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Biomedical subjects

U Vogel

Publications and source records attributed to U Vogel.

At least 73 records · Page 4Linked to original sources
PubMed1997

Complement factor C3 deposition and serum resistance in isogenic capsule and lipooligosaccharide sialic acid mutants of serogroup B Neisseria meningitidis.

Serogroup B meningococci express sialic acids on their surfaces as a modification of the lipooligosaccharide (LOS) and as capsular material consisting of alpha2,8-linked sialic acid homopolymers. The aim of this study was to elucidate the impact of each sialic acid component on the deposition of complement factor C3 and serum resistance. For this purpose, we used isogenic mutants deficient in capsule expression (a polysialyltransferase mutant) or sialylation of the LOS (a galE mutant) or both (a mutant with a deletion of the cps gene locus). Bactericidal assays using 40% normal human serum (NHS) demonstrated that both the capsule and LOS sialic acid are indispensable for serum resistance. By immunoblotting with monoclonal antibody MAb755 that is specific for the C3 alpha-chain, we were able to demonstrate that C3 from 40% NHS was covalently linked to the surface structures of meningococci as C3b and iC3b, irrespective of the surface sialic acid compounds. However, C3b linkage was more pronounced and occurred on a larger number of target molecules in galE mutants with nonsialylated LOS than in meningococci with wild-type LOS, irrespective of the capsule phenotype. C3b deposition was caused by both the classical pathway (CP) and the alternative pathway of complement activation. Use of 10% NHS revealed that at low serum concentrations, C3 deposition occurred via the CP and was detected primarily on nonsialylated-LOS galE mutants, irrespective of the capsular phenotype. Accordingly, immunoglobulin M (IgM) binding to meningococci from heat-inactivated NHS was demonstrated only in both encapsulated and unencapsulated galE mutants. In contrast, inhibition of IgA binding required both encapsulation and LOS sialylation. We conclude that serum resistance in wild-type serogroup B meningococci can only be partly explained by an alteration of the C3b linkage pattern, which seems to depend primarily on the presence of wild-type LOS, since a serum-resistant phenotype also requires capsule expression.

Bacterial Capsules↗
PubMed1996

Ectopic prostatic tissue in the spleen.

Ectopic prostatic tissue was found in the spleen in a 49-year-old white man who died of wide-spread malignant mesothelioma. The prostatic origin of the tissue was affirmed by positive immunohistochemical staining for prostatic specific antigen and prostatic acid phosphatase.

Choristoma↗
PubMed1996

Avoiding artifacts in the infant rat model for bacterial meningitis: use of Sangur test strips for the rapid quantification of blood contamination in cerebrospinal fluid.

The infant rat model is widely used to study the pathogenesis of meningitis caused by a variety of gram-positive and gram-negative bacteria. However, the interpretation of published results concerning meningitis is difficult in many records because the fact that blood contamination of the cerebrospinal fluid (CSF) cannot be avoided during the traumatic puncture procedure has not been taken into consideration. Since bacterial invasion of the central nervous system develops following bacteremia in this model, blood contamination of the CSF leads to a falsification of the CSF bacterial counts. Here we present an evaluation of a rapid and quantitative test for CSF blood contamination using Sangur test strips. The procedure requires minimal amounts of CSF and allows direct calculation of the CSF bacterial load due to blood contamination and, thus, provides refined criteria for the presence of bacterial meningitis in the infant rat model. It is superior to the detection of erythrocytes using a hemocytometer since it is less time consuming. Furthermore, we demonstrate the value of this method for the experimental infection of rats with Neisseria meningitis.

Animals↗
PubMed1996

Sialic acids of both the capsule and the sialylated lipooligosaccharide of Neisseria meningitis serogroup B are prerequisites for virulence of meningococci in the infant rat.

We investigated the contribution of the polysialic acid capsule and of terminal lipooligosaccharide (LOS) sialylation to the pathogenicity of Neisseria meningitidis in vivo using a set of defined isogenic mutants of the N. meningitidis strain B 1940 deficient in either capsule synthesis or LOS sialylation. Furthermore a spontaneous capsule-deficient variant was investigated, which was capable of switching on the capsule synthesis at a frequency of 3 x 10(-3) in vitro. Infection of infant rats with the wild-type strain revealed a high potential to cause bacteremia. This potential was attenuated in the capsule-phase variable mutant (LOS sialylation+). However, using a mutant irreversibly deficient in capsule synthesis, but expressing a sialylated LOS, bacteremia could only be achieved using 10(6) times higher numbers of bacteria when compared to the wild-type. The unencapsulated bacteria were located extracellularly upon examination of blood smears, suggesting that defense mechanisms, i.e. phagocytosis, directed against unencapsulated meningococci were exhausted using very high infecting doses. Interestingly, when infant rats were infected with encapsulated meningococci which were unable to sialylate the LOS, bacteremia could never be achieved, even with an infective dose as high as 10(8) colony forming units (CFU). Despite the presence of capsular polysaccharide this mutant was phagocytosed by peritoneal phagocytes, as was the unencapsulated, LOS-sialylated mutant, suggesting that the inability to cause bacteremia was due to a higher susceptibility to the action of the complement system, which is virtually unsaturable. We conclude that in the infant rat model of meningococcal infection both forms of sialic acid on the bacterial cell surface are indispensable for systemic survival.

Animals↗
PubMed1996

Increased endothelin release by cultured human smooth muscle cells from atherosclerotic coronary arteries.

OBJECTIVES: Endothelin, a 21-amino acid peptide initially purified from the medium of cultured endothelial cells, is a potent vasoconstrictor exerting its effects predominantly in a paracrine or autocrine manner. Recent data indicate that endothelin is also synthesized by cultured vascular smooth muscle cells and that endothelin is an effective stimulator of smooth muscle cell proliferation. This study aimed to investigate the endothelin release of cultured human smooth muscle cells, isolated from coronary plaques and from normal coronary tunica media, and to determine circulating endothelin concentrations in patients with coronary artery disease compared to control subjects. METHODS: Coronary plaque material was extracted by thrombendarterectomy during aorto-coronary bypass grafting (n = 19). Segments of normal coronary arteries were obtained at autopsy (n = 33). Cells were isolated by enzymatic disaggregation and identified as smooth muscle cells with antibodies against smooth muscle alpha-actin. Venous blood samples were drawn from patients with coronary artery disease undergoing cardiac catheterization (n = 32) and from control subjects (n = 38). Endothelin concentrations in culture medium and in plasma samples were measured by radioimmunoassay after Sep Pak C18 extraction. RESULTS: Cultured smooth muscle cells, isolated from coronary plaques, released a significantly (P < 0.001) higher amount of immunoreactive endothelin into the culture medium (39.2 +/- 3.9 pg/10(4) cells, mean +/- s.e.m., 31 supernatant samples) than smooth muscle cells from normal coronary tunica media (3.9 +/- 0.8 pg/10(4) cells, 28 samples). Circulating endothelin concentrations were slightly elevated (P < 0.01) in patients with coronary artery disease (3.8 +/- 0.2 pg/ml) compared to control subjects (3.0 +/- 0.2 pg/ml). CONCLUSIONS: These data suggest that the endothelin production is markedly increased in smooth muscle cells of coronary atherosclerotic plaques. The enhanced endothelin release may stimulate smooth muscle cell proliferation in a paracrine or autocrine manner and thus may contribute to the development or progression of coronary artery disease.

Cells, Cultured↗
PubMed1996

Predictive value of magnetic resonance imaging and computerized tomography for conservative renal surgery in an ex vivo tumor enucleation study followed by step-sectioning.

PURPOSE: Due to the early diagnosis of many renal cell cancers, the treatment options of organ conserving surgery is of interest even for patients with a normal contralateral kidney. To our knowledge the predictive value of preoperative investigations in such patients has not been clarified. MATERIALS AND METHODS: In a prospective study of 30 patients with stage T1/T2 renal cell carcinoma ex vivo enucleation was performed following tumor nephrectomy. Magnetic resonance imaging (MRI) and computerized tomography (CT) were done preoperatively in all patients. For pathological evaluation the kidneys were step-sectioned in 1 mm. slices. Macroscopic and microscopic findings were compared to those of the preoperative investigations. RESULTS: Mean tumor diameter was 4.6 cm. (range 2.0 to 10.0). Twelve tumors were incidental and smaller than 4 cm. Residual carcinoma due to incomplete resection was found in 4 kidneys with tumors larger than 4 cm. Parenchymal or hilar venous invasion was noted in 4 cases, including 1 in the incidental group. Prediction of renal fat capsule invasion by MRI was highly confirmed by pathological examination. On the other hand, parenchymal venous involvement or secondary renal tumors smaller than 2 cm. could not be predicted by MRI or CT. CONCLUSIONS: Neither MRI nor CT predicts complete tumor control when conservative renal surgery is considered. All incidental tumors smaller than 4 cm. could be resected completely by nephron sparing surgery. Nevertheless, microscopic venous invasion was present in 1 of the latter cases.

Adult↗
PubMed1995

Effects of the antiterminator BoxA on transcription elongation kinetics and ppGpp inhibition of transcription elongation in Escherichia coli.

It has been shown previously that two different mRNA chains (lacZ and infB) are elongated at a rate of approximately 40 nucleotides (nt)/s during steady state growth on minimal medium and that the rate of mRNA chain elongation is inhibited by ppGpp in vivo. On the other hand, it was found that a truncated ribosomal RNA chain was elongated at a rate of approximately 80 nt/s, independent of growth condition (Vogel, U., and Jensen, K. F. (1994) J. Biol. Chem. 269, 16236-16241). We reasoned that the different transcriptional behavior of mRNA genes and rRNA operons might be caused by the antiterminator sequences present in the rRNA operons. To test this possibility, we have (a) inserted the minimal antiterminator boxA sequence between the promoter and the lacZ and infB genes and (b) deleted the antiterminator sequences from the rRNA transcription unit and measured transcription elongation rates in vivo on the resulting hybrid genes. We found that insertion of boxA in front of the coding region of lacZ increased the transcription elongation rate from 42 nt/s to 69 nt/s during steady state growth and that it eliminated the ppGpp-dependent decrease in the transcription elongation rate during the stringent response. On the other hand, deletion of the antiterminator sequences from the rRNA operon resulted in a reduced transcription elongation rate, but the elongation rate was still insensitive to changes in the ppGpp pool. These results are consistent with the hypothesis that the antiterminator boxA is a primary determinant of the rate of transcription elongation rate.

Base Sequence↗
PubMed1995

Transcriptional activation of psoriasis-associated cytokeratin K17 by interferon-gamma. Analysis of gamma-interferon activation sites.

The acid cytokeratin K17 is inducible by interferon-gamma (IFN-gamma), a characteristic unique for cytokeratins analysed so far. In this report, we analysed the molecular basis of K17 expression by IFN-gamma in epithelial cells. The 5'-flanking region of the K17 gene (positions -1762 to -13), cloned in front of a chloramphenicol acetyl transferase (CAT) reporter gene construct, conferred responsiveness to IFN-gamma but not IFN-alpha in transient transfection assays. Sequence analysis revealed three putative gamma-interferon activation sites (GAS). Band-shift assays and transient transfections with CAT reporter gene constructs were used to characterize and to dissect the functional importance of each of the putative GAS elements. In the band shift assay, GAS3 (positions -1528 to -1515) was found to bind GAF/STAT91 and to compete with tryptophanyl-tRNA synthetase (IFP53/WRS)-GAS for binding to GAF; in contrast, GAS1 (positions -183 to -171) and GAS2 (positions -290 to -277) were neither able to bind to nor to compete for GAF/STAT91. However, deletion constructs and mutational analysis of CAT reporter gene constructs harbouring the 5'-flanking region (positions -1762 to -111) in front of the heterologous promoter revealed that the distal GAS3 site was dispensible, but that alteration of the GAS1 element rendered the promoter uninducible by IFN-gamma. Surprisingly, transfection of a CAT-reporter gene construct harbouring a promoter segment (positions -111 to +13) devoid of the GAS elements revealed enhanced CAT-gene expression upon IFN-gamma treatment. The interaction of GAS1 with the interferon-responsive promoter region in the physiological context remains to be clarified.

Base Sequence↗
PubMed1995

Amino acid replacements leading to temperature-sensitive defects of the NS1 protein of influenza A virus.

The nonstructural (NS) genes of two influenza virus temperature-sensitive (ts) reassortants have been sequenced and compared with the corresponding wild type sequences. Ts 412 has a single base substitution (G100-->A) leading to an amino acid replacement (Arg 25-->Lys) in the NS1 protein. Ts 451 also has a single base substitution (U273-->C) leading to an amino acid replacement (Ser 83-->Pro) in the NS1 protein. In ts 412 infected cells at the nonpermissive temperature very little M1 and HA mRNA and proteins are synthesized, suggesting that NS1 is involved in a transcriptional regulation process. The ts mutation in ts 451 could be extragenically suppressed by replacement of the PB1 and/or PA protein genes of the mutant by the allelic genes of PR8. Both observations suggest that NS1 cooperates with the polymerase complex.

Influenza A virus↗
PubMed1995

Inhibition of the intracellular transport of influenza viral RNA by actinomycin D.

In primary chicken embryo cells infected with fowl plague virus addition of actinomycin D at defined times during the infection cycle has different consequences on viral replication. If actinomycin D is added immediately after infection with a concentration, which inhibits viral RNA synthesis only partially, it interferes with the nucleo-cytoplasmic transport of all viral RNA species (mRNA and vRNA) so far tested. If actinomycin D is present during infection (adsorption, penetration and uncoating) no viral RNA is synthesized, and the nucleocapsid of the infecting virus does not reach the nucleus, as shown by fluorescent antibodies. Therefore the primary effect of actinomycin D on influenza virus replication is on the transport of the incoming vRNPs from the cytoplasm to the cell nucleus, which is the cell compartment where transcription takes place.

Animals↗
PubMed1995

Diagnosis of ornithosis by cell culture and polymerase chain reaction in a patient with chronic pneumonia.

We report the case of a woman who had pneumonia due to Chlamydia psittaci. A Chlamydia species was determined to be the causative agent of the pneumonia because it was isolated from bronchoalveolar lavage fluid, because it could be detected in lung biopsy specimens by the direct immunofluorescence technique, and because Chlamydia-specific antibodies could be detected by ELISA and microimmunofluorescence. The infectious agent could not be identified at the species level with use of serological techniques, but the isolate was determined to be C. psittaci by PCR with use of species- and genus-specific sequences within the chlamydial lipopolysaccharide biosynthesis gene gseA. The case reported herein exemplifies the problems encountered in diagnosing ornithosis and shows that isolation of the etiologic agent followed by identification of the species by PCR is helpful in diagnosing this rare disease. In addition, the findings in our case show that laboratory personnel who are conducting tests for Chlamydia pneumoniae should be aware of the risk of accidentally isolating highly infectious C. psittaci organisms.

Aged↗
PubMed1994

Effects of guanosine 3',5'-bisdiphosphate (ppGpp) on rate of transcription elongation in isoleucine-starved Escherichia coli.

We measured the transcription elongation rate on two mRNA genes, i.e. infB and lacZ, and on a part of the rrnB gene under conditions when wild type (rel+) Escherichia coli and relaxed (relA) mutants were exposed to isoleucine starvation. The RNA chain growth rates were calculated from the time lag between induction of transcription and the appearance of specific hybridization to probes complementary to the 3' ends of the genes, i.e. from the transcription time. The rate of mRNA chain elongation responded differently in rel+ and relA strains exposed to isoleucine starvation as it decreased (approximately 50%) in rel+ strains that accumulated high concentrations of guanosine 3',5'-bisdiphosphate (ppGpp) and increased (approximately 15%) the relA mutant whose ppGpp pool decayed during starvation. These results show that ppGpp inhibits mRNA chain elongation in vivo. However, stable RNA chain elongation appeared unaffected by ppGpp pool size and was twice as fast as mRNA chain elongation in exponentially growing cells.

Base Sequence↗
PubMed1994

IFP 35 is an interferon-induced leucine zipper protein that undergoes interferon-regulated cellular redistribution.

We have isolated a new human cDNA, named IFP 35, whose expression is regulated by interferons (IFN). Induction of IFP 35 mRNA in HeLa cells by IFN is due, at least in part, to increased transcription. In response to IFN treatment, the expression of IFP 35 mRNA is seen in a wide range of different cell types, including fibroblasts, macrophages, and epithelial cells. The cDNA sequence encodes a 282-amino acid protein with a deduced molecular mass of 31,130 Da. In vitro translation of mRNA obtained by both in vitro transcription and hybrid selection resulted in the synthesis of a 35-kDa protein. Antisera raised against IFP 35 recognized a protein with an apparent molecular mass of 35 kDa in HeLa cells. Amino acid sequence analysis revealed a leucine zipper motif in an alpha-helical configuration at the extreme amino terminus of IFP 35. Notable IFP 35 is a unique novel leucine zipper protein in that it lacks a basic domain critical for DNA binding. IFP 35 can specifically form homodimers in vitro. Western blot analysis of fractionated cell extracts indicates increased nuclear localization following IFN treatment.

Amino Acid Sequence↗
PubMed1994

Influenza A virus late mRNAs are specifically retained in the nucleus in the presence of a methyltransferase or a protein kinase inhibitor.

The synthesis of influenza A virus RNA and proteins represents a highly regulated process whereby variable amounts of early and late viral RNAs and proteins may be produced. This regulation is upset by the presence of the methyltransferase inhibitor 3-deazaadenosine (3DA-Ado) or the protein kinase inhibitor H7, resulting in complete or partial inhibition of synthesis of late proteins but normal production of early proteins. Although the total yield of viral mRNAs is somewhat reduced by treatment with 3DA-Ado, the mRNAs that are produced can still be translated in vitro. Both 3DA-Ado and H7 interfere specifically with the transport of the late viral mRNAs from the nucleus to the cytoplasm, but do not affect transport of early mRNA. From these results we conclude that during influenza virus replication, posttranscriptional regulation takes place on the level of mRNA transport. Since hemagglutinin mRNA migrates to the cytoplasm in the presence of 3DA-Ado plus cycloheximide, we assume that a viral protein is involved in the regulation mechanism.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Desferrioxamine-promoted virulence of Yersinia enterocolitica in mice depends on both desferrioxamine type and mouse strain.

The effects of desferrioxamine B (DFOB) and G (DFOG) on growth promotion and virulence of Yersinia enterocolitica as well as on T cell activation and proliferation were investigated. Both desferrioxamines promoted growth of Y. enterocolitica O:8 (WA-314) and O:3 (Y-108). DFOB had a greater immunosuppressive effect on T cells than did DFOG. These results suggest a dual role of DFOB in yersiniosis: growth promotion of the pathogen and immunosuppression of the host. The LD50 of both Yersinia strains for mice was reduced by DFOB but not by DFOG. However, the LD50 of yersiniae was reduced by DFOB to a greater extent in Yersinia-resistant C57BL/6 than in Yersinia-susceptible BALB/c mice. The different impact of DFOB on the LD50 of Y. enterocolitica in C57BL/6 and BALB/c mice might be due to an immunomodulating effect of DFOB.

Animals↗
PubMed1994

Genetic alterations in streptomycin-resistant Mycobacterium tuberculosis: mapping of mutations conferring resistance.

We report on the identification of mutations associated with streptomycin resistance in Mycobacterium tuberculosis. Two isolates (3656 and 3976) showed a wild-type ribosomal protein, S12, but exhibited a single point mutation at 16S rRNA position 491 (C-->T) or 512 (C-->T), respectively. Sequence analysis of a third isolate (2438) revealed a single base change at 16S rRNA position 904 (A-->G). This position is equivalent to invariant position 913 of the Escherichia coli 16S rRNA gene, an A-->G transition of which has been shown previously to impair streptomycin binding and streptomycin-induced misreading in vivo. Surprisingly, strain 2438 harbors an additional mutation in the ribosomal protein S12 (Lys-88-->Gln).

Base Sequence↗
PubMed1994

The RNA chain elongation rate in Escherichia coli depends on the growth rate.

We determined the rates of mRNA and protein chain elongation on the lacZ gene during exponential growth on different carbon sources. The RNA chain elongation rate was calculated from measurements of the time elapsing between induction of lacZ expression and detection of specific hybridization with a probe near the 3' end of the mRNA. The elongation rate for the transcripts decreased 40% when the growth rate decreased by a factor of 4, and it always correlated with the rate of translation elongation. A similar growth rate dependency was seen for transcription on the infB gene and on a part of the rrnB gene fused to a synthetic, inducible promoter. However, the untranslated RNA chain specified by the rrnB gene was elongated nearly twice as fast as the two mRNA species encoded by infB and lacZ.

Cell Division↗