspecies of T. longibrachiatum. Furthermore, hybridization with (CA)8 allowed a subdivision of group II, wherein T. pseudokoningii formed a subgroup, IIb, which is highly homologous with, but distinct from subgroup IIa. The results show that RFLP analysis may be used to re-classify the Trichoderma aggregate.
TL;DR: In this paper, the authors proved that the set of feasible points for which MFCQ essentially differs from LICQ is small in a specified sense, and showed that the constraint set (even in semi-infinite optimization) is locally representable in epigraph form.
Abstract: The linear independence constraint qualification (LICQ) and the weaker Mangasarian-Fromovitz constraint qualification (MFCQ) are well-known concepts in nonlinear optimization. A theorem is proved suggesting that the set of feasible points for which MFCQ essentially differs from LICQ is small in a specified sense. As an auxiliary result, it is shown that, under MFCQ, the constraint set (even in semi-infinite optimization) is locally representable in epigraph form.
TL;DR: In this article, a large class of 4D superstring vacua with non-trivial/singular geometries, spacetime supersymmetry and other background fields (axion, dilaton) are found.
Abstract: A large class of new 4-D superstring vacua with non-trivial/singular geometries, spacetime supersymmetry and other background fields (axion, dilaton) are found. Killing symmetries are generic and are associated with non-trivial dilaton and antisymmetric tensor fields. Duality symmetries preserving N=2 superconformal invariance are employed to generate a large class of explicit metrics for non-compact 4-D Calabi-Yau manifolds with Killing symmetries.
TL;DR: It is shown that the matrix of flux control coefficients is an indempotent matrix, which allows an interpretation in terms of the transduction of the effect of parameter perturbations.
Abstract: Various definitions of coefficients in metabolic control analysis are examined with respect to their theoretical consistency and practical applicability. We suggest agreement upon a definition for control coefficients which is clearly distinct from that for response coefficients, in such a way that the former describe inherent properties of the metabolic system while the latter refer to the influence of special parameters. Advantages and drawbacks of using normalized or non-normalized control coefficients are studied. It is shown that normalized control coefficients have the advantage of being invariant to a different rescaling of the particular fluxes. We demonstrate that some problems are easier to tackle if the consistency of time-independent control coefficients with their time-dependent counterparts is taken into account. It is shown that the matrix of flux control coefficients is an indempotent matrix. This allows an interpretation in terms of the transduction of the effect of parameter perturbations. Several aspects of the experimental measurement of control coefficients are discussed, with special reference to the different definitions.
TL;DR: Oligonucleotides hybridizing to simple repetitive DNA patterns are highly informative as probes for DNA fingerprinting in all investigated animal species, including man, and here the applicability of this technique in higher plants is demonstrated.
Abstract: Oligonucleotides hybridizing to simple repetitive DNA patterns are highly informative as probes for DNA fingerprinting in all investigated animal species, including man. Here we demonstrate the applicability of this technique in higher plants. The oligonucleotide probes (GTG)5 and (GATA)4 were used to investigate the differences in DNA fingerprint patterns of the following angiosperm species: Triticum aestivum, Secale cereale, Hordeum vulgare, Beta vulgaris, Petunia hybrida, Brassica oleracea, and Nicotiana tabacum. Two species, Hordeum vulgare as a monocot and Beta vulgaris as a dicot, were analyzed in more detail. Their genomes differ considerably in both amount and organization of the simple repetitive sequences (GATA)n, (GACA)n, (GTG)n, and (CT)n due to the evolutionary distance of these two species. Furthermore, several lines and cultivars of Beta vulgaris and Hordeum vulgare can clearly be distinguished on the basis of their highly polymorphic patterns of these repetitive sequences.
TL;DR: A procedure is described for coupling different discriminators to a new (common) decision rule using the corresponding allocation vectors only, which enables one to cope jointly with data of different structure and/or scales of measurement but without strong restrictions on the number of features.
Abstract: A procedure is described for coupling different discriminators to a new (common) decision rule using the corresponding allocation vectors only. This enables one to cope jointly with data of different structure and/or scales of measurement but without strong restrictions on the number of (especially categorical) features. The method is combined with a consequent cross-validation process securing the results reached. Examples from medical diagnostics demonstrate the usefulness of the proposed procedure, especially in comparison with the known linear discriminant analysis as judged from the error rates obtained.
TL;DR: The vertical Bridgman method is the most favored growth process for CdTe, however, the crystals include a large number of defects as discussed by the authors, which can lead to more monocrystalline material because of the diminishing influence of the end effects.
TL;DR: The assay was used to measure sCD14 in human serum and plasma and other body fluids in health and disease, and in cell culture supernatants, and with the exception of monkeys there was no reactivity with 29 other species screened.
TL;DR: The first three dimensional crystal structure of a seed storage globulin at high resolution is reported, reporting the first protein with this topology possessing no known enzymatic activity from Vicia narbonensis L.
TL;DR: In this paper, the physicico-chemical characteristics and possible formation mechanisms of negative air ions were considered, and it was found that the products of oxygen and nitrogen negative ionization reduce ferricytochromec and nitroblue tetrazolium.
Abstract: The physico-chemical characteristics and possible formation mechanisms of negative air ions are considered. It was found that the products of oxygen and nitrogen negative ionization reduce ferricytochromec and nitroblue tetrazolium, and that these reactions were inhibited by superoxide dismutase. The interaction of negatively ionized oxygen with water led to hydrogen peroxide accumulation, which was inhibited by tetranitromethane or catalase. Nitrogen ionization under these conditions caused the formation of the hydrated electron e
aq
—
and the superoxide anion O
2
—
. The data obtained indicate that the biological activity of negative air ions may be dependent on superoxide. The generation of reactive oxygen ions in the gas phase and also at a gas/water interface is described. A scheme for superoxide production under oxygen and nitrogen ionization is proposed.
TL;DR: Electrophysiological data and distribution ofMechanosensitive cells found in the sinus venosus and right atrium of the frog heart led to the conclusion that they are cardiac fibroblasts.
Abstract: Mechanosensitive cells were found in the sinus venosus and right atrium of the frog heart. Their intracellular membrane potentials were studied in spontaneously beating hearts and in artificially stretched preparations. Membrane resistance was indirectly proportional to the stretch applied. The electrophysiological data and distribution of these cells in the heart led to the conclusion that they are cardiac fibroblasts.
TL;DR: In this paper, the effects of pulsed (or modulated) electromagnetic fields (PEMF) on biological systems are considered. But the effects are not as a result of the influence of foreign energy (as in the case of ionizing radiations), but as a modification of the proper electric in-vivo structure of the biological system.
TL;DR: The data show that activation of α2-adrenergic and opioid receptors causes an inhibition of dihydropyridine-sensitive Ca2+ channels in adrenal chromaffm cells, and these inhibitory modulations are mediated by pertussis-toxin-sensitive G-proteins and may represent a mechanism for a negative feedback signal by agents released from the adrenal medulla.
Abstract: Adrenal chromaffin cells secrete catecholamines and opioids. The effects of these agents on whole-cell Ca2+ channel currents were studied, using bovine adrenal chromaffin cells kept in short term culture. Ca2+ channel currents recorded during voltage-clamp pulses from a holding potential of -80 mV to 0 mV were reversibly reduced by 10 microM epinephrine (in the presence of 1 microM propranolol) or 5 microM of the synthetic opioid, d-Ala2-d-Leu5-enkephalin (DADLE) by approximately 35% and 25%, respectively. The inhibitory action of epinephrine was mimicked by clonidine, reduced by yohimbine but not affected by prazosin. The DADLE-induced reduction of the Ca2+ channel current was antagonized by naloxone. The dihydropyridine (+)PN 200-110 (5 microM) reduced the Ca2+ channel current by approximately 40%; the Ca2+ channel current inhibited by (+)PN 200-110 was not further reduced by epinephrine. Intracellular infusion of guanosine-5'-O-(2-thiodiphosphate) and pretreatment of cells with pertussis toxin abolished the inhibitory effect of both epinephrine and DADLE. In membranes of adrenal chromaffin cells, four pertussis-toxin-sensitive G-proteins were identified, including Gi1, Gi2, Go1 and another Go subtype, possibly Go2. The data show that activation of alpha 2-adrenergic and opioid receptors causes an inhibition of dihydropyridine-sensitive Ca2+ channels in adrenal chromaffin cells. These inhibitory modulations are mediated by pertussis-toxin-sensitive G-proteins and may represent a mechanism for a negative feedback signal by agents released from the adrenal medulla.
TL;DR: Evidence is presented that cis-urocanic acid, generated in vitro by a treatment with UVB light or PUVA, is able to prolong the survival of allogeneic MHC disparate skin grafts in mice, and the rejection of second set grafts was not suppressed.
TL;DR: Although all investigated isolates can clearly and unequivocally be distinguished from each other, aggressive and nonaggressive strains appear as consistent groups with high degrees of similarity.
TL;DR: The results are discussed in relation to biosynthesis of tetrapyrrols in higher plants, regulation of chlorophyll biosynthesis and the action of a plastidderived signal involved in the expression of certain nuclear genes.
Abstract: Components of chlorophyll biosynthesis were investigated in the plastid-ribosome-deficient albostrians mutant of barley (Hordeum vulgare L.). Compared with green leaves, white leaves lacked chloroplast tRNAGlu and 16S ribosomal RNA, but contained a much higher level of the mRNA for glutamate 1-semialdehyde aminotransferase. Substantial amounts of protochlorophyllide were accumulated when the mutant was incubated in a solution of δ-aminolevulinic acid. The level of protochlorophyllide oxidoreductase mRNA (PCOR, EC 1.6.99.1.) in etiolated albostrians plants reached only about 50% of the level in wild-type plants. In addition the content of PCOR protein and the activity of chlorophyll synthetase were distinctly lower than in the wild-type. Mutant and wild-type barley seedlings which were grown under a daily light/dark regime and were therefore nonetiolated both possessed PCOR mRNA. The data presented may help explain the albino phenotype of this mutant. The results are discussed in relation to biosynthesis of tetrapyrrols in higher plants, regulation of chlorophyll biosynthesis and the action of a plastidderived signal involved in the expression of certain nuclear genes.