PubMed Health⌕ Search

Biomedical subjects

M Hensel

Publications and source records attributed to M Hensel.

71 records · Page 4Linked to original sources
PubMed1995

Endothelial damage induced by nitric oxide: synergism with reactive oxygen species.

Interactions of reactive oxygen and nitrogen species to mediate endothelial cell damage were studied in vitro. S-Nitroso-N-acetyl-DL-penicillamine (SNAP), 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1) and sodiumnitroprusside (SNP) were used as NO.-donating agents. The toxicity of SIN-1 (5 mM), which produces both O2-. and NO., was reduced when catalase was added to remove H2O2 whereas superoxide dismutase had a marginal protective influence. Low doses of H2O2 producing enzymes added to low doses of SNAP (1 mM) or SNP (5 mM) substantially increased toxicity. Such damage was absent when catalase was present, but was still seen in the presence of superoxide dismutase. Non toxic doses of KCN (1 mM), antimycin A (1 microM), and rotenone (0.5 microM) in order to increase endogeneously produced reactive oxygen species increased toxic effects by 20-30% (p < 0.05). In our experiments we provide evidence that extracellularly produced H2O2 rather than O2-. enhances toxicity of NO. against endothelial cells. Likewise, endogeneous production of reactive oxygen species may increase toxicity of NO..

Analysis of Variance↗
PubMed1995

Simultaneous identification of bacterial virulence genes by negative selection.

An insertional mutagenesis system that uses transposons carrying unique DNA sequence tags was developed for the isolation of bacterial virulence genes. The tags from a mixed population of bacterial mutants representing the inoculum and bacteria recovered from infected hosts were detected by amplification, radiolabeling, and hybridization analysis. When applied to a murine model of typhoid fever caused by Salmonella typhimurium, mutants with attenuated virulence were revealed by use of tags that were present in the inoculum but not in bacteria recovered from infected mice. This approach resulted in the identification of new virulence genes, some of which are related to, but functionally distinct from, the inv/spa family of S. typhimurium.

Animals↗
PubMed1995

The ATP synthase (F1F0) of Streptomyces lividans: sequencing of the atp operon and phylogenetic considerations with subunit beta.

The DNA encoding the subunits of the ATP synthase (F1F0) of Streptomyces lividans 66 strain 1326 was identified using oligodeoxyribonucleotide probes derived from the N-terminal sequence of subunit gamma of the F1 complex. The complete nucleotide sequence of the operon was determined. The atp operon contains nine genes, atpIBEFHAGDC, encoding the eight structural components of the ATP synthase complex and the i protein, a polypeptide of unknown function. The gene order found is identical to that in other non-photosynthetic eubacteria. The determination of the N-terminal amino acid (aa) sequences of the F1 subunits alpha, beta, gamma, delta and epsilon allowed us to identify the translational start points and to define the primary structures of the proteins. The aa sequence deduced for subunit delta revealed an N-terminal extension of about 90 aa, which is not present in any delta subunit or OSCP (oligomycin sensitivity-conferral protein) of other species studied so far. The phylogenetic relationship of eu- and archaebacteria was investigated using sequencing data of the highly conserved beta subunit of different ATP synthases including that of S. lividans. The calculations revealed that S. lividans beta does not form a phylogenetic group together with the Gram+ taxa of low G+C contents, but is more closely related to the beta subunit of Rhodobacteria.

Amino Acid Sequence↗
PubMed1994

Association between cervical inflammation and cervical shedding of human immunodeficiency virus DNA.

A cross-sectional study was conducted among prostitutes in Nairobi, Kenya, to determine the prevalence and correlates of cervical human immunodeficiency virus (HIV) DNA. Ninety-two HIV-seropositive prostitutes were evaluated during 137 clinic visits. Cervical HIV DNA was detected by polymerase chain reaction assay in 36 (39%) women at initial visits and in 40 (44%) women at any visit. There was a significant correlation between cervical HIV and microscopic evidence of cervical inflammation (odds ratio [OR], 7.2; 95% confidence interval [CI], 2.1-24.6). Using multivariate analysis to adjust for possible confounding, the adjusted OR for the association between cervical inflammation and cervical HIV DNA was 8.7 (95% CI, 2.0-37.2). Conditions associated with cervical inflammation are associated with the detection of HIV proviral DNA. Whether such conditions lead to increased infectivity remains to be proven.

Adult↗
PubMed1993

Detection of HIV DNA in cervical and vaginal secretions. Prevalence and correlates among women in Nairobi, Kenya.

OBJECTIVE: Factors that influence heterosexual transmission of the human immunodeficiency virus (HIV), including sexually transmitted diseases, contraceptive practices, sexual practices, HIV-related immunosuppression, and presence of cervical ectopy and the penile foreskin, have been identified through cross-sectional and prospective cohort epidemiological studies. To more directly characterize factors that influence infectivity, we conducted a study of HIV shedding from the genital tract in women. DESIGN: Ninety-seven HIV-seropositive women attending a sexually transmitted disease clinic in Nairobi, Kenya, completed a questionnaire and underwent a physical examination and an evaluation for sexually transmitted diseases. Cervical and vaginal secretions were obtained for HIV DNA detection using polymerase chain reaction amplification. RESULTS: Human immunodeficiency virus DNA was detected by polymerase chain reaction in 28 (33%) of 84 cervical samples and 13 (17%) of 77 vaginal samples. The prevalence of HIV was higher in specimens from the endocervix than from the vaginal wall (P = .002), and there was no correlation between presence of virus at the two sites. After adjusting for age, cervical HIV shedding was independently associated with oral contraceptive pill use (odds ratio [OR], 11.6; 95% confidence interval [CI], 1.7 to 77.6), cervical mucopus (OR, 6.2; 95% CI, 0.9 to 41.4; P = .05), cervical ectopy (OR, 5.0; 95% CI, 1.5 to 16.9), and pregnancy (OR, 4.5; 95% CI, 1.2 to 16.3). CONCLUSIONS: Human immunodeficiency virus was detected in one third of cervical samples and one sixth of vaginal samples. The presence of HIV DNA in cervical secretions was significantly associated with oral contraceptive pill use, cervical ectopy, and pregnancy. There was a marginally significant association with cervical mucopus. The identification of factors that increase the infectivity of women suggests potential strategies for reducing heterosexual transmission of HIV.

AIDS Serodiagnosis↗
PubMed1993

Human immunodeficiency virus infection among high-risk seronegative prostitutes in Nairobi.

To determine the frequency and duration of antibody-negative human immunodeficiency virus (HIV) infection among heterosexually exposed African women, 56 HIV-seronegative female prostitutes in Nairobi were studied. Polymerase chain reaction (PCR) was used to detect HIV DNA in peripheral blood at enrollment, and women were followed prospectively with serologic testing to determine HIV seroincidence. Six women (11%) were infected with HIV by PCR criteria at enrollment. Seroconversion occurred in 5 of these subjects within 1-12 months, while the sixth remained seronegative when last evaluated at 5 months. The cumulative annual seroconversion rate in the entire cohort was 38%. Using maximum likelihood analysis, the mean interval between HIV infection and seroconversion was estimated to be between 3 and 4 months, similar to that described for homosexual men and blood product recipients in the United States. Prolonged HIV infection in the absence of antibodies appears to be uncommon in this setting.

Adult↗
PubMed1992

Human immunodeficiency virus infection of cells arrested in the cell cycle.

Cell proliferation is necessary for proviral integration and productive infection of most retroviruses. Nevertheless, the human immunodeficiency virus (HIV) can infect non-dividing macrophages. This ability to grow in non-dividing cells is not specific to macrophages because, as we show here, CD4+ HeLa cells arrested at stage G2 of the cell cycle can be infected by HIV-1. Proliferation is necessary for these same cells to be infected by a murine retrovirus, MuLV. HIV-1 integrates into the arrested cell DNA and produces viral RNA and protein in a pattern similar to that in normal cells. In addition, our data suggest that the ability to infect non-dividing cells is due to one of the HIV-1 core virion proteins. HIV infection of non-dividing cells distinguishes lentiviruses from other retroviruses and is likely to be important in the natural history of HIV infection.

Base Sequence↗
PubMed1992

[The HELLP syndrome--a challenge to the obstetrician and the intensive care therapist].

The HELLP-syndrome is a severe complication in late pregnancy. The etiology is still largely unknown. It is defined as a separate disease but also as a severe course of EHP-gestosis. It is mainly characterised by increased liver enzymes, a low platelet count, increased haemolysis and hypertension. According to primary organ affection, neurological symptoms and acute respiratory distress syndrome, acute renal insufficiency and/or upper abdominal complaints may occur. The only causal therapy is immediate caesarean section. Postoperative intensive care must be guaranteed. As a gentle anaesthetic method neuroleptanalgesia is recommended. Based on 7 of our own case reports, pathophysiology and therapy are discussed.

Adult↗
PubMed1991

Purification and characterization of the F1 portion of the ATP synthase (F1Fo) of Streptomyces lividans.

The F1 complex of the ATP synthase of Streptomyces lividans was isolated and purified. The procedure involved the solubilization of F1 from membranes with buffer of low ionic strength in the presence of EDTA, ion-exchange chromatography and gel filtration. The purified F1 complex from S. lividans (SLF1) consists of five subunits alpha, beta, gamma, delta and epsilon with molecular masses of 58,000, 50,000, 36,000, 28,000 and 13,000, respectively and exhibits immunological cross-reactivity with the F1 portion purified from Escherichia coli (ECF1). The enzymatic properties of SLF1 were determined by the use of microtiter-plate-based assay and compared with data obtained for ECF1. ATPase activity of SLF1 (specific activity: 20-30 U/mg) was only observed in the presence of high concentrations of Ca2+ (10mM). Stimulation of the ATPase activity by Mg2+ was not detectable; quite to the contrary, Mg2+ inhibited the Ca(2+)-stimulated activity of SLF1. SLF1 was re-bound to F1-stripped membranes of S. lividans, but not to F1-stripped membrane vesicles of E. coli. In contrast, ECF1 could be cross-reconstituted with F1-stripped membranes of S. lividans; however, a structural but not a functional reconstitution of the hybrid F1Fo complex was observed.

Cell Membrane↗
PubMed1991

[Preoperative hemodilution as a possibility in autologous blood transfusion. A report of experiences].

The various methods of autologous blood donation are gaining importance in clinical practice. Acute preoperative isovolaemic haemodilution represents a cost-cutting and readily practicable option. It is a method that brings positive haemodynamic effects and improves the blood's flowing properties by lowering its viscosity and raising cardiac output, as well as avoiding the dangers associated with foreign blood transfusion. Risks to the patient can largely be eliminated by keeping an eye out for contra-indications and ensuring careful perioperative monitoring. The successful use of this method depends on a clear organizational concept and close collaboration between surgeons, anaesthesists and transfusions specialists.

Blood Loss, Surgical↗
PubMed1990

Orientation of subunit c of the ATP synthase of Escherichia coli--a study with peptide-specific antibodies.

Antibodies were raised against a peptide of subunit c of the ATP synthase from Escherichia coli obtained by cleavage with cyanogen bromide. This peptide comprises the amino acid residues Gly-18 to Met-57 and contains the highly conserved, hydrophilic stretch of subunit c. Several conformation-specific populations of antibodies recognized this region both in isolated subunit c and in the intact F0 complex. In antibody binding studies with membrane vesicles of different orientations, recognition occurred only after incubation with everted membrane vesicles, independent of the presence or absence of F1, although a higher membrane protein concentration was necessary to observe the same antibody binding in the presence of the F1 part. From these results we conclude that the hydrophilic region of subunit c is exposed to the cytoplasmic side of the membrane.

Escherichia coli↗
PubMedDate not supplied

Regulation of virulence genes by environmental signals in Salmonella typhimurium.

Sensing and responding to environmental signals is a crucial element of bacterial pathogenicity. For a successful progression of infection, virulence gene expression is coordinated in response to habitat-specific environmental signals from the host organism. We are interested in identifying environmental cues affecting the expression of genes within Salmonella Pathogenicity Island 2 (SPI2), a virulence locus important for systemic infections by S. typhimurium. We describe our approach starting with the identification of new virulence genes, and analysis of the regulation of these genes by environmental signals leading to the proteome analysis in order to define the SPI2 regulon.

Bacterial Proteins↗
PubMedDate not supplied

[Meningitis in 154 children of a pediatric clinic in Germany: clinical and epidemiologic aspects].

In a retrospective study, the histories of the non-neonates treated for primary meningitis in the Pediatric Department of Mainz University Hospital between 1986 and 1989 were analyzed with regard to etiological, diagnostic, clinical and epidemiological criteria. In the period studied there were 37 cases of infectious meningitis (11 Neisseria meningitidis (29.7%), 7 H. influenzae (18.9%), 3 S. pneumoniae (8.1%), 16 other (43.2%)), and 117 cases of acute aseptic meningitis syndrome (12 mumps virus (10.3%), 3 Borrelia burgdorferi (7.7%), 3 FSME (2.6%), 2 herpes simplex virus, 91 other (77.8%)). Sixty-six percent of the patients were male. Of the infants with infectious meningitis, 68% were under 5 years old. In contrast, 69% of the children with noninfectious meningitis were aged 5 or older. While 70% of the infectious meningitis cases occurred in fall and winter, 64% of the cases of acute aseptic meningitis syndrome occurred in spring and summer. In differential diagnosis between infectious and acute aseptic meningitis syndrome maximal sensitivity was a CRP value exceeding 0.5 mg/dl, a CSF lactate value of over 3 mmol/l and a CSF cell count of over 2000/3 cells. In none of the cases did a second or third lumbar puncture furnish information additional to that which could have been deduced from physical examination and course of temperature. A second lumbar puncture failed to produce unexpected results, or have consequences for therapy, in any of the 14 cases with noninfectious meningitis. Of 37 infants with infectious disease, one (2.7%) died from the sequelae of pneumococcal meningitis. Recovery was partial in 8 (22.2%) of the 36 surviving infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

The influence of cellular hypoxia and reactive oxygen species on the development of endothelial cell edema.

We investigated in vitro whether endothelial cell edema is induced by cellular hypoxia or oxygen radical formation. Measurements of relative cell volume (RCV) were made using microweight analysis, liquid scintillation spectrometry and analysis of cellular protein content. To validate this method of determining cell volume, endothelial cells were incubated in media of different osmolarities. Vascular endothelial cells reacted to osmotic stress with a volume increase or decrease. The addition of xanthine oxidase (XOD; 3 mU/ml) and hypoxanthine (1 mM) for the enzymatic production of O2- caused a reproducible and significant increase in RCV by 29 +/- 8% (from 5.5 to 7.1 microliters/10(6) cells; p < 0.001) after an incubation time of 60 min. Nonenzymatically produced H2O2 (100 microM) caused a similar increase in RCV by 35 +/- 5% (from 5.5 to 7.6 microliters/10(6) cells; p < 0.001) over the same incubation period. The addition of catalase (50 U/ml) diminished the increasing effect of XOD as well as that of H2O2 on cell volume. As assessed by the uptake of the vital dye trypan blue and the release of lactate dehydrogenase into the medium, there was no significant loss of viability during the incubation time. Lower concentrations of H2O2 as well as lower activities of XOD did not induce a significant increase in RCV. Higher H2O2 concentrations and increased XOD activities caused a considerable time- and concentration-dependent injury of endothelial cells. RCV was unchanged even after long exposure (5 h) to two different hypoxic gas mixtures (3% O2:5% CO2:92% N2; 0% O2:5% CO2:95% N2). Cell viability was not impaired under hypoxic conditions. The results suggest that reactive oxygen species play a more important role in the development of endothelial cell edema than cellular hypoxia.

Animals↗