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H Fischer

Publications and source records attributed to H Fischer.

At least 253 records · Page 14Linked to original sources
PubMed1992

Image reconstruction for echo planar imaging with nonequidistant k-space sampling.

Echo planar imaging is characterized by scanning the 2D k-space after a single excitation. Different sampling patterns have been proposed. A technically feasible method uses a sinusoidal readout gradient resulting is measured data that does not sample k-space in an equidistant manner. In order to employ a conventional 2D-FFT image reconstruction, the data have to be converted to a cartesian grid. This can be done either by interpolation or alternatively by a generalized transformation. Filtering methods are described to minimize ghosting artifact that is typical in echo planar imaging. Results both from computer simulation and from experiments will be presented. Experimental images were obtained using a 2-T whole-body research system.

Artifacts↗
PubMed1992

The outwardly rectifying Cl- channel is not involved in cAMP-mediated Cl- secretion in HT-29 cells: evidence for a very-low-conductance Cl- channel.

The patch-clamp technique and transepithelial current measurements in conjunction with analysis of transepithelial current noise were employed in order to clarify the role of the outwardly rectifying, depolarization-induced Cl- channel (ORDIC) during cAMP-mediated Cl- secretion in HT-29/B6 cells. Confluent monolayers growing on permeable supports were used in order to ensure the apical location of measured Cl- channels. The ORDIC needed to be activated by excision and/or depolarization, and was found in both cAMP-stimulated and non-stimulated cells. Both 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) and 4,4'-dinitro-2,2'-stilbenedisulphonate (DNDS) induced fast flickery-type blocks of the ORDIC at low, micromolar blocker concentrations and were used as a probe for ODIC. However, these substances were ineffective in blocking transepithelial forskolin-induced Cl- secretion of monolayers in Ussing chambers. No inhibitory effect at all was detected for DNDS up to 1 mmol/l. NPPB blocked the ORDIC at low concentrations (IC50 = 0.5 +/- 0.3 mumol/l) by reducing its open probability, but NPPB did not block forskolin-induced Cl- secretion unless high concentrations were used (IC50 = 240 +/- 10 mumol/l). In order to exclude effects of NPPB other than on the apical Cl- channel, transepithelial measurements were performed in basolaterally amphotericin-permeabilized, forskolin-stimulated preparations, and a serosal-to-mucosal Cl- gradient was applied as a driving force. Under these conditions, NPPB's inhibitory effects were also very small. Noise analysis of this gradient-driven Cl- current showed a very-low-frequency Lorentzian noise component (fc = 1.4 +/- 0.2 Hz), which was not compatible with Lorentzians predicted from single-channel gating of ORDIC.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1992

Intracellular Ca2+ signalling is modulated by K+ channel blockers in colonic epithelial cells (HT-29/B6).

We investigated the inhibitory action of K+ channel blockers on carbachol-stimulated Ca2+ entry into human Cl(-)-secretory colonic epithelial cells (HT-29/B6). Digital imaging of the fluorescent calcium indicator dye fura-2 was performed to monitor effects of K+ channel blockers on cytosolic calcium in resting and carbachol-stimulated HT-29/B6 cells. Stimulation with the muscarinic agonist carbachol (100 microM) caused a clearly biphasic intracellular calcium (Cai) response: Cai was stimulated from resting levels (85 +/- 3 nM, n = 100) to a sudden transient peak (821 +/- 44 nM) followed by a sustained plateau (317 +/- 12 nM). The maintained elevation was dependent on external Ca2+ and represented a new steady state between Ca2+ entry and exit across the plasma membrane. A monophasic Ca2+ response was induced in the absence of external Ca2+ and after the initial peak Cai returned to baseline. The Cai plateau was reduced to resting levels by either the muscarinic antagonist atropine (1 microM) or the inorganic Ca2+ channel blocker lanthanum (effective concentration for 50% inhibition of Cai plateau EC50 = 68 +/- 18 nM), but it was unaffected by the organic Ca2+ channel blockers verapamil and nifedipine. Barium, lidocaine and 4-nitro- 2-(3-phenylpropylamino)benzoate (NPPB), well-known blockers of basolateral K+ channels of HT-29/B6 cells, rapidly and reversibly reduced carbachol-stimulated Ca2+ entry.(ABSTRACT TRUNCATED AT 250 WORDS)

Atropine↗
PubMed1992

Reversal of gelatin-impaired wound healing in rats by exogenous fibronectin.

Animal experiments have shown that administration of gelatin results in a deprivation of plasma fibronectin (FN) and impaired wound healing. For further elucidation of these findings a therapy study with purified human FN was performed in rats. Fifty animals received a standard burn injury of 1% body surface and were divided into five experimental groups. Positive controls given no further treatment or treated with solvent only served for estimation of normal healing. For a negative control, 10 animals received three intraperitoneal injections of gelatin (58 mg/kg body wt) on Days 0, 1, and 2 after injury. They exhibited a striking lack of plasma FN (Day 1) and a significant delay of wound contraction (Days 7 and 14). In the therapy groups each administration of gelatin was followed by an intraperitoneal or intracardiac injection of FN (58 mg/kg body wt) 1 hr later. In these animals the negative effect of gelatin upon plasma FN and wound contraction was prevented. According to this study wound healing is menaced by FN deficiency and can be optimized by substitution of exogenous FN.

Animals↗
PubMed1992

The LFA-3 adhesion pathway is differently utilized by superantigen-activated human CD4+ T-cell subsets.

The superantigen SEA binds to MHC class II molecules and activates a large fraction of T cells as a result of interaction with particular TCR-V beta sequences. MHC class II transfected CHO cells induce a marginal CD4+ T-cell proliferation in the presence of SEA. CHO cells transfected with both MHC class II and LFA-3 (HLA-DR4/LFA-3 double transfectants) supported a vigorous T-cell proliferation and required 1000-fold lower SEA concentration than DR4-transfected cells. DR4/LFA-3 double transfectants presenting SEA to CD4+ T cells induced large amounts of IFN-gamma, while single DR4 transfectants failed to elicit IFN-gamma production. CD4+45RA+ naive T cells proliferated much more strongly compared with CD4+45R0+ memory T cells when SEA was presented by the DR4/LFA-3-transfected cells. In contrast, IFN-gamma production was only detected in CD4+45R0+ memory cells. The enhanced proliferation by the CD4+45RA+ naive T cells was not due to a stronger binding to the accessory DR4/LFA-3 cells. Human CD4+ T-cell lines mediated a low level of SEA-dependent cell-mediated cytotoxicity (SDCC) against DR4 target cells, whereas a strong SDCC was mediated against DR4/LFA-3-expressing target cells. These results demonstrate that superantigen-activated human CD4+ T cells require the adhesion molecule LFA-3 for optimal stimulation and that the CD4+ naive and memory T-helper cells are different in their response to LFA-3 as an accessory molecule.

Animals↗
PubMed1992

Volume-sensitive basolateral K+ channels in HT-29/B6 cells: block by lidocaine, quinidine, NPPB, and Ba2+.

Volume-sensitive basolateral K+ channels were studied in apically amphotericin B-permeabilized HT-29/B6 monolayers in Ussing chambers with current fluctuation analysis. The basolateral K+ conductance and Lorentzian K+ channel noise were osmotically activated in presence of Cl- concentrations greater than or equal to 74 mM. Under isotonic conditions with 148 mM Cl-, a large transepithelial K+ current of 500 +/- 16.8 microA/cm2 and a spontaneous Lorentzian K+ channel noise with a corner frequency of 29.8 +/- 1.6 Hz (n = 31) were observed. Increasing extracellular osmolalities by addition of sucrose sensitively decreased the K+ current across the basolateral membrane. Half-maximal sucrose concentration was 20 +/- 6 mM for this shrinkage maneuver. The osmotically sensitive K+ pathway was similarly activated with the halide Br- and selective for K+ over Rb+ (4:1). The established K+ channel blockers lidocaine [50% inhibitory concentration (IC50) = 49.0 +/- 3.7 microM], quinidine (IC50 = 10.1 +/- 1.3 microM), and also the chloride channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (IC50 = 114 +/- 2.1 microM) completely inhibited basolateral K+ currents, whereas 46% of K+ current was blocked by barium (IC50 = 95.3 +/- 23.2 microM). Osmotic sensitivity of this K+ conductance made a correction for hypertonic effects of added blockers necessary, and considerable osmotic effects of blockers at commonly used doses were shown. All blockers induced dose dependently additional Lorentzian noise, indicating a direct inhibitory action on basolateral K+ channels. In this human Cl- secretory cell line, volume-sensitive K+ channels are localized only in the basolateral membrane and may modulate osmotic regulation when HT-29 cells swell.

Adenocarcinoma↗
PubMed1992

Fast one-step procedure for the detection of nucleic acids in situ by primer-induced sequence-specific labeling with fluorescein-12-dUTP.

We provide fast, simple, one-step procedures for sequence-specific detection of nucleic acids in situ. Tandem repeat sequences in DNA are stained within 30 min, and mRNA is stained within 2 h. The procedures are based on the incorporation of the newly available fluorescein-labeled dUTP into DNA synthesized in situ by primed in situ labeling, with denatured fragments of cloned DNA or oligonucleotides as primers. The extreme speed and simplicity of the reaction make it attractive for automatization in routine laboratory procedures and opens up new diagnostic possibilities.

DNA↗
PubMed1992

Neurochemical and motor effects of high dose haloperidol treatment: exacerbation by tryptophan supplementation.

The neurochemical and motor effects of a high dose (25 mg/kg) of haloperidol were assessed in male Sprague-Dawley rats. In Experiment 1, this high dose of haloperidol caused dramatic increases in striatal dopaminergic and serotonergic turnover that only returned to control levels 100 hr after injection. In the second experiment, the same dose of haloperidol was administered twice over a 3-week interval in the presence or absence of a dietary tryptophan supplement added to the drinking water. Rats were assessed for disruption of locomotor behavior (using the rotorod) as well as the occurrence of spontaneous (dyskinetic-like) chewing and head twitching. It was observed that haloperidol impaired rotorod performance in a manner that paralleled the time course of the neurochemical changes in Experiment 1. In addition, the tryptophan (consumed at an average of 157 mg/kg/day) exacerbated the deficit in rotorod performance in haloperidol-treated rats after the first, but not after the second, haloperidol injection. Finally, the combination of haloperidol plus tryptophan was found to cause a long-lasting increase in spontaneous chewing movements that lasted 56 days after the first injection. These observations are interpreted in the context of tryptophan supplementation to antipsychotic therapy.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

[Familial Mediterranean fever--a case report].

A case of a ten years old boy with recurrent fever and abdominal pain starting at the age of five years is reported. Later the attacks were accompanied by chest pain. There were only indifferent changes in laboratory examination. Neither a wide range of antibiotics, nor appendectomy and tonsillectomy prevented the boys symptoms. The diagnose was established after five years by a positive Metaraminol test, that precipitated a disease-like attack. The therapeutic use of colchicine-salicylate reduced the severity and frequency of attacks in out patient. In agreement with other authors it should be emphasized, that in general the benefit of colchicine outweighs possible side effects of a long term therapy also in children.

Appendectomy↗
PubMed1992

[Results of therapy of anemia in pregnancy].

Among 106 pregnant women with anaemia a typical state of iron deficiency could be shown at only 36.8%. 22.5% of the patients had a decreased vitamin B12 level without any characteristic symptoms of a megaloblastic anaemia. Predominantly the grade of the anaemia was small. The mean value of hemoglobin lied at 7.1 +/- 0.59 mmol/l. The severity of the anaemia didn't show any connection to the vitamin B12 level or parameters of the iron metabolism. With a combined therapy of iron, folic acid and vitamin B12 an increase of the Hb-level could be noticed at only 44.3% of the patients. The haematological findings, taken before the therapy, as well as the therapy results show that an important part of anaemias in pregnancy is caused by a complex genesis as a result of immunological reactions in pregnancy.

Adolescent↗
PubMed1991

[Changes in the blood and plasma volumes during diagnostic angiocardiography. Differences between high- and low-osmolality contrast media].

Changes in blood and plasma volumes were investigated in the course of diagnostic cardiac catheterizations, comparing the effect of a high and a low osmolar contrast medium in 30 patients (5 women and 25 men; mean age 53 [19-76] years) with coronary heart disease (n = 27) or valvular defect (n = 3). Using a randomized, double-blind protocol 15 patients received amidotrizoic acid (2.1 osmol/kg; mean dosage 166 +/- 68 or 2.2 +/- 1.1 ml/kg), while 15 patients received iopamidol (0.8 osmol/kg; mean dosage 154 +/- 78 ml or 2.1 +/- 1.0 ml/kg). The indocyanine-green method and the haematocrit were used to measure blood and plasma volumes immediately before and after the angiocardiography. Blood volume after amidotrizoic acid injection increased by a mean of 4.9% (228 +/- 242 ml) and by 0.4% (17 +/- 197 ml) after iopamidol (P less than 0.05). Plasma volume increased by a mean of 11.8% (331 +/- 150 ml) after amidotrizoic acid and 5.7% (157 +/- 97 ml) after iopamidol (P less than 0.01). The increase in plasma volume correlated with the dose of contrast medium: 2 ml per ml amidotrizoic acid (r = 0.93) and 1 ml per ml iopamidol (r = 0.82).--During angiocardiography blood and plasma volume may increase by up to 500 ml, an increase which depends not only on dosage but also on the osmolality of the injected contrast medium.

Adult↗
PubMed1991

Induction of interleukin-1 in human monocytes by the superantigen staphylococcal enterotoxin A requires the participation of T cells.

Nanogram quantities of the bacterial superantigen Staphylococcal Enterotoxin A (SEA) induced significant amounts of extracellular IL-1 alpha and IL-1 beta in human peripheral blood mononuclear cells. Induction of maximal IL-1 alpha and IL-1 beta levels by lipopolysaccharide (LPS) required microgram quantities. LPS induced detectable extracellular IL-1 content within 3-6 hr and maximal levels were detected already after 12 hr. Induction of IL-1 production by SEA showed a delayed release with peak values after 24-48 hr. IL-1 beta was the major species of IL-1 seen in both SEA- and LPS-stimulated culture supernatants. SEA was in general a relatively stronger inducer of extracellular IL-1 alpha than LPS. SEA-induced extracellular IL-1 production in human monocytes was entirely dependent on the presence of T cells, whereas addition of T cells to LPS-stimulated purified human monocytes only marginally enhanced the extracellular IL-1 production. The capacity to induce extracellular IL-1 production in monocytes in response to SEA was high in the CD4+ 45RO+ memory T cell subset, whereas CD4+ 45RA+ naive T cells and CD8+ T cells had lower IL-1-inducing capacity. The T cell help for IL-1 production could not be replaced by a panel of T cell-derived recombinant lymphokines added to SEA-stimulated monocytes, including IFN-gamma and TNF, indicating the participation of cell membrane-bound ligands or hitherto unidentified soluble mediators.

Antigens, Bacterial↗
PubMed1991

[Therapy-refractory fulminant meningococcal sepsis].

Two cases of the severe form of meningococcal infection are described. A 17-year-old girl and a (unrelated) 2-year-old boy suddenly developed fever and rigor. Several hours later petechiae of the skin were noted: they rapidly spread. On admission the girl was found to have a severe consumptive coagulopathy (prothrombin 24%, partial thromboplastin time 104 sec, fibrinogen 73 mg/dl, platelets 35,000/microliters). She died two-and-a-half hours after admission of treatment-resistant shock. The boy had at first only a low prothrombin value (39%), but later the other coagulation values also became abnormal. He died 16 hours after admission from the consumptive coagulopathy and profound anaemia (haemoglobin 7.4 g/dl, haematocrit 0.23). Neither patient had any clinical signs of meningitis. Isolation of Neisseria meningitidis from blood cultures confirmed the diagnosis.

Acute Disease↗
PubMed1991

The structure of bergenin.

X-ray analysis of the 3,4,8,10,11-penta-acetate (3) of bergenin has confirmed the earlier structural assignments.

Benzopyrans↗
PubMed1991

Role of the adhesion molecule ICAM-1 (CD54) in staphylococcal enterotoxin-mediated cytotoxicity.

Staphylococcal enterotoxin A (SEA) binds to major histocompatibility complex (MHC) class II molecules on target cells and directs human cytotoxic T lymphocytes (CTL) of irrelevant nominal specificity to mediate strong cytotoxicity against target cells. In this report we describe the importance of ICAM-1 (CD54) expression on the target cell in SEA-dependent cell-mediated cytotoxicity (SDCC), utilizing murine L cells co-transfected with HLA-DR and ICAM-1. Human CTL mediated a low but significant cytotoxicity against HLA-DR2- and HLA-DR7-transfected cells after preincubation with SEA, but no reactivity towards uncoated HLA-DR2 and HLA-DR7 cells or SEA-coated ICAM-1-transfected and untransfected L cells. In contrast, a strong cytotoxic response was mediated by CTL against L cells co-transfected with HLA-DR2/ICAM-1 and HLA-DR7/ICAM-1. Similar cytotoxic activity of the CTL was seen at a 30-fold lower effector-to-target cell ratio when comparing the HLA-DR2/ICAM-1-expressing cells with the HLA-DR2-expressing cells. SEA dose-response analysis demonstrated that the HLA-DR2/ICAM-1-expressing target cells enabled the CTL to respond to a 1000-fold lower concentration of SEA in comparison to the HLA-DR2-expressing cells. CD3+CD4+ and CD3+CD8+ cytotoxic T cell lines were equally dependent on the expression of ICAM-1 on the target cell. The strong CTL activity against HLA-DR2/ICAM-1-transfected cells could be blocked by anti-CD11a or anti-CD18 monoclonal antibodies (mAb), but not by anti-CD11b, anti-CD11c, anti-CD2 or unrelated control mAb. The great sensitivity of HLA-DR2/ICAM-1 expressing target cells to SDCC was strongly reduced by preincubation with various anti-ICAM-1 mAb but not by mAb against monomorphic HLA-DR or murine MHC class I determinants. The result in this study clearly demonstrates that efficient re-targeting of human CTL by SE is dependent on a proper interaction with the heterodimer CD11a/CD18 (Leu-CAMa, LFA-1) on the CTL and its target cell ligand ICAM-1.

Antibodies, Monoclonal↗
PubMed1991

Two types of chloride channels in hen colon epithelial cells identified by patch-clamp experiments.

Freshly isolated epithelial cells from hen colon were investigated using the patch-clamp technique. The aim of this investigation was to characterise the cellular conducting site for Cl- secretion. In cell-attached mode two types of Cl(-)-channels were found. Both showed distinct outward rectification. The channel types differed in single channel conductances and the marked voltage dependence of the open probabilities. A low conductance Cl(-)-channel was observed with a mean conductance at negative holding potentials of g- = 9 pS, and of g+ = 34 pS at positive potentials. This channel was predominantly open at negative potentials, corresponding to cell hyperpolarization. The second channel type observed had conductances of g- = 35 pS and g+ = 77 pS, and showed increasing open probabilities with increasing holding potentials (cell depolarisation). Both channel types were blockable by the Cl(-)-channel blocker NPPB. These data in combination with previously published transepithelial transport data on hen colon indicate that these channels are the Cl- secretory sites in colon epithelium.

Animals↗