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Biomedical subjects

G Wagner

Publications and source records attributed to G Wagner.

At least 37 records · Page 2Linked to original sources
PubMed2002

Observation of optical Smith-Purcell radiation at an electron beam energy of 855 MeV.

Smith-Purcell radiation, generated when a beam of charged particles passes close to the surface of a diffraction grating, has been studied in the visible spectral range at wavelengths of 360 and 546 nm with the low emittance 855 MeV electron beam of the Mainz Microtron MAMI. The beam focused to a spot size of 4 microm (full width at half maximum) passed over optical diffraction gratings of echelle profiles with blaze angles of 0.8 degrees, 17.27 degrees, and 41.12 degrees and grating periods of 0.833 and 9.09 microm. Taking advantage of the specific emission characteristics of Smith-Purcell radiation a clear separation from background components, such as diffracted synchrotron radiation from upstream beam optical elements and transition radiation, was possible. The intensity scales with a modified Bessel function of the first kind as a function of the distance between electron beam and grating surface. Experimental radiation factors have been determined and compared with calculations on the basis of Van den Berg's theory [P.M. Van den Berg, J. Opt. Soc. Am. 63, 689 (1973)]. Fair agreement has been found for gratings with large blaze angles while the measurement with the shallow grating (blaze angle 0.8 degrees ) is at variance with this theory. Finally, the optimal operational parameters of a Smith-Purcell radiation source in view of already existing powerful undulator sources are discussed.

Journal Article↗
PubMed2002

Bacteriorhodopsin crystal growth in reduced gravity--results under the conditions, given in CPCF on board of a Space Shuttle, versus the conditions, given in DCAM on board of the Space Station Mir.

For the purpose of bio-electronics, bacteriorhodopsin was crystallized into two habits through liquid-liquid-diffusion, namely individual needles of up to 1.9 mm in length and needle bunch-like clusters of up 4.9 mm in total length. In both the reduced gravity experiments performed, the morphology of the individual needles (crystal form A) had improved in terms of sharp needle edges and compact needle packing, compared to the parallel ground controls. For the long duration wide range low gravity condition in the "Diffusion-controlled Crystallization Apparatus for Microgravity (DCAM)" on Mir (STS-89 up), needle bunches on average were longer there than on the ground, while the compactness of the clusters, i.e. the average ratio of clustered length to clustered width was the reverse. Some exceptionally large individuals needles were grown in DCAM. For the "Commercial Protein Crystallization Facility (CPCF)" in short duration high definition microgravity conditions during a science mission of the Space Shuttle Discovery (STS-95), size and shape of the individual needles were homogeneous and superior to those of both the parallel ground controls and the results in DCAM. In CPCF, the average volume of the individual needles in suspension was increased by 50% in microgravity compared to those in the ground control.

Ammonium Sulfate↗
PubMed2002

[Subjective family image in anorexia nervosa and bulimia nervosa in adolescence: a controlled study].

OBJECTIVES: The family environments of patients with eating disorders have been studied extensively in recent decades. The "Subjective Family Image Test" is an instrument developed especially to measure differential perceptions by family members. Assessments of subjective family image in families of adolescents by means of this test have been carried out in only a few samples. METHODS: We aimed first to investigate subjective perceptions by adolescents of their family relations in a larger clinical sample of female adolescents (n = 118) suffering from anorexia nervosa of either subtype or from bulimia nervosa and to compare these perceptions with those of healthy controls (n = 96). Second we investigated intra-familial differences in perception. RESULTS: The main findings were that bulimia nervosa patients perceived lower individual autonomy and lower emotional connectedness than all other groups, the adolescents with bulimia perceived significantly lower autonomy and emotional connectedness within the family than their fathers, and the restrictive anorexia nervosa patients perceived higher connectedness than their fathers. The relevance of these findings for understanding family dynamics are discussed.

Adolescent↗
PubMed2002

A shared care approach to the management of erectile dysfunction in the community.

Erectile dysfunction (ED) affects men of all ages and results in considerable distress and impact on quality of life for those who suffer from it. As ED is associated with a wide variety of under-lying conditions and cardiovascular co-morbidities, there is a requirement for diversity of treatment options and several factors must be considered to customise and optimise therapy. In the ideal holistic approach to management of the ED patient, both primary care and specialist physicians have an important role to play. This article reports on a sequential approach for the diagnosis and treatment of ED, with an emphasis on 'shared care'. The deliberations are based on a pan-European inter-disciplinary group that met at the Lygon Arms, UK on 22 February 2002.

Erectile Dysfunction↗
PubMed2002

Morphological and functional characterization of a rat vaginal smooth muscle sphincter.

The aim of the present study was to gain information about adrenergic-, cholinergic- and non-adrenergic, non-cholinergic (NANC)- transmitter systems/mediators in the rat vagina, and to characterize its smooth muscles functionally. Tissue sections from vagina of Sprague Dawley rats were immunolabelled with antibodies against protein gene product 9.5 (PGP), synaptophysin (Syn), tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Circularly cut vaginal smooth muscle preparations from the distal vagina were studied in organ baths. In the paravaginal tissue, a large number of PGP-, NOS-, TH-, VIP-immunoreactive (IR) and few CGRP-IR nerve trunks were observed, giving off branches to the smooth muscle wall. The smooth muscle wall was supplied by a large number of PGP-, Syn-, VAChT-, NPY-, NOS- and TH- IR nerve terminals, whilst only a moderate to few numbers of CGRP-, VIP- and PACAP-IR terminals were identified. Especially the distal part of the vaginal wall, where the circularly running smooth muscle was thickened into a distinct sphincter structure, was very richly innervated, predominantly by PGP- and NOS-IR terminals. Below and within the basal parts of the epithelium in the distal half of the vagina, a large number of PGP- and few NOS- and PACAP-IR varicose terminals were observed. The vaginal arteries were encircled by plexuses of nerve terminals. A large number of these were PGP-, Syn-, VAChT-, NOS-, TH-, NPY- and VIP-IR, and few were CGRP- and PACAP-IR. In isolated preparations of the distal vagina, electrical field stimulation (EFS) caused frequency-dependent contractions, which were reduced by sildenafil, tetrodotoxin (TTX) and phentolamine. In preparations contracted by norepinephrine (NA), EFS produced frequency-dependent relaxations. Pretreatment with the NOS-inhibitor N(G)-nitro-L-arginine, TTX, or the inhibitor of soluble guanylate cyclase, ODQ, abolished the EFS relaxations. In NE precontracted preparations, cumulative addition of sildenafil caused concentration-dependent relaxation. Carbachol contracted the strips concentration-dependently from baseline. It can be concluded that the distal part of the rat vagina forms a distinct smooth muscle sphincter, which is richly innervated by adrenergic, cholinergic and NANC nerves. The present studies suggest that in the rat the L-arginine/NO-system not only plays an important role in the regulation of vaginal smooth muscle tone, but also affects blood flow, and may have sensory functions.

Acetylcholinesterase↗
PubMed2002

Heterologous expression and characterization of recombinant phytochrome from the green alga Mougeotia scalaris.

The full-length apoprotein (124 kDa) and the chromophore-binding N-terminal half (66 kDa) of the phytochrome of the unicellular green alga Mougeotia scalaris have been heterologously expressed in the methylotrophic yeast Pichia pastoris. Assembly with the tetrapyrrole phycocyanobilin (PCB) yielded absorption maxima (for the full-length protein) at 646 and 720 nm for red- and far-red absorbing forms of phytochrome (Pr and Pfr), respectively, whereas the maxima of the N-terminal 66 kDa domain are slightly blueshifted (639 and 714 nm, Pr and Pfr, respectively). Comparison with an action spectrum reported earlier gives evidence that in Mougeotia, as formerly reported for the green alga Mesotaenium caldariorum, PCB constitutes the genuine chromophore. The full-length protein, when converted into its Pfr form and kept in the dark, reverted rapidly into the Pr form (lifetimes of 1 and 24 min, ambient temperature), whereas the truncated chromopeptide (66 kDa construct) was more stable and converted into Pr with time constants of 18 and 250 min. Also, time-resolved analysis of the light-induced Pfr formation revealed clear differences between both recombinant chromoproteins in the various steps involved. The full-length phytochrome showed slower kinetics in the long milliseconds-to-seconds time domain (with dominant Pfr formation processes of ca 130 and 800 ms), whereas for the truncated phytochrome the major component of Pfr formation had a lifetime of 32 ms.

Base Sequence↗
PubMed2001

Distribution of lanthanoids, Be, Bi, Ga, Te, Tl, Th and U on the territory of Bulgaria using Populus nigra 'Italica' as an indicator.

The concentrations of lanthanoids, Be, Bi,Ga, Te, Tl, Th and U have been determined using ICP-MS for 100 standardized samples of poplar leaves collected from the territory of Bulgaria. The investigated elements are log-normally distributed on the territory. Using cluster analysis of the analytical data the samples were grouped according soil type on which the plants are growing.

Bulgaria↗
PubMed2001

Coupling particles and fields in a diffusive hybrid model.

A general scheme to patch together discrete and continuous descriptions of diffusion within the same physical space is studied. In the discrete description, diffusion is described by microscopic random walkers on a lattice; in the continuous description, diffusion is described through the macroscopic diffusion equation. The coupling scheme is based on the mutual exchange of mass flux across the discrete-continuous interface. Detailed tests of the scheme, coupling particle, and field descriptions are particularly illustrative for the diffusion problem. Both the nonequilibrium transport behavior and the equilibrium fluctuations of the combined discrete-continuous system are in agreement with theoretical predictions.

Journal Article↗
PubMed2001

Molecular dissection of the CD2-CD58 counter-receptor interface identifies CD2 Tyr86 and CD58 Lys34 residues as the functional "hot spot".

The heterophilic CD2-CD58 adhesion interface contains interdigitating residues that impart high specificity and rapid binding kinetics. To define the hot spot of this counter-receptor interaction, we characterized CD2 adhesion domain variants harboring a single mutation of the central Tyr86 or of each amino acid residue forming a salt link/hydrogen bond. Alanine mutations at D31, D32 and K34 on the C strand and K43 and R48 on the C' strand reduce affinity for CD58 by 47-127-fold as measured by isothermal titration calorimetry. The Y86A mutant reduces affinity by approximately 1000-fold, whereas Y86F is virtually without effect, underscoring the importance of the phenyl ring rather than the hydroxyl moiety. The CD2-CD58 crystal structure offers a detailed view of this key functional epitope: CD2 D31 and D32 orient the side-chain of CD58 K34 such that CD2 Y86 makes hydrophobic contact with the extended aliphatic component of CD58 K34 between CD2 Y86 and CD58 F46. The elucidation of this hot spot provides a new target for rational design of immunosuppressive compounds and suggests a general approach for other receptors.

Amino Acid Substitution↗
PubMed2001

Converting a DNA damage checkpoint effector (UmuD2C) into a lesion bypass polymerase (UmuD'2C).

During the SOS response of Escherichia coli to DNA damage, the umuDC operon is induced, producing the trimeric protein complexes UmuD2C, a DNA damage checkpoint effector, and UmuD'2C (DNA polymerase V), which carries out translesion synthesis, the basis of 'SOS mutagenesis'. UmuD'2, the homodimeric component of DNA pol V, is produced from UmuD by RecA-facilitated self-cleavage, which removes the 24 N-terminal residues of UmuD. We report the solution structure of UmuD'2 (PDB ID 1I4V) and interactions within UmuD'-UmuD, a heterodimer inactive in translesion synthesis. The overall shape of UmuD'2 in solution differs substantially from the previously reported crystal structure, even though the topologies of the two structures are quite similar. Most significantly, the active site residues S60 and K97 do not point directly at one another in solution as they do in the crystal, suggesting that self-cleavage of UmuD might require RecA to assemble the active site. Structural differences between UmuD'2 and UmuD'- UmuD suggest that UmuD'2C and UmuD2C might achieve their different biological activities through distinct interactions with RecA and DNA pol III.

Amino Acid Sequence↗
PubMed2001

Electron-transfer reactivity and enzymatic activity of hemoglobin in a SP Sephadex membrane.

Hemoglobin can exhibit a direct electron-transfer reaction after being entrapped in a SP Sephadex membrane. A pair of stable and well-defined redox waves are obtained at a hemoglobin-SP sephadex modified pyrolytic graphite electrode. The anodic and cathodic peak potentials are located at -0.244 and -0.336 V (vs SCE), respectively. On the other hand, the peroxidase activity of the protein in the membrane is also greatly enhanced. The apparent Michaelis-Menten constant is calculated to be 1.9 mM, which shows a large catalytic activity of hemoglobin in the SP Sephadex membrane toward hydrogen peroxide (H2O2). According to the direct electron-transfer property and enhanced peroxidase activity of Hb in the membrane, a Hb/SP Sephadex membrane-based H2O2 biosensor is prepared, with a linear range approximately 5.0 x 10(-6) to 1.6 x 10(-4) mol/L.

Animals↗
PubMed2001

Mechanisms contributing to T cell receptor signaling and assembly revealed by the solution structure of an ectodomain fragment of the CD3 epsilon gamma heterodimer.

The T cell receptor (TCR) consists of genetically diverse disulfide-linked alpha and beta chains in noncovalent association with the invariant CD3 subunits. CD3 epsilon and CD3 gamma are integral components of both the TCR and pre-TCR. Here, we present the solution structure of a heterodimeric CD3 epsilon gamma ectodomain complex. A unique side-to-side hydrophobic interface between the two C2-set immunoglobulin-like domains and parallel pairing of their respective C-terminal beta strands are revealed. Mutational analysis confirms the importance of the distinctive linkage as well as the membrane proximal stalk motif (RxCxxCxE) for domain-domain association. These biochemical and structural analyses offer insights into the modular pairwise association of CD3 invariant chains. More importantly, the findings suggest how the rigidified CD3 elements participate in TCR-based signal transduction.

Amino Acid Sequence↗
PubMed2001

Solution structure of DFF40 and DFF45 N-terminal domain complex and mutual chaperone activity of DFF40 and DFF45.

Apoptotic DNA fragmentation is mediated by a caspase-activated DNA fragmentation factor (DFF)40. Expression and folding of DFF40 require the presence of DFF45, which also acts as a nuclease inhibitor before DFF40 activation by execution caspases. The N-terminal domains (NTDs) of both proteins are homologous, and their interaction plays a key role in the proper functioning of this two-component system. Here we report that the NTD of DFF45 alone is unstructured in solution, and its folding is induced upon binding to DFF40 NTD. Therefore, folding of both proteins regulates the formation of the DFF40/DFF45 complex. The solution structure of the heterodimeric complex between NTDs of DFF40 and DFF45 reported here shows that the mutual chaperoning includes the formation of an extensive network of intermolecular interactions that bury a hydrophobic cluster inside the interface, surrounded by intermolecular salt bridges.

Amino Acid Sequence↗
PubMed2001

[Analgesics-induced chronic renal failure in patients on dialysis therapy in Hungary].

In recent years elaboration of the diagnosis of analgesic-nephropathy (ANP) with the help of imaging techniques significantly increased the possibility of diagnosing the disease. Therefore, evaluating the prevalence of ANP has become more accurate in our country as well. The prevalence of ANP has been investigated in patients who have newly been taken into the dialysis program due to renal disease of unknown aetiology in 22 dialysis centers between December 1994-December 1997. The diagnosis of ANP has been based on revealing chronic drug abuse in the history and positive results of renal imaging (decrease in length of both kidneys combined with either bumpy contours and/or papillary calcification). Among 284 patients dialysed with unknown diagnosis 42 (14.8% of all cases) proved to have ANP. All patients except 2 took analgesic mixtures containing phenacetin/paracetamol, phenason derivatives, acetilsalysilic acid, caffeine and/or codeine. According to their investigations, ANP is a common disease resulting in end-stage renal failure in Hungary as well.

Acetaminophen↗
PubMed2001

Recruitment of the transcriptional machinery through GAL11P: structure and interactions of the GAL4 dimerization domain.

The GAL4 dimerization domain (GAL4-dd) is a powerful transcriptional activator when tethered to DNA in a cell bearing a mutant of the GAL11 protein, named GAL11P. GAL11P (like GAL11) is a component of the RNA-polymerase II holoenzyme. Nuclear magnetic resonance (NMR) studies of GAL4-dd revealed an elongated dimer structure with C(2) symmetry containing three helices that mediate dimerization via coiled-coil contacts. The two loops between the three coiled coils form mobile bulges causing a variation of twist angles between the helix pairs. Chemical shift perturbation analysis mapped the GAL11P-binding site to the C-terminal helix alpha3 and the loop between alpha1 and alpha2. One GAL11P monomer binds to one GAL4-dd dimer rendering the dimer asymmetric and implying an extreme negative cooperativity mechanism. Alanine-scanning mutagenesis of GAL4-dd showed that the NMR-derived GAL11P-binding face is crucial for the novel transcriptional activating function of the GAL4-dd on GAL11P interaction. The binding of GAL4 to GAL11P, although an artificial interaction, represents a unique structural motif for an activating region capable of binding to a single target to effect gene expression.

Alanine↗
PubMed2001

Structural basis for the functional switch of the E. coli Ada protein.

The Escherichia coli protein Ada specifically repairs the S(p) diastereomer of DNA methyl phosphotriesters in DNA by direct and irreversible transfer of the methyl group to its own Cys 69 which is part of a zinc-thiolate center. The methyl transfer converts Ada into a transcriptional activator that binds sequence-specifically to promoter regions of its own gene and other methylation resistance genes. Ada thus acts as a chemosensor to activate repair mechanisms in situations of methylation damage. Here we present a highly refined solution structure of the 10 kDa N-terminal domain, N-Ada10, which reveals structural details of the nonspecific DNA interaction of N-Ada10 during the repair process and provides a basis for understanding the mechanism of the conformational switch triggered by methyl transfer. To further elucidate this, EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near-edge structure) data were acquired, which confirmed that the zinc-thiolate center is maintained when N-Ada is methylated. Thus, ligand exchange is not the mechanism that enhances sequence-specific DNA binding and transcriptional activation upon methylation of N-Ada. The mechanism of the switch was further elucidated by recording NOESY spectra of specifically labeled methylated-Ada/DNA complexes, which showed that the transferred methyl group makes many contacts within N-Ada but none with the DNA. This implies that methylation of N-Ada induces a structural change, which enhances the promoter affinity of a remodeled surface region that does not include the transferred methyl group.

Bacterial Proteins↗
PubMed2001

Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides.

A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3P=CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4[NH=C(Me)ON=CR1R2]2] [R1R2 = Me2, (CH2)4, (CH2)5, (Me)C(Me)=NOH], [PtCl4[NH=C(Me)ONR2]2] (R = Me, Et, CH2Ph), (R1 = H; R2 = Ph or C6H4Me; R3 = Me) as well as anionic-type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5[NH=C(Me)ON=CR2]] [R2 = Me2, (CH2)4, (CH2)5] and 1 equiv of Ph3P=CHCO2R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Delta4-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and 1H, 13C[1H], 31P[1H] and 195Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2[NH=C(Me)ON=CMe2]2] [crystal system tetragonal, space group P4(2)/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph3PCH2CO2Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna2(1) (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph3P=CHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.

Journal Article↗