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C Löffler

Publications and source records attributed to C Löffler.

At least 19 recordsLinked to original sources
PubMed2001

Alagille syndrome associated with a paracentric inversion 20p12.2p13 disrupting the JAG1 gene.

Mutations in the human gene Jagged1 (JAG1) localized in 20p12 have been recently identified as causal for the anomalies found in patients with Alagille syndrome (AGS). This gene encodes a ligand for the Notch1 transmembrane receptor, which plays a key role in cell-to-cell signaling during differentiation and is conserved from C. elegans to human. We report a paracentric inversion (PAI) of chromosome 20p12.2p13 in an individual with AGS who also had alpha-1-antitrypsin deficiency. To our knowledge, this is the first published case of PAI involving the short arm of chromosome 20. Using FISH, fiberFISH, and molecular studies with a approximately 40 kb cosmid clone encompassing the entire 36 kb JAG1 gene, we demonstrate that the gene was disrupted by the inversion breakpoint between exons 5 and 6. An unusual association between two most common causes of chronic liver disease in childhood, AGS and alpha-1-antitrypsin deficiency, as well as their influence on the proband's abnormal phenotype are discussed.

Alagille Syndrome↗
PubMed2001

Which bioengineering assay is appropriate for irritant patch testing with sodium lauryl sulfate?

For testing with sodium lauryl sulphate (SLS), measurements of transepidermal water loss (TEWL) and cutaneous blood flow with laser Doppler (LD) are considered to be the most reliable methods. The aim of this study was to determine which method of measurement should be preferred when conducting SLS testing under varying conditions. Patch testing with SLS at different concentrations and exposure times was performed. TEWL values were compared with those of LD. TEWL values showed distinct changes at low SLS concentrations and short application periods. By contrast, higher SLS concentrations were necessary to increase LD values. Short application of patches changed TEWL rather than LD values. When evaluating SLS patch testing by bioengineering methods, TEWL measurement appears to be more suitable for a test procedure that provokes mild skin reactions (SLS concentration <1%), whereas LD measurement is more appropriate to evaluate pronounced skin reactions (SLS concentration >or=1%).

Dermatitis, Irritant↗
PubMed2001

Irritant patch testing with sodium lauryl sulphate: interrelation between concentration and exposure time.

BACKGROUND: It is well known that the degree of skin reaction to an irritant depends on its concentration and exposure time. OBJECTIVES: To determine the interrelationship between the concentration of sodium lauryl sulphate (SLS) and exposure time in both weak (subclinical) and severe reactions. METHODS: Patch testing with SLS was performed at different concentrations (0.125%, 0.25%, 0.5%, 1.0% and 2.0%) and with different exposure times (3, 6, 12, 24 and 48 h). Evaluation was conducted by measurement of transepidermal water loss and by laser-Doppler flowmetry both 30 min and 24 h after patch removal. RESULTS: We found more reliable and constant skin reactions 24 h after patch removal, and a higher correlation between SLS concentration and skin reaction. CONCLUSIONS: We conclude that the concentration of SLS influences the test outcome to a larger degree than the exposure time. We present formulae by which the outcome of SLS patch testing at various SLS concentrations ranging from 0.125% to 2% and any exposure time between 3 and 24 h can be estimated.

Adolescent↗
PubMed2000

Shift of aberrant antigen expression at relapse or at treatment failure in acute leukemia.

The flow cytometric detection of aberrant antigen expression is one method proposed for the quantification of minimal residual disease (MRD) in acute leukemias. The present study was designed to investigate the stability of the aberrant antigen expression at relapse or at treatment failure of initial chemotherapy. For this purpose, multiparameter immunophenotyping with a panel of 15 monoclonal antibodies was used at diagnosis as well as at relapse (43 patients with overall 65 aberrations) and at treatment failure (35 patients with overall 66 aberrations). There was a significant decrease in the percentage of the initially described aberrant antigen expression on leukemia blasts at relapse (P = 0.001; n = 65) as well as at treatment failure (P = 0.0001; n = 66) considering all aberrations in the whole leukemia population. Concerning only patients with acute myelogenous leukemia (AML), significant decreases in the aberrant expression could be detected at relapse (P = 0.031; n = 42) and at treatment failure (P = 0.0001; n = 52). The changes in patients with acute lymphoblastic leukemia (ALL) were significant only at relapse (P = 0.006; n = 23). Initially, the most informative aberration was not detectable in four patients at relapse and in seven patients at treatment failure. A decrease of under 50% of the initial value was observed in another 8 patients at relapse and in 10 patients at treatment failure. In further studies assessing the detection of aberrant antigen expression for MRD, quantification of the relapses should be explicitly analyzed regarding the persistence of the initially described aberrant antigen expression.

Adult↗
PubMed1997

Sulphonylurea binding in rat isolated glomeruli: pharmacological characterization and dependence on cell metabolism and cytoskeleton.

The kidney is endowed with ATP-sensitive K+ channels (KATP channels) both at the vascular and at the epithelial level. In this study we have characterized the binding of the sulphonylurea glibenclamide, the most widely used blocker of KATP channels, in rat isolated glomeruli. In metabolically intact glomeruli, 3H-glibenclamide labelled two different binding components with affinities of 47 +/- 12 nM and 10 +/- 1 microM and estimated binding capacities of 1.2 +/- 0.1 and 501 +/- 11 pmol/mg protein, respectively. 3H-glibenclamide binding was inhibited differentially by other sulphonylureas (tolbutamide, glibornuride, gliquidone and glipizide) and benzoic acid analogues such as meglitinide, AZ-DF 265 and UL-DF 9. Sulphonylureas interacted with the high affinity component and, in some cases, also with the low affinity component whereas the benzoic acid derivatives inhibited exclusively low affinity glibenclamide binding. Severe metabolic stress affected both components of glibenclamide binding by shifting high affinity binding to the right and reducing the capacity of the low affinity component. Disruption of the cytoskeletal actin filaments by cytochalasin B and D mimicked the effect of metabolic stress on the high affinity component but left the low affinity component unchanged. In crude membranes, the affinity of the first component was again reduced and a major loss of the low affinity sites was observed. The data show that the two binding components of glibenclamide binding in rat isolated glomeruli have very different properties. The high affinity component is not recognized by the benzoic acid derivatives; its affinity is modulated by cell metabolism and the actin component of the cytoskeleton. The low affinity sites are, in their majority, cytosolic. The function and cellular localization of the high affinity sites are under further study.

Adenosine Triphosphate↗
PubMed1997

Activators of protein kinase A induce a glibenclamide-sensitive 86Rb+ efflux in rat isolated aorta.

The effect of activators of protein kinase A on membrane K+ permeability and the interaction of these compounds with cromakalim, an opener of ATP-sensitive K+ channels (K(ATP) channels), were investigated. Membrane K+ permeability was assessed by measuring 86Rb+ efflux from rings of rat aorta. Forskolin, an activator of adenylate cyclase, and isobutylmethylxanthine (IBMX), a nonselective phosphodiesterase inhibitor, induced small, concentration-dependent increases in tracer efflux up to 20-40% over the basal level. The effect of forskolin was abolished by the K+ channel blocker tedisamil (1 microM) and partially inhibited by glibenclamide (1 microM), a relatively selective blocker of K(ATP) channels. Further studies were conducted in the presence of 35 mM KCI in the bath in order to increase the size of the 86Rb+ efflux stimulated by forskolin and IBMX. At high concentrations, these compounds produced a biphasic effect with a peak increase being followed by a lower plateau value. Glibenclamide inhibited the 86Rb+ efflux response to forskolin and IBMX by 50-80%. The K+ channel blockers tedisamil (1 microM), Ba2+ (1 mM) and tetraethylammonium (10 mM) also reduced the peak response to forskolin by about 50% and abolished or greatly inhibited the plateau response. In addition to the small effect on basal 86Rb+ efflux, forskolin (0.3 microM) increased cromakalim-induced 86Rb+ efflux 3.4 times. At higher concentrations, however, a concentration-dependent inhibition was observed with an IC50 value of 7.6 +/- 0.4 microM. 1,9-dideoxyforskolin, which does not increase cAMP, increased neither basal nor cromakalim-induced 86Rb+ efflux; however, it inhibited cromakalim-stimulated tracer efflux with an IC50 value of 22 +/- 2 microM. It is concluded that forskolin and IBMX, probably by increasing intracellular cAMP levels, induce a 86Rb+ efflux from rat aorta, the major part of which is glibenclamide-sensitive and may pass through K(ATP) channels. In addition, low concentrations of forskolin greatly facilitate the K(ATP) channel opening effect of cromakalim whereas high concentrations block the channel; this blocking effect of forskolin is unrelated to the cAMP elevating action.

Animals↗
PubMed1997

Inhibition by protein kinase C of the 86Rb+ efflux and vasorelaxation induced by P1075, a K(ATP) channel opener, in rat isolated aorta.

In rat aortic rings, P1075, an opener of ATP-dependent potassium channels (K(ATP) channels), produces relaxation and 86Rb+ efflux from preloaded tissues; the increase in 86Rb+ efflux qualitatively reflects K(ATP) channel opening. In this study we have investigated the effects of protein kinase C modulation on the 86Rb+ efflux stimulating, the vasorelaxant and the binding properties of P1075. Phorbol 12,13-dibutyrate (PDBu), a direct activator of protein kinase C, inhibited the 86Rb+ efflux produced by P1075 with an IC50 value of 20+/-2 nM. Phorbol 12-myristate 13-acetate (PMA), another stimulator of protein kinase C, was 150 times weaker in this respect whereas 4alpha-PDBu, the inactive stereoisomer of PDBu, was ineffective. Staurosporine (300 nM), an inhibitor of protein kinase C, induced a small but significant increase of P1075-induced tracer efflux and partially reversed the inhibitory effect of PDBu on P1075-stimulated tracer efflux. The vasorelaxant effect of P1075 was inhibited only to a moderate degree by PDBu at concentrations which inhibited P1075-induced 86Rb+ efflux to >90%; however, in the presence of PDBu, the relaxation kinetics of P1075 were increasingly slowed. The vasorelaxant effect of P1075 in the presence of PDBu was still sensitive to inhibition by glibenclamide (100 nM), the standard inhibitor of the K(ATP) channel openers. Specific binding of [3H]-P1075 to rat aortic rings was unaffected by PDBu and PMA even in the micromolar concentration range. The data show that stimulation of protein kinase C inhibits the K+ channel opening effect of P1075 in rat aorta and suggest that protein kinase C may exert a weak tonic inhibition on the K(ATP) channels in this vessel under quasiphysiological conditions. At concentrations of PDBu which essentially abolished P1075-induced tracer efflux, the glibenclamide-sensitive vasorelaxant effect of P1075 was slowed down but not prevented; this supports earlier suggestions that K+ channel openers are also able to relax smooth muscle cells by a mechanism independent of K(ATP) channel opening.

Adenosine Triphosphate↗
PubMed1997

Interaction between thiol-modifying agents and P1075, a K(ATP) channel opener, in rat isolated aorta.

In vascular smooth muscle, openers of ATP-dependent potassium channels (K(ATP) channels), such as P1075 (N-cyano-N'-(1,1-dimethylpropyl)-N"-3-pyridylguanidine), produce relaxation. In this study we have investigated the effects of thiol-modifying agents on the binding of P1075 and on the 86Rb+ efflux stimulating and vasorelaxant effects of the opener in rat aortic rings. The increase in 86Rb+ efflux induced by P1075 was taken as a qualitative measure of K+ channel opening. The hydrophilic SH-group-oxidizing substance, thimerosal (1 to 100 microM), abolished specific binding of [3H]-P1075 with an IC50 value of 7.6+/-1.2 microM; at 30 microM, the half time for inhibition was 38 min. Two other thioloxidizing agents, PMB (4-hydroxy-mercuribenzoic acid) and DTBNP (2,2'-dithio-bis(5-nitropyridine)), inhibited binding up to 86% and 44%, respectively. The disulphide bond reducing substance, DTT (1,4-dithiothreitol, 0.1 to 1 mM), reduced [3H]-P1075 binding by up to 20% and partially reversed the inhibitory effect of thimerosal. In 86Rb+ efflux experiments, thimerosal (3 to 100 microM) concentration-dependently increased basal efflux but inhibited P1075-stimulated tracer efflux with an IC50 value of 7+/-1 microM. The inhibitory effect occurred with a half-time of approximately 8 min and was essentially reversed by DTT. In rings precontracted with noradrenaline, thimerosal inhibited the vasorelaxant effect in a noncompetitive manner, shifting the concentration-relaxation curves to the right and reducing maximum relaxation. The data show that oxidation of thiol groups interferes with the binding of the K(ATP) channel opener, P1075; concomitantly, the 86Rb+ efflux stimulating and the vasorelaxant effects are inhibited. Reduction of disulphide bonds by DTT has only minor effects on the action of P1075. Collectively, the results suggest that intact thiol groups are essential for the functioning of the K(ATP) channel in rat aorta. The different kinetics governing the inhibition of opener binding and of opener-stimulated 86Rb+ efflux suggest that the SH-groups involved in the two processes differ in their accessibility to thimerosal and/or in their reactivity.

Animals↗
PubMed1997

Pharmacological characterization of the sulphonylurea receptor in rat isolated aorta.

1. The binding of the sulphonylurea [3H]-glibenclamide, a blocker of adenosine 5'-triphosphate (ATP)-sensitive K+ channels (KATP channels), was studied in endothelium-denuded rings from rat aorta. 2. [3H]-glibenclamide labelled two classes of binding sites with KD values of 20 +/- 5 nM and 32 +/- 1 microM. The high affinity component, which comprised 17% of total binding at 1 nM [3H]-glibenclamide, had an estimated binding capacity of 150 fmol mg-1 wet weight. 3. Other sulphonylureas such as glipizide and glibornuride and the sulphonylurea-related carboxylate, AZ-DF 265, inhibited high affinity [3H]-glibenclamide binding with the potencies expected from their K+ channel activity. At very high concentrations, AZ-DF 265 and glipizide started to interact also with the low affinity component of [3H]-glibenclamide binding. 4. Openers of the ATP-sensitive K+ channel belonging to different structural groups inhibited only the high affinity [3H]-glibenclamide binding; the potencies in this assay were similar to those obtained in functional (i.e. vasorelaxation) studies. 5. High affinity [3H]-glibenclamide binding was abolished by prolonged hypoxia combined with metabolic inhibition. 6. The data indicate that the high affinity component of [3H]-glibenclamide binding mediates the block of the KATP channel by the sulphonylureas in rat aorta; hence, it represents the sulphonylurea receptor in this vessel. The pharmacological properties of this binding site resemble those of the binding site for the openers of the KATP channel; present evidence suggests that these two classes of sites are negatively allosterically coupled.

Adenosine Triphosphate↗
PubMed1996

Interstitial deletion 5p accompanied by dicentric ring formation of the deleted segment resulting in trisomy 5p13-cen.

Karyotypes with an interstitial deletion and a marker chromosome formed from the deleted segment are rare. We identified such a rearrangement in a newborn infant, who presented with macrocephaly, asymmetric square skull, minor facial anomalies, omphalocele, inguinal hernias, hypospadias, and club feet. The karyotype 46,XY,del(5) (pter --> p13::cen --> qter)/47,XY,+dicr(5)(:p13 --> cen::p13 --> cen), del(5)(pter --> p13::cen --> qter) was identified by banding studies and FISH analysis in the peripheral lymphocytes. One breakpoint on the del(5) maps distal to GDNF, and FISH analysis using an alpha-satellite probe suggests that the proximal breakpoint maps within the centromere. The dicentric r(5) consists of two copies of the segment deleted in the del(5), resulting in trisomy of proximal 5p (5p13-cen). The phenotype of the propositus is compared with other trisomy 5p cases and possible mechanisms for the generation of this unique chromosomal rearrangement are discussed.

Abnormalities, Multiple↗
PubMed1994

Molecular structure and chromosomal mapping of the human homolog of the agouti gene.

The agouti (a) locus in mouse chromosome 2 normally regulates coat color pigmentation. The mouse agouti gene was recently cloned and shown to encode a distinctive 131-amino acid protein with a consensus signal peptide. Here we describe the cloning of the human homolog of the mouse agouti gene using an interspecies DNA-hybridization approach. Sequence analysis revealed that the coding region of the human agouti gene is 85% identical to the mouse gene and has the potential to encode a protein of 132 amino acids with a consensus signal peptide. Chromosomal assignment using somatic-cell-hybrid mapping panels and fluorescence in situ hybridization demonstrated that the human agouti gene maps to chromosome band 20q11.2. This result revealed that the human agouti gene is closely linked to several traits, including a locus called MODY (for maturity onset diabetes of the young) and another region that is associated with the development of myeloid leukemia. Initial expression studies with RNA from several adult human tissues showed that the human agouti gene is expressed in adipose tissue and testis.

Agouti Signaling Protein↗
PubMed1994

The gene for the amyloid precursor-like protein APLP2 is assigned to human chromosome 11q23-q25.

The human amyloid precursor-like protein APLP2 is a highly conserved homologue of a sequence-specific DNA-binding mouse protein with a predicted function in the cell cycle. Somatic cell hybrids segregating human chromosomes were used to assign the APLP2 gene to chromosome 11. Fluorescence in situ hybridization confirmed this assignment and further localized the gene to q23-q25.

Amyloid beta-Protein Precursor↗
PubMed1994

Interstitial deletion of 22q11 in DiGeorge syndrome detected by high resolution and molecular analysis.

Two patients with DiGeorge syndrome (DGS), one with and one without characteristic dysmorphic facial features, were studied by high resolution banding, fluorescence in situ hybridization (FISH) and quantitative Southern blotting. In both patients, even in the one with no typical facial stigmata, a microdeletion within 22q11.2 was detected. FISH analysis, in particular, is most useful in screening for 22q11.2 segmental monosomy in patients with DGS and DGS-related features.

Blotting, Southern↗
PubMed1992

Gene structure of semenogelin I and II. The predominant proteins in human semen are encoded by two homologous genes on chromosome 20.

The genes for semenogelin I and II, the major protein constituents of the human seminal fluid, have been characterized by three overlapping clones in bacteriophage lambda, encompassing 31.5 kilobases (kb) of genomic DNA. The two genes are located 11.5 kb apart in the region q12-q13.1 on chromosome 20. Both genes are relatively compact, spanning only 2.7 and 3.1 kb, respectively. The transcription units are composed of three exons, of which the first encodes the signal peptide, the second encodes the secreted protein, while the third solely contains 3'-noncoding nucleotides. The nucleotide sequences exhibit a similarity of close to 90% in the exons and exceeding 80% in the introns and flanking nucleotides.

Amino Acid Sequence↗
PubMed1992

The gene for bone morphogenetic protein 2A (BMP2A) is localized to human chromosome 20p12 by radioactive and nonradioactive in situ hybridization.

Bone morphogenetic protein 2A (BMP2A), a member of the decapentaplegic-Vg-related family, belongs to the transforming growth factor beta superfamily and has a striking sequence similarity to the decapentaplegic locus in Drosophila melanogaster, a major determinant of pattern specification during embryogenesis. BMP2A is thought to be involved in cartilage and bone formation during embryogenesis, but may have additional functions in morphogenesis as implied by its expression in various organs and embryonic tissues of mice. Human BMP2A, assigned to chromosome 20 by the use of human-Chinese hamster ovary cell hybrids, is considered to be a reasonable candidate gene for the autosomal dominant disease of fibrodysplasia (myositis) ossificans progressiva. We have confirmed the localization of BMP2A to chromosome 20 and regionally assigned the locus to 20p12 by radioactive and nonradioactive in situ hybridization.

Bone Morphogenetic Proteins↗
PubMed1992

The human gene for oxytocin-neurophysin I (OXT) is physically mapped to chromosome 20p13 by in situ hybridization.

Two posterior pituitary hormones oxytocin and arginine-vasopressin control the important activities of water excretion, parturition and lactation. Both these hormones are synthesized as inactive precursors in the hypothalamus along with their carrier proteins neurophysin I and neurophysin II respectively and are activated upon transport to posterior pituitary. Human genes for both oxytocin-neurophysin I (OXT) and arginine-vasopressin-neurophysin II (ARVP) are cloned and found to be linked on chromosome 20 separated by approximately 12 kb of intergenic sequences. Though OXT is not yet associated with any disease, ARVP is linked to the autosomal dominant disease neurohypophyseal diabetes insipidus (AD-NDI). We have mapped regionally the OXT locus to chromosome 20p13 by both radioactive (ISH) and fluorescence in situ hybridization (FISH).

Arginine Vasopressin↗