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S Janssen

Publications and source records attributed to S Janssen.

At least 19 recordsLinked to original sources
PubMed2006

Ion transporters for fluid reabsorption in the rooster (Gallus domesticus) epididymal region.

Testicular fluid is highly condensed during its passage through the epididymal region in the avian species. In the present study, major ion transporters that are responsible for condensation mainly by water resorption in the reproductive tract as identified in the mammalian epididymis were localized within the rooster (Gallus domesticus) epididymis by immunohistochemistry. The results show that the efferent ductule epithelium expressed sodium-potassium ATPase (Na(+),K(+)-ATPase), carbonic anhydrase II (CAII) and sodium hydrogen exchanger isoform 3 (NHE3) and that the connecting ductule and epididymal duct epithelia expressed Na(+),K(+)-ATPase and CAII. These data suggest that a model proposed for reabsorption in mammalian efferent ductules can be applied to avian efferent ductules.

Absorption↗
PubMed2005

Orbital dynamics of the 4f shell in DyB2C2.

For the first time, fluctuations in the Dy quadrupole (orbital) moment have been observed in DyB(2)C(2) using inelastic neutron scattering. The observed quasielastic response is decomposed into two components, one reflecting transitions within the doublets (narrow) and the other transitions between the doublets (broad) of the effective Dy quartet ground state. The widths of the narrow and broad components are shown to arise from fluctuations in the magnetic dipole and the electric quadrupole moments, respectively.

Journal Article↗
PubMed2004

Photoproduction of eta-mesic 3He.

The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma3He-->etaX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonancelike structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasibound state. This is supported by studies of a competing decay channel of such a quasibound eta-mesic nucleus into pi(0)pX. A binding energy of (-4.4+/-4.2) MeV and a width of (25.6+/-6.1) MeV is deduced for the quasibound eta-mesic state in 3He.

Journal Article↗
PubMed2004

Origin of higher order magnetic exchange: evidence for local dimer exchange striction in CsMn0.28Mg0.72Br3 probed by inelastic neutron scattering.

The origin of higher-order exchange interactions in localized S-state systems has been the subject of intensive investigations in the past. In particular, it has been suggested that a biquadratic exchange term may arise from the magnetoelastic energy. Here we report on the pressure and temperature dependence of the excitation spectra of magnetic Mn2+ dimers in CsMn0.28Mg0.72Br3 probed by inelastic neutron scattering. Biquadratic exchange and a strong distance dependence of the bilinear exchange are observed. It is shown that the mechanism of local exchange striction may explain the occurrence of biquadratic exchange in accordance with the elastic properties of the compound.

Journal Article↗
PubMed2004

[Recurrent tumors in the oral and maxillofacial region. Results and treatment strategies in 20 years].

UNLABELLED: SUBJECT MATTER: Following clinical diagnosis of a recurrent tumor, curative treatment is seldom available. Depending on the size of the recurrent tumor and the patient's general health condition, extensive surgical resections and reconstructions are avoided in favor of nonsurgical treatment modalities with palliative intent. According to the literature, location of the tumor, tumor size and R-1 and R-2 resection rates are the most frequent reasons for the development of recurrent tumors. PATIENTS AND METHODS: In a retrospective evaluation, a population of 1000 patients who had been treated for primary head and neck cancer during the period from 1979 to 1996 were analyzed descriptively. Survival probabilities of patients with recurrent tumors were calculated according to the Kaplan-Meier product-limit method, and different treatment concepts were compared and analyzed with the log-rank test for significant differences. RESULTS: The largest proportion of primary tumors involved the floor of the mouth (n=369, 36.9%). A total of 198 patients (19.8%) developed recurrent cancer; 79.8% of patients experienced recurrent cancer within 2 years following primary treatment. Within the group of T1/T2 tumors the incidence of recurrent tumors was 28.9%, whereas the incidence in the T3/T4 group was 44.6%. Tumor infiltration of the resection margins was detected in 12.9%. CONCLUSIONS: In line with the literature, tumor infiltration of the resection margins is a relevant prognostic factor; therefore, intraoperative frozen section must be recommended. Treatment with curative intention, in particular extensive surgical resections, is seldom possible and always requires a very intensive discussion with the patient.

Adult↗
PubMed2004

Frostbite in a mountaineer.

Cold injury is an objective danger in mountain climbing as well as in many outdoor sports. With increasing number of people practising so-called extreme tourisms physicians can be confronted with frostbite. Thus we present a case of frostbite in a 35 year-old female mountaineer. She took part at a demanding high alpine trekking tour in the Himalayan-area requesting well trained mountaineers experienced in ice- and securing-techniques and good physical condition. At day 12, when the group reached the top of the Parchamo (Nepal, 6273 m), she developed frostbite at all toes leading to amputation finally. Risk factors, prognosis and options for initial treatment are discussed.

Adult↗
PubMed2002

The reaction gammap-->pi0gamma'p and the magnetic dipole moment of the Delta+ 1232 resonance.

The reaction gammap-->pi(0)gamma'p has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between sqrt[s]=1221-1331 MeV. The cross section's differential in angle and energy have been determined for the photon gamma' in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the Delta(+)(1232) resonance and, for the first time, a value of mu(Delta(+))=[2.7(+1.0)(-1.3)(stat)+/-1.5(syst)+/-3(theor)]mu(N) has been extracted.

Journal Article↗
PubMed2002

In-medium modifications of the pipi interaction in photon-induced reactions.

Differential cross sections of the reactions (gamma,pi(0)pi(0)) and (gamma,pi(0)pi(+/-)) have been measured for several nuclei (1H,12C, and (nat)Pb) at an incident-photon energy of E(gamma)=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the pipi invariant-mass distribution is found in the pi(0)pi(0) channel. This dependence is not observed in the pi(0)pi(+/-) channel and is consistent with an in-medium modification of the pipi interaction in the I=J=0 channel. The data are compared to pi-induced measurements and to calculations within a chiral-unitary approach.

Journal Article↗
PubMed2001

Specific targeting of insect and vertebrate telomeres with pyrrole and imidazole polyamides.

DNA minor groove-binding compounds (polyamides) that target insect and vertebrate telomeric repeats with high specificity were synthesized. Base pair recognition of these polyamides is based on the presence of the heterocyclic amino acids pyrrole and imidazole. One compound (TH52B) interacts uniquely and with excellent specificity (K(d) = 0.12 nM) with two consecutive insect-type telomeric repeats (TTAGG). A related compound, TH59, displays high specificity (K(d) = 0.5 nM) for tandem vertebrate (TTAGGG) and insect telomeric repeats. The high affinity and specificity of these compounds were achieved by bidentate binding of two flexibly linked DNA-binding moieties. Epifluorescence microscopy studies show that fluorescent derivatives of TH52B and TH59 stain insect or vertebrate telomeres of chromosomes and nuclei sharply. Importantly, the telomere-specific polyamide signals of HeLa chromosomes co-localize with the immunofluorescence signals of the telomere-binding protein TRF1. Our results demonstrate that telomere-specific compounds allow rapid estimation of relative telomere length. The insect-specific compound TH52 was shown to be incorporated rapidly into growing Sf9 cells, underlining the potential of these compounds for telomere biology and possibly human medicine.

Animals↗
PubMed2001

Magnetic polyoxometalates: anisotropic antiferro- and ferromagnetic exchange interactions in the pentameric cobalt(II) cluster.

The ground-state properties of the pentameric Co(II) cluster [Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)](12-) were investigated by combining magnetic susceptibility and low-temperature magnetization measurements with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na(12)[Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)].46D(2)O. The encapsulated magnetic Co(5) unit consists of three octahedral and two tetrahedral oxo-coordinated Co(II) ions. Thus, two different types of exchange interactions are present within this cluster: a ferromagnetic interaction between the octahedral Co(II) ions and an antiferromagnetic interaction between the octahedral and the tetrahedral Co(II) ions. As a result of the single-ion anisotropy of the octahedral Co(II) ions, the appropriate exchange Hamiltonian to describe the ground-state properties of the Co(5) spin cluster is anisotropic and is expressed as H = -2 summation operator(i= x,y,z)J(1)(i)[S(1)(i)S(2)(i) + S(2)(i)S(3)(i)] + J(2)(i)[S(1)(i)S(5)(i) + S(2)(i)S(5)(i) + S(2)(i)S(6)(i) + S(3)(i)S(6)(i)], where J(1)(i) are the components of the exchange interaction between the octahedral Co(II) ions and J(2)(i) are the components of the exchange interaction between the octahedral and tetrahedral Co(II) ions (see Figure 1d). The study of the exchange interactions in the two structurally related polyoxoanions [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10)(-) and [Co(3)W(H(2)O)(2)(ZnW(9)O(34))(2)](12)(-) allowed an independent determination of the ferromagnetic exchange parameters J(1)(x) = 0.70 meV, J(1)(y) = 0.43 meV, and J(1)(z) = 1.51 meV (set a) and J(1)(x) = 1.16 meV, J(1)(y) = 1.16 meV and J(1)(z) = 1.73 meV (set b), respectively. Our analysis proved to be much more sensitive to the size and anisotropy of the antiferromagnetic exchange interaction J(2). We demonstrate that this exchange interaction exhibits a rhombic anisotropy with exchange parameters J(2)(x) = -1.24 meV, J(2)(y) = -0.53 meV, and J(2)(z) = -1.44 meV (set a) or J(1)(x) = -1.19 meV, J(1)(y) = -0.53 meV, and J(1)(z) = -1.44 meV (set b). The two parameter sets reproduce in a satisfactory manner the susceptibility, magnetization, and INS properties of the title compound.

Journal Article↗
PubMed2001

Ferredoxins from the archaeon Acidianus ambivalens: overexpression and characterization of the non-zinc-containing ferredoxin FdB.

Two ferredoxin genes, fdA and fdB, from the extremely thermoacidophilic crenarchaeon Acidianus ambivalens have been sequenced; the sequences share 86% similarity. Whereas the deduced protein sequence of the ferredoxin FdA clearly contains a zinc-binding motif, the corresponding sequence of the FdB is devoid of this motif. Thus far, only the zinc-containing ferredoxin, FdA, from A. ambivalens has been chemically and functionally characterized from its native source. Using RT-PCR and Northern blot analysis, we show that both ferredoxins are expressed by A. ambivalens under either anaerobic or aerobic growth conditions. The zinc-free ferredoxin, FdB, was overexpressed in E. coli and purified to homogeneity. Using EPR spectroscopy, we could demonstrate that FdB contains one [3Fe-4S](1+/0) and one [4Fe-4S](2+/1+) cluster. The reduction potential of the [3Fe-4S](1+/0) cluster was determined as -235+/-10 mV, at pH 6.5, by EPR-monitored redox titration. The high melting temperature of 108+/-2 degrees C of FdB determined by CD spectroscopy reveals that it is not the binding of the Zn2+ that induces the extreme thermostability of these ferredoxins.

Amino Acid Sequence↗
PubMed2000

Chromatin opening of DNA satellites by targeted sequence-specific drugs.

There are few tools available for dissecting and elucidating the functions of DNA satellites and other nongenic DNA. To address this, we have explored the experimental potential of DNA sequence-specific drugs containing pyrrole and imidazole amino acids (polyamides). Compounds were synthesized that target different Drosophila melanogaster satellites. Dimeric oligopyrroles were shown to target the AT-rich satellites I, III, and SARs (scaffold associated regions). One polyamide (P31) specifically binds the GAGAA satellite V. Specificity of targeting was established by footprinting, epifluorescence of nuclei, and polytene chromosomes stained with fluorescent derivatives. These polyamides were shown to mediate satellite-specific chromatin opening of the chromatin fiber. Remarkably, certain polyamides induced defined gain or loss-of-function phenotypes when fed to Drosophila melanogaster.

AT Rich Sequence↗
PubMed2000

Specific gain- and loss-of-function phenotypes induced by satellite-specific DNA-binding drugs fed to Drosophila melanogaster.

DNA-binding pyrrole-imidazole compounds were synthesized that target different Drosophila melanogaster satellites. Compound P31 specifically binds the GAGAA satellite V, and P9 targets the AT-rich satellites I and III. Remarkably, these drugs, when fed to developing Drosophila flies, caused gain- or loss-of-function phenotypes. While polyamide P9 (not P31) suppressed PEV of white-mottled flies (increased gene expression), P31 (not P9) mediated three well-defined, homeotic transformations (loss-of-function) exclusively in brown-dominant flies. Both phenomena are explained at the molecular level by chromatin opening (increased accessibility) of the targeted DNA satellites. Chromatin opening of satellite III by P9 is proposed to suppress PEV of white-mottled flies, whereas chromatin opening of satellite V by P31 is proposed to create an inopportune "sink" for the GAGA factor (GAF).

AT Rich Sequence↗
PubMed1997

A succinate dehydrogenase with novel structure and properties from the hyperthermophilic archaeon Sulfolobus acidocaldarius: genetic and biophysical characterization.

The sdh operon of Sulfolobus acidocaldarius DSM 639 is composed of four genes coding for the 63.1-kDa flavoprotein (SdhA), the 36.5-kDa iron-sulfur protein (SdhB), and the 32.1-kDa SdhC and 14.1-kDa SdhD subunits. The four structural genes of the sdhABCD operon are transcribed into one polycistronic mRNA of 4.2 kb, and the transcription start was determined by the primer extension method to correspond with the first base of the ATG start codon of the sdhA gene. The S. acidocaldarius SdhA and SdhB subunits show characteristic sequence similarities to the succinate dehydrogenases and fumarate reductases of other organisms, while the SdhC and SdhD subunits, thought to form the membrane-anchoring domain, lack typical transmembrane alpha-helical regions present in all other succinate:quinone reductases (SQRs) and quinol:ifumarate reductases (QFRs) so far examined. Moreover, the SdhC subunit reveals remarkable 30% sequence similarity to the heterodisulfide reductase B subunit of Methanobacterium thermoautotrophicum and Methanococcus jannaschii, containing all 10 conserved cysteine residues. Electron paramagnetic resonance (EPR) spectroscopic studies of the purified enzyme as well as of membranes revealed the presence of typical S1 [2Fe2S] and S2 [4Fe4S] clusters, congruent with the deduced amino acid sequences. In contrast, EPR signals for a typical S3 [3Fe4S] cluster were not detected. However, EPR data together with sequence information implicate the existence of a second [4Fe4S] cluster in S. acidocaldarius rather than a typical [3Fe4S] cluster. These results and the fact that the S. acidocaldarius succinate dehydrogenase complex reveals only poor activity with caldariella quinone clearly suggest a unique structure for the SQR of S. acidocaldarius, possibly involving an electron transport pathway from the enzyme complex into the respiratory chain different from those for known SQRs and QFRs.

Amino Acid Sequence↗
PubMed1997

Reliability of five rapid D-dimer assays compared to ELISA in the exclusion of deep venous thrombosis.

Studies measuring the fibrin degradation product D-Dimer (DD) using enzyme-linked immunosorbent assays (ELISA) in patients with venographically proven deep venous thrombosis (DVT) suggest that it is possible to exclude DVT when DD level is below a certain cut-off level. However, ELISA methods are time-consuming and not available in all laboratories. Different rapid latex-agglutination assays have been investigated, but their sensitivity is considerably lower. In the present study we compared the value of four novel latex DD tests (Tinaquant, Minutex, Ortho and SimpliRed) and one rapid ELISA (VIDAS) to a classical ELISA DD assay (Organon Mab Y18) in 132 patients suspected of DVT. The VIDAS, a new quantitative automated ELISA, had a sensitivity of 100% and a negative predictive value of 100% for both proximal and distal DVT at a cut-off level of 500 ng/ml. The Tinaquant assay, a new quantitative latex method, had a sensitivity of 99% and a negative predictive value of 93% for both proximal and distal DVT at a cut-off level of 500 ng/ml. For proximal DVT only, both assays had a sensitivity and negative predictive value of 100%. VIDAS and Tinaquant correlated well with ELISA (correlation of r = 0.96 and r = 0.98 respectively). Sensitivities of the semi-quantitative latex assays Minutex, Ortho and SimpliRed were considerably lower (77%, 51% and 61% respectively). These results suggest that VIDAS and Tinaquant may be used instead of ELISA DD in the exclusion of DVT. Tinaquant can be performed within 20 min and VIDAS within 35 min. Both assays might be used as a routine screening test and should be evaluated in large clinical management studies.

Adult↗
PubMed1997

Detection of malignant cells of epithelial origin in mononuclear cell fractions.

Qualitative and quantitative detection of contaminating malignant cells in stem cell apheresis products intended for supportive therapy after high-dose chemotherapy of sensitive solid tumors is a demanding task for the laboratory. Human breast cancer cells in differing concentrations among mononuclear cells were quantitated by multicolor flow cytometry and immunocytochemistry. Comparing specificity, sensitivity, and laboratory processing time, the immunocytochemical detection of the above-mentioned malignant cells of epithelial origin was demonstrated to be the superior method.

Breast Neoplasms↗
PubMed1996

Effect of central administration of the kappa-opiate receptor agonist U 69.593 on neurohypophyseal hormone levels in blood and cerebrospinal fluid.

Intracerebroventricular (i.c.v.) administration of the kappa-opiate receptor agonist U 69.593 induces a rapid and short lasting suppression of oxytocin (OXT) levels in plasma of water deprived rats, whereas only a tendency towards a suppression of vasopressin (AVP) levels in plasma is observed. No change in neurohypophyseal hormone levels in CSF occurs following i.c.v. administration of U 69.593 at the various times points studied. It is concluded that, upon i.c.v. administration, the suppressive influence of U 69.593 is much weaker than that of the dynorphins and that neurophypophyseal hormone levels in CSF behave differently from those in the peripheral circulation.

Analgesics↗