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91.
Holger Michael Hans-Christian Fecke Oliver Fleck Herbert Gutz 《Molecular genetics and genomics : MGG》1995,249(3):297-300
Mating-type (MT) switching in homothallic (h> 90 ) strains of Schizosaccharomyces pombe is initiated by a DNA double-strand break (DSB) at the distal end of the expression cassette mat1. The cis-acting smt-s1 mutation C13-P11 reduces the frequency of MT switching. It is a small deletion mapping approximately 50 by distal to the site of the DSB. From the h 90 smt-s1 strain we isolated 13 mutants with a hyperspeckled iodine reaction. In these mutants the frequency of MT switching is increased. The mutations define nine different hsp genes, none of which maps in or close to the MT region. We tested one mutant of each gene for the presence of DSBs at mat1. Curiously, in none of the h 90 smt-s1 hsp strains could DSBs be detected, although some sporulate nearly as efficiently as the h 90 smt-n wild type. The hsp mutations show no effect in smt-0 strains; the smt-0 deletion abolishes MT switching completely. Furthermore, we tested the interaction of hsp1-1 with swi1, swi2 and swi7 mutations. hsp1-1 has no effect in swi2 strains, whereas it increases MT switching in swi7 and, to a lesser degree, in swi1 mutants. 相似文献
92.
Hans-Christian Siebert Sabine Andre Gerd Reuter Robert Kaptein Johannes F.G. Vliegenthart Hans-Joachim Gabius 《Glycoconjugate journal》1997,14(8):945-949
The human pentraxin serum amyloid P component (SAP) exhibits no microheterogeneity in its complex di-antennary glycan. To
elucidate whether the removal of sialic acids from this glycoprotein might affect the accessibility of certain amino acid
residues of the protein we employed the laser photo CIDNP approach as a sensitive tool. The CIDNP effect is generated by the
interaction of a photoexcited dye with reactive amino acids and results in enhanced absorption- or emission-signals which
can be observed for the three aromatic amino acids histidine, tryptophan, and tyrosine if they are accessible to the dye.
Therefore, this technique can be applied to explore surface exposure of these amino acid residues. The respective spectra
of SAP and enzymatically desialylated SAP were determined. Six tryptophan/histidine signals and one tyrosine signal are present
in the aromatic part of the CIDNP difference spectrum of SAP. The corresponding spectrum of desialylated SAP shows remarkable
alterations. The chemical shift of one Trp/His-characteristic signal is decreased by 0.1 ppm. One Trp/His-signal disappeared
and a new one was formed in the CIDNP difference spectrum of desialylated SAP, while the other signals were unaffected. The
Tyr signal has a clearly enhanced intensity in desialylated SAP. Therefore, the removal of sialic acid moieties from the single
N-glycan of each monomer apparently affects surface presentation of distinct CIDNP-reactive amino acids of SAP [1]. A conformational
change of the protein part of SAP in relation with a different orientation of the desialylated oligosaccharide chain in comparison
to the complete one is a possible explanation of our CIDNP results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
93.
Saskia Schadow Hans-Christian Siebert Günter Lochnit Jens Kordelle Markus Rickert Jürgen Steinmeyer 《PloS one》2013,8(1)
Destruction of articular cartilage is a characteristic feature of osteoarthritis (OA). Collagen hydrolysates are mixtures of collagen peptides and have gained huge public attention as nutriceuticals used for prophylaxis of OA. Here, we evaluated for the first time whether different bovine collagen hydrolysate preparations indeed modulate the metabolism of collagen and proteoglycans from human OA cartilage explants and determined the chemical composition of oligopeptides representing collagen fragments. Using biophysical techniques, like MALDI-TOF-MS, AFM, and NMR, the molecular weight distribution and aggregation behavior of collagen hydrolysates from bovine origin (CH-Alpha®, Peptan™ B 5000, Peptan™ B 2000) were determined. To investigate the metabolism of human femoral OA cartilage, explants were obtained during knee replacement surgery. Collagen synthesis of explants as modulated by 0–10 mg/ml collagen hydrolysates was determined using a novel dual radiolabeling procedure. Proteoglycans, NO, PGE2, MMP-1, -3, -13, TIMP-1, collagen type II, and cell viability were determined in explant cultures. Groups of data were analyzed using ANOVA and the Friedman test (n = 5–12). The significance was set to p≤0.05. We found that collagen hydrolysates obtained from different sources varied with respect to the width of molecular weight distribution, average molecular weight, and aggregation behavior. None of the collagen hydrolysates tested stimulated the biosynthesis of collagen. Peptan™ B 5000 elevated NO and PGE2 levels significantly but had no effect on collagen or proteoglycan loss. All collagen hydrolysates tested proved not to be cytotoxic. Together, our data demonstrate for the first time that various collagen hydrolysates differ with respect to their chemical composition of collagen fragments as well as by their pharmacological efficacy on human chondrocytes. Our study underscores the importance that each collagen hydrolysate preparation should first demonstrate its pharmacological potential both in vitro and in vivo before being used for both regenerative medicine and prophylaxis of OA. 相似文献
94.
Grånäs C Lundholt BK Loechel F Pedersen HC Bjørn SP Linde V Krogh-Jensen C Nielsen EM Praestegaard M Nielsen SJ 《Journal of biomolecular screening》2006,11(4):423-434
The RAS-mitogen-activated protein kinase (MAPK) signaling pathway has a central role in regulating the proliferation and survival of both normal and tumor cells. This pathway has been 1 focus area for the development of anticancer drugs, resulting in several compounds, primarily kinase inhibitors, in clinical testing. The authors have undertaken a cell-based, high-throughput screen using a novel ERF1 Redistribution assay to identify compounds that modulate the signaling pathway. The hit compounds were subsequently tested for activity in a functional cell proliferation assay designed to selectively detect compounds inhibiting the proliferation of MAPK pathway-dependent cancer cells. The authors report the identification of 2 cell membrane-permeable compounds that exhibit activity in the ERF1 Redistribution assay and selectively inhibit proliferation of MAPK pathway-dependent malignant melanoma cells at similar potencies (IC(50)=< 5 microM). These compounds have drug-like structures and are negative in RAF, MEK, and ERK in vitro kinase assays. Drugs belonging to these compound classes may prove useful for treating cancers caused by excessive MAPK pathway signaling. The results also show that cell-based, high-content Redistribution screens can detect compounds with different modes of action and reveal novel targets in a pathway known to be disease relevant. 相似文献
95.
We recently described the identification of a centrosome/spindle pole associated protein, CSPP, involved in cell cycle progression. Here we report a CSPP isoform denoted CSPP-L, with a 294 amino acids longer N-terminus and a 51 amino acids insertion located in the coiled-coil mid-domain. Expression analysis indicates an inverse cell cycle dependent regulation. CSPP mRNA expression is highest in G1 whereas CSPP-L expression is highest in G2/M. Ectopic expression of CSPP-L impairs cell cycle progression weaker in G1 than CSPP. Furthermore, normal mitotic phenotypes were observed in CSPP-L but not in CSPP transfectants. CSPP-L relocates from spindle microtubules and poles in metaphase to the mid-spindle in anaphase and concentrates at the mid-body in telophase/cytokinesis. CSPP-L high-expressing mitotic cells were predominantly characterized by lagging chromosomes or monopolar spindles, in contrast to the predominant multipolar spindles observed with CSPP expression. The different effects of CSPP and CSPP-L on microtubule organization in mitosis depend on the coiled-coil mid-domain insertion. The common C-terminal domain is required to repress that activity until mitosis. Notably, this C-terminal domain alone can associate with centrosomes in a microtubule independent manner. Taken together, CSPP and CSPP-L interact with centrosomes and microtubules and can differently affect microtubule organization. 相似文献
96.
Kornau HC 《Cell and tissue research》2006,326(2):517-533
GABAB receptors modulate transmitter release and postsynaptic membrane potential at various types of central synapses. They function as heterodimers of two related seven-transmembrane domain receptor subunits. Trafficking, activation and signalling of GABAB receptors are regulated both by allosteric interactions between the subunits and by the binding of additional proteins. Recent studies have shed light on the roles of GABAB receptors in plasticity processes at excitatory synapses. This review summarizes our knowledge of the localization, structure and function of GABAB receptors in the central nervous system and their use as drug targets for neurological and psychiatric disorders. 相似文献
97.
Hans-Christian Siebert Robert Kaptein Jaap J Beintema Ukun M Soedjanaatmadja Christine S Wright Ann Rice Reinhard G Kleineidam Susanne Kruse Roland Schauer Petra J.W Pouwels Johannis P Kamerling Hans-Joachim Gabius Johannes F.G Vliegenthart 《Glycoconjugate journal》1997,14(4):531-534
The side chains of tyrosine, tryptophan and histidine are able to produce CIDNP (Chemically Induced Dynamic Nuclear Polarization)
signals after laser irradiation in the presence of a suitable radical pair-generating dye. Elicitation of such a response
in proteins implies surface accessibility of the respective groups to the light-absorbing dye. In principle, this technique
allows the monitoring of the effect of ligand binding to a receptor and of site-directed mutagenesis on conformational aspects
of any protein if CIDNP-reactive amino acids are involved. The application of this method in glycosciences can provide insights
into the protein-carbohydrate interaction process, as illustrated in this initial model study for several N-acetyl-glucosamine-binding
lectins of increasing structural complexity as well as for a wild type bacterial sialidase and its mutants. Experimentally,
the shape and intensity of CIDNP signals are determined in the absence and in the presence of specific glycoligands. When
the carbohydrate is bound, CIDNP signals of side chain protons of tyrosine, tryptophan or histidine residues can be broadened
and of reduced intensity. This is the case for hevein, pseudo-hevein, the four hevein domains-containing lectin wheat germ
agglutinin (WGA) and the cloned B-domain of WGA 1 (domB) representing one hevein domain. This response indicates either a
spatial protection by the ligand or a ligand-induced positioning of formerly surface-exposed side chains into the protein’s
interior part, thereby precluding interaction with the photo-activated dye. Some signals of protons from the reactive side
chains can even disappear when the lectin-ligand complexes are monitored. The ligand binding, however, can apparently also
induce a conformational change in a related lectin that causes the appearance of a new signal, as seen for Urtica dioica agglutinin
(UDA) which consists of two hevein domains. Additionally, the three CIDNP-reactive amino acids are used as sensors for the
detection of conformational changes caused by pH variations or by deliberate amino acid exchanges, as determined for the isolectins
hevein and pseudo-hevein as well as for the cloned small sialidase of Clostridium perfringens and two of its mutants. Therefore,
CIDNP has proven to be an excellent tool for protein-carbohydrate binding studies and can be established in glycosciences
as a third biophysical method beside X-ray-crystallography and high-resolution multidimensional NMR studies which provides
reliable information of certain structural aspects of carbohydrate-binding proteins in solution.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
98.
Juergen Braun Johannes Bernarding Hans-Christian Koennecke Karl-Juergen Wolf Thomas Tolxdorff 《Computer methods in biomechanics and biomedical engineering》2013,16(6):411-420
Diffusion-weighted imaging enables the diagnosis of cerebral ischemias very early, thus supporting therapies such as thrombolysis. However, morphology and tissue-characterizing parameters (e.g. relaxation times or water diffusion) may vary strongly in ischemic regions, indicating different underlying pathologic processes. As the determination of the parameters by a supervised segmentation is very time consuming, we evaluated whether different infarct patterns may be segmented by an automated, multidimensional feature-based method using a unified segmentation procedure. Ischemias were classified into 5 characteristic patterns. For each class, a 3D histogram based on T 2 - and diffusion-weighted images as well as calculated apparent diffusion coefficients (ADC) was generated from a representative data set. Healthy and pathologic tissue classes were segmented in the histogram as separate, local density maxima with freely shaped borders. Segmentation control parameters were optimized in a 3-step procedure. The method was evaluated using synthetic images as well as results of a supervised segmentation. For the analysis of cerebral ischemias, the optimal control parameter set led to sensitivities and specificities between 1.0 and 0.9. 相似文献
99.
Wang S Villablanca EJ De Calisto J Gomes DC Nguyen DD Mizoguchi E Kagan JC Reinecker HC Hacohen N Nagler C Xavier RJ Rossi-Bergmann B Chen YB Blomhoff R Snapper SB Mora JR 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(1):141-150
Gut-associated dendritic cells (DC) synthesize all-trans retinoic acid, which is required for inducing gut-tropic lymphocytes. Gut-associated DC from MyD88(-/-) mice, which lack most TLR signals, expressed low levels of retinal dehydrogenases (critical enzymes for all-trans retinoic acid biosynthesis) and were significantly impaired in their ability to induce gut-homing T cells. Pretreatment of extraintestinal DC with a TLR1/2 agonist was sufficient to induce retinal dehydrogenases and to confer these DC with the capacity to induce gut-homing lymphocytes via a mechanism dependent on MyD88 and JNK/MAPK. Moreover, gut-associated DC from TLR2(-/-) mice, or from mice in which JNK was pharmacologically blocked, were impaired in their education to imprint gut-homing T cells, which correlated with a decreased induction of gut-tropic T cells in TLR2(-/-) mice upon immunization. Thus, MyD88-dependent TLR2 signals are necessary and sufficient to educate DC with gut-specific imprinting properties and contribute in vivo to the generation of gut-tropic T cells. 相似文献
100.
Anne Kjaergaard Danielsen Cecilie Okholm Hans-Christian Pommergaard Jakob Burcharth Jacob Rosenberg 《PloS one》2014,9(7)