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W Seidel

Publications and source records attributed to W Seidel.

At least 37 records · Page 2Linked to original sources
PubMed2000

Subpicosecond electro-optic measurement of relativistic electron pulses

Time-resolved measurements of the transverse electric field associated with relativistic electron bunches are presented. Using an ultrafast electro-optic sensor close to the electron beam, the longitudinal profile of the electric field was measured with subpicosecond time resolution and without time-reversal ambiguity. Results are shown for two cases: inside the vacuum beam line in the presence of wake fields, and in air behind a beryllium window, effectively probing the near-field transition radiation. Especially in the latter case, reconstruction of the longitudinal electron bunch shape is straightforward.

Journal Article↗
PubMed1999

N(2)-(1-Carboxyethyl)deoxyguanosine, a nonenzymatic glycation adduct of DNA, induces single-strand breaks and increases mutation frequencies.

N(2)-(1-Carboxyethyl)deoxyguanosine (CEdG) is a major nonenzymatic glycation product of DNA. The effect of CEdG modification, which was specifically prepared by incubation with dihydroxyacetone, on plasmid DNA topology was evaluated by gel electrophoresis. A time-dependent decrease of supercoiled plasmid-DNA was observed in parallel to the increase of CEdG adducts; the half-life time of the supercoiled plasmid-DNA was estimated to be approximately 16-18 h. CEdG-modified plasmid DNA showed a 25-fold reduced transformation efficiency. When modified DNA was used to transform Escherichia coli cells, a 6-fold increase in mutation frequency was determined by measuring loss of alpha-complementation. For the mutator strain BMH71-18mutS, an 8-fold increase in mutation frequency was observed. Although the exact mechanism of DNA damage is unclear, the occurrence of spontaneous depurination is likely. These findings suggest that a defined DNA glycation reaction can lead to DNA damage in vivo.

DNA Adducts↗
PubMed1999

The subgenus-specific C-terminal region of protein IX is located on the surface of the adenovirus capsid.

We have investigated the antigenicity of the C- and N-terminal halves of pIX of human adenovirus types 2 and 3 (Ad2 and Ad3) as well as their orientations in virions. We found that only the C-terminal halves of Ad2 pIX and Ad3 pIX reacted in a subgenus-specific manner by enzyme-linked immunosorbent assay and immunoblot analysis. Based on immunoelectron microscopy experiments, pIX in viral capsids appears to be positioned such that the C-terminal part of pIX constitutes the surface domain whereas the N terminus of the protein makes up the internal domain in icosahedral Ad capsids.

Adenoviruses, Human↗
PubMed1998

Immunochemical detection of N2-[1-(1-carboxy)ethyl]guanosine, an advanced glycation end product formed by the reaction of DNA and reducing sugars or L-ascorbic acid in vitro.

In the Maillard reaction, free amino groups of proteins and nucleic acids react with reducing sugars to form advanced glycation end products (AGE). A major product found in reaction mixtures of guanosine and glucose is N2-[1-(1-carboxy)ethyl]guanosine (CEG), which, therefore, can be used as a marker of advanced glycation of DNA. An enzyme-linked immunosorbent assay (ELISA) was developed to detect and to semi-quantitate nonenzymatic glycosylation of DNA. A polyclonal antiserum was raised against CEG linked to keyhole limpet hemocyanin. A protocol for a competitive ELISA was developed, and the antiserum was tested for crossreactivity. Several unmodified nucleotides and N2-modified guanosine derivatives showed no or negligible crossreactivity. Only very similar structures like N2-(carboxymethyl)guanosine and N2-(1-carboxy-3-hydroxypropyl)guanosine, which have been identified as reaction products of glucose or l-ascorbic acid and guanosine, display significant binding activity. The signal can be totally repressed by free CEG, yet protein-bound CEG is a stronger inhibitor. DNA incubated with d-glucose, dihydroxyacetone, l-ascorbic or l-dehydroascorbic acid shows a signal inhibition indicating the formation of CEG in vitro. The competitive ELISA procedure proved to be a sensitive method which can be used to detect glycation of DNA in vivo.

Amino Acids↗
PubMed1998

Reaction of guanosine with glucose under oxidative conditions.

Incubation of glucose with guanosine under oxidative conditions at 37 degrees C or 70 degrees C leads to the formation of a main product, which can be detected by HPLC/DAD. The compound was isolated and identified as N2-carboxymethyl-guanosine (CMG). To confirm the structure, CMG was also synthesized from glyoxal and guanosine.

Chromatography, High Pressure Liquid↗
PubMed1998

Adenovirus death protein, a transmembrane protein encoded in the E3 region, is palmitoylated at the cytoplasmic tail.

The 11.6-K protein of human adenovirus 2 (Ad2), which was recently renamed as adenovirus death protein (ADP), is a type III membrane glycoprotein that ultimately localizes to the nuclear membrane. ADP is encoded in the E3 transcription unit of Ad2 and migrates as a set of multiple bands in SDS-PAGE with three major forms. The corresponding gene product of adenovirus 5 (Ad5) has a slightly lower molecular weight and shows the same pattern in SDS-PAGE. We report here the covalent attachment of fatty acids to cysteine residues of ADP. In the case of Ad5-ADP all three major forms of this protein can be labeled by [3H]palmitic acid, but not by [3H]myristic acid, whereas only two [3H]palmitic acid-labeled Ad2-ADP species could be detected. The label is sensitive to treatment with 1 M hydroxylamine at pH 7 and with 20% beta-mercaptoethanol indicating that the fatty acids are linked via a thioester bond. By thin layer chromatography, the vast majority of the incorporated label was identified as palmitic acid. Two cysteine residues at the boundary between transmembrane domain and cytoplasmic tail which could serve as acceptor sites were mutated to alanine residues by site-directed mutagenesis of the cloned Ad5-ADP gene. Expression of wild-type Ad5-ADP and the resulting mutants was performed in HeLa cells using the vaccinia virus T7 expression system. As demonstrated by labeling with [3H]palmitic acid, only the mutants with one remaining cysteine residue in the cytoplasmic tail were able to incorporate [3H]palmitic acid, indicating that either could serve as acceptor site. In contrast the double cysteine mutant could not be labeled by [3H]palmitic acid, clearly demonstrating that cysteines 53 and 54 are required for palmitoylation and probably represent the palmitoylation sites in Ad5-ADP.

Adenoviridae↗
PubMed1998

Persistent parvovirus B19 infections in immunocompromised children.

Immunocompromised patients have been shown to suffer from prolonged viral infections often without detectable immune response. Here chronic infections with low virus levels can be frequently observed. In these patients viral DNA can be detected over long periods by polymerase chain reaction (PCR). In this study parvovirus B19 presence was assessed by PCR, immunoblot and enzyme-linked immunosorbent assay in sera from children with mainly oncological and hematological diseases. In 45% of sera B19 DNA was observed. Of the children 25% had IgG antibodies to viral protein 1 and 2 (VP1/2) and 15% to nonstructural protein 1 (NS1). In 6% of children IgM antibodies to VP1/2 were detected. These results indicate that the number of children with immune response to B19 proteins is distinctly lower than the number of children with B19 DNA. Transfusions of blood products might have been a possible route for B19 infection. Establishment and maintenance of a persistent parvovirus B19 infection with or without immune response are enhanced in the analyzed immunocompromised children in comparison with immunocompetent children. A persistence of B19 DNA was demonstrated up to 10 months in patients sera.

Adolescent↗
PubMed1998

Rapid identification of subgenera of human adenovirus by serological and PCR assays.

Bacterially expressed recombinant protein IX (pIX) of human adenovirus serotype 2 (Ad2) and 3 (Ad3) was evaluated for use as a subgenus-specific antigen by enzyme-linked immunosorbent assay (ELISA) and Western blotting. Patients sera positive by ELISA for the genus-specific adenovirus hexon antigen recognized the recombinant pIX of Ad2 and Ad3 in a subgenus-specific manner by both assays. Polyclonal rabbit serum raised against the recombinant Ad2pIX reacted strongly by indirect immunofluorescence assay, with Adl, 2 and 5 (subgenus C) but not with serotypes representing other subgenera. In a similar way, anti-Ad3pIX reacted with Ad3, 7, 11 and 14 (subgenus B), but not with serotypes representing other subgenera. A polymerase chain reaction showed that the complete pIX gene could be amplified in a subgenus specific fashion using primers specific for Ad3 (subgenus B), Ad2 (subgenus C), or Ad40/41 (subgenus F). The pIX gene from the available isolates of subgenus A, D and E was not amplified with these primers. The use of pIX-based serological assays is useful for subgenotyping as a primary screen of anti-Ad sera. It is much more rapid than the currently used neutralization assay or hemagglutination inhibition test. The application of anti-pIX sera by immunofluorescence and a pIX gene-based PCR are rapid methods which will improve subgenus identification of adenoviruses.

Adenovirus Infections, Human↗
PubMed1998

Receptor binding sites and antigenic epitopes on the fiber knob of human adenovirus serotype 3.

The adenovirus fiber knob causes the first step in the interaction of adenovirus with cell membrane receptors. To obtain information on the receptor binding site(s), the interaction of labeled cell membrane proteins to synthetic peptides covering the adenovirus type 3 (Ad3) fiber knob was studied. Peptide P6 (amino acids [aa] 187 to 200), to a lesser extent P14 (aa 281 to 294), and probably P11 (aa 244 to 256) interacted specifically with cell membrane proteins, indicating that these peptides present cell receptor binding sites. Peptides P6, P11, and P14 span the D, G, and I beta-strands of the R-sheet, respectively. The other reactive peptides, P2 (aa 142 to 156), P3 (aa 153 to 167), and P16 (aa 300 to 319), probably do not present real receptor binding sites. The binding to these six peptides was inhibited by Ad3 virion and was independent of divalent cations. We have also screened the antigenic epitopes on the knob with recombinant Ad3 fiber, recombinant Ad3 fiber knob, and Ad3 virion-specific antisera by enzyme-linked immunosorbent assay. The main antigenic epitopes were presented by P3, P6, P12 (aa 254 to 269), P14, and especially the C-terminal P16. Peptides P14 and P16 of the Ad3 fiber knob were able to inhibit Ad3 infection of cells.

Adenoviruses, Human↗
PubMed1998

DNA-glycation leads to depurination by the loss of N2-carboxyethylguanine in vitro.

D-Glucose reacts with nucleosides, mainly guanosine, and DNA in a similar way as with proteins, and DNA-bound advanced glycation endproducts (AGE) are formed. Guanosine (Gua) was incubated with D-glucose or dihydroxyacetone (DHA) under variation of temperature and reaction time, and the formation of the glycation products N2-carboxyethylguanosine (CEG) and N2-carboxymethylguanosine (CMG) was monitored by HPLC/DAD. DHA proved to be a very potent glycating agent which specifically produces CEG. When deoxyguanosine (dGua) was glycated under the same conditions, formation of the glycation product N2-carboxyethyldeoxyguanosine (CEdG) resulted in a significant decrease in stability of the N-glycosidic bond. As a consequence more than 25% of CEdG was hydrolysed to give the corresponding guanine derivative CEguanine, whereas unmodified dGua was stable under these conditions. Glycated DNA was then incubated and depurination by the loss of CEguanine was monitored by HPLC. Significant release of CEguanine was observed, whereas free guanine was neither formed from glycated nor from control DNA in detectable amounts. These data suggest that CEdG which is formed during the glycation of DNA in vitro causes increased depurination of DNA and produces abasic sites.

DNA↗
PubMed1997

HLA markers and prediction of clinical course and outcome in rheumatoid arthritis.

OBJECTIVE: To evaluate HLA markers as early prognostic factors for disease severity in rheumatoid arthritis (RA). METHODS: HLA genotyping was carried out in a retrospective analysis of 66 RA patients and in a prospective study of 55 RA patients and 87 healthy controls using polymerase chain reaction-based methods for HLA-DRB1 specificities, DR4 alleles, and their linked DQB1 alleles, as well as HLA-B27. The clinical course of RA was assessed by clinical and radiologic scores. The impact of HLA markers was evaluated by epidemiologic means in addition to modeling using multiple logistic regression analysis. RESULTS: Shared epitope-positive (HVR3+) DR4 alleles and the HVR3 amino acid cassette QKRAA were associated with RA in both longstanding (relative risk [RR] 3.34 and 3.19) and recent-onset (RR 2.1 and 2.37) RA. In longstanding RA, radiologic evidence of severe joint destruction (Larsen score > 1.62) was seen more often in HVR3 shared epitope-positive patients than in epitope-negative patients (odds ratio [OR] = 25.67, chi 2 = 13.59, P = 0.0003). Moreover, rank sum analysis of Larsen indices indicated significantly higher ranking for the presence of the RA-associated HVR3 cassettes (QKRAA, QRRAA) when expressed on a DR4 allele (P < 0.0001). In the prospective study, DR4-positive patients had a significantly increased risk (OR = 13.75, P = 0.00083) of developing bony erosions. In addition, HVR3 epitope-positive DR4-positive individuals had significantly higher Larsen indices than did epitope-negative patients (P = 0.0083). In particular, the presence of the HVR3 epitope on DR4 resulted in an increased a posteriori likelihood (0.91) of developing early erosive disease compared with an a priori risk of 0.62. Conversely, the likelihood decreased to a minimum of 0.35 when the HVR3 epitope was absent. CONCLUSION: While the contribution of HLA typing to establishing the diagnosis of RA is limited, HLA-DR genotyping and DR4 subtype determination provide valuable markers for the prognosis of joint destruction in RA.

Adolescent↗
PubMed1997

Adenovirus-receptor interaction with human lymphocytes.

Lymphocytes play a key role in cell-mediated immunity and are host cells for several viral and bacterial pathogens. Their importance in adenovirus (Ad) infections is not yet fully understood. The initial event, the attachment of Ad to lymphocytes and their subsets, was examined using flow cytometry. The study included analysis of stimulated T cells in binding assays with FITC-labeled Ad fiber. The results confirm that native peripheral lymphocytes express very small amounts of Ad receptors. Stimulation with PHA and interleukin 2 induced the expression. The presence of Ad DNA as a sign of internalization in stimulated cells was demonstrated using the polymerase chain reaction. The findings suggest that lymphocytes after stimulation can turn into target cells for Ad. This is particularly important if there are indications for persistence of Ad, and in the case of immunocompromised patients severe, life-threatening diseases can develop.

Adenoviruses, Human↗
PubMed1996

[Peritoneal and subcutaneous administration of cefazolin as perioperative antibiotic prophylaxis in colorectal operations. Prospective randomized comparative study of 200 patients].

The prophylactic effect of a intraoperative intraperitoneal and subcutaneous application of cefazolin versus a single shot i.v. prophylaxis was investigated. Additionally, we registered the concentration of cefazolin in the serum and the peritoneal fluid in 22 patients. We randomized 200 patients of whom 189 were included in the study. Ninety-two patients received the prophylaxis i.v. (group 1) and 97 topically (group 2). In 4 (2.1%) wound infections occurred [3(3.3%) group 1 and 1 (1.0%) in group 2]. The difference was not significant. The concentration of cefazolin in the serum was significantly higher at 1 h and 2 h postoperatively in group 2. We conclude that a topical application of antibiotics is possible to prevent surgical wound infection.

Aged↗
PubMed1996

Inhibition of cell adhesion to the virus by synthetic peptides of fiber knob of human adenovirus serotypes 2 and 3 and virus neutralisation by anti-peptide antibodies.

The fiber knob of adenovirus (Ad) causes the first step in the interaction of adenovirus with cell membrane receptors. To obtain information on the receptor binding site(s) several synthetic peptides derived from Ad2 and Ad3 fiber head sequences and their antisera were tested for interference with virus attachment to HeLa and FL cells and cell adhesion to viruses. The anti-peptide sera were also evaluated in ELISA and virus neutralisation test. Ad2 (of subgroup C) and Ad3 (of subgroup B) attachment was not significantly inhibited by peptides corresponding to the amino acid residues 535-554, 555-573, 562-582 of Ad2 fiber or 210-225, 267-283, 291-306 and 300-319 of Ad3 fiber. However, microplate pre-adsorbed Ad3 fiber residues 210-225 and 267-283 could bind FL and HeLa cells, and 1 mg/ml of Ad3 fiber residues 267-283 inhibited the cell adhesion to Ad3 virus to approximately 90%. This peptide may participate in the receptor binding site of Ad3 fiber. ELISA reactive anti-peptide antibodies against the homologous peptide and virus did not significantly reduce the cell adhesion to the immobilised virus or the virus attachment to cells, but in the neutralisation assay antibodies raised to Ad2 fiber residues 555-573 and 562-582 and Ad3 fiber residues 210-225 caused neutralisation of the homologous virus at serum dilutions of 1:500 and 1:32, respectively. The corresponding peptides and one further peptide of Ad2 fiber and two of Ad3 fiber seem to contain neutralisation epitopes.

Adenoviruses, Human↗