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Biomedical subjects

R Laufs

Publications and source records attributed to R Laufs.

At least 145 records · Page 8Linked to original sources
PubMed1986

[Properties and transmission of the AIDS virus].

The acquired immunodeficiency syndrome (AIDS) is caused by a retrovirus. LAV/HTLV-III is mainly transmitted by blood and sperm. More than 90% of the newly infected persons belong to four risk groups: male homosexuals, drug addicts, persons with multiple changing sex partners, and bisexuals. Infected individuals carry the virus and antiviral antibodies simultaneously in their blood. The antibodies can be demonstrated by the ELISA and immunofluorescence tests, but positive and questionable test results must be confirmed by the immunoblot. Not all of the persons carrying the virus will develop clinical symptoms, but the percentage of those suffering from severe illnesses rises with time and reaches 40% after 8 years. At present, there is no effective therapy and no vaccine will be ready in the near future. Therefore, it is necessary to take all precautions possible to prevent new infections.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Evidence for limited humoral immunoglobulin M antibody response to hepatitis B core antigen during acute and chronic hepatitis B virus infections.

The periods of persisting immunoglobulin M class antibodies to hepatitis B core antigen in 28 patients with acute hepatitis B infections and in 134 patients with chronic hepatitis B infections were studied by using an enzyme-linked immunosorbent assay and an indirect immunofluorescence technique. We showed that the clearance of antibodies to hepatitis B core antigen is independent of the degree of viremia in both forms of hepatitis.

Chronic Disease↗
PubMed1985

Double immunofluorescence microscopic technique for accurate differentiation of extracellularly and intracellularly located bacteria in cell culture.

A double immunofluorescence staining technique is described for differentiation between cell-attached (extracellular) and ingested (intracellular) bacteria by HEp-2 cells in cell culture monolayers. This method is based upon the observation that membranes of viable mammalian cells are impermeable for antibodies but are rendered permeable by treatment with fixatives. Consequently, extracellular bacteria can be stained by specific rhodamine-labeled antibodies before fixation, and intracellular bacteria can be visualized by treatment with specific fluorescein-labeled antibodies after fixation. The accuracy and simplicity of this method is demonstrated with HEp-2 cell culture monolayers as target cells and an isogenic pair of Yersinia enterocolitica, one of which is phagocytosis resistant and the other of which is phagocytosis sensitive. Furthermore, it is shown that this staining technique is also applicable for studying the interaction of bacteria with macrophages and fibroblasts.

Animals↗
PubMed1985

[Course of antibody titer following preventive hepatitis B vaccination and a recommendation for renewal following the use of H-B-Vax vaccines].

97% of the vaccinees developed anti-HBs independently of the applied vaccine (experimental vaccine or H-B-Vax). With the experimental vaccine the mean antibody titre was 1095 IMU/ml four weeks after third inoculation. Follow up revealed that during a period of 18 month individual antibody titres declined continuously to approximately one tenth. Therefore the duration of protection depends on the titre of anti-HBs which was measured after the third immunization. A control of the antibody titres should be performed after about 3-5 years, when the antibody titres are greater than 1000 IMU/ml 4 weeks after vaccination. But a control should be made already after about 1 1/2-3 years if the antibody titres are 200-1000 IMU/ml. Antibody titres between 100 and 200 IMU/ml should be estimated about 6-18 months later and titres between 10 and 100 IMU/ml already about 3-6 months later. We recommend an immediate revaccination for persons with anti-HBs titres below 10 IMU/ml. Serological findings in hospital staff of the University in Hamburg revealed the presence of protective antibodies in 11,6% which is due to a previous hepatitis B infection. In this cases vaccination was unnecessary.

Adolescent↗
PubMed1985

[Transmissible formaldehyde resistance in Serratia marcescens].

It was possible to isolate a strain of Serratia marcescens from fresh clinical bacterial isolates which was 4-6 times more resistant against formaldehyde than other strains. It was shown that the strain harbours two plasmids with molecular sizes of 58- and 90 Mdal. It was demonstrated by conjugation-, transformation- and plasmid-curing experiments that the formaldehyderesistance is plasmid mediated and transferable to E. coli. It was shown by labelling with 14C-formaldehyde that the resistant strains bind much more formaldehyde than the sensible strains.

Disinfectants↗
PubMed1984

Hepatitis B e-antigen titres for evaluating infectivity during hepatitis B virus infection.

By means of an ELISA the level of hepatitis B e-antigen (HBeAg) titre was determined in 51 patients with acute and 123 patients with persistent hepatitis B virus (HBV) infection. We also investigated 120 sera of these patients for infectivity by detecting HBV-specific DNA polymerase (DNA-P). Additional determination of the HBeAg titre revealed that the detection of HBeAg at a dilution of at least 1:50 correlates with the detection of DNA-P in 95% of cases, while in sera with an HBeAg titre of 1:25 or less DNA-P is only detectable in up to 5% of cases. Since the detection of DNA-P indicates high infectivity, certain titres of HBeAg can be employed to differentiate three different degrees of infectivity: (1) Sera without HBeAg show no or only little infectivity; (2) sera containing HBeAg greater than or equal to 1:50 are highly infectious; (3) HBeAg titres up to 1:25 indicate a medium degree of infectivity. These three markers for different degrees of infectivity were applied to study the course of infectivity during acute and persistent forms of HBV infection. In acute hepatitis B the period for the elimination of HBeAg is independent of the HBeAg titre in the first serum sample. In all cases the elimination of HBeAg in acute hepatitis B did not exceed 4 months. Patients with persistent HBV infection and an initial HBeAg titre greater than or equal to 1:50 remained at this high degree of infectivity for at least 18-30 months in 70% of cases. Only 30% of this collective showed a decrease in infectivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Genetically manipulated virulence of Yersinia enterocolitica.

Mobilizable virulence plasmids of Yersinia enterocolitica of serotypes O:3 and O:9 were constructed by cointegration of a mobilizable vector into the virulence plasmids. The obtained cointegrates were mobilized into plasmidless Y. enterocolitica strains of serotypes O:3, O:5, O:8, and O:9. The transfer experiments revealed the existence of two different subgroups of plasmid-associated traits. (i) Animal virulence functions (mouse lethality and conjuctivitis provocation) were only transferable to plasmid-cured derivatives of virulent parent strains (serotypes O:3, O:8, and O:9), but they were not transferable to Y. enterocolitica antigen reference strains (serotypes O:3 and O:8) or to a plasmidless clinical isolate of serotype O:5. A further striking result was that a serotype O:8 strain regained the mouse lethality trait after receipt of a plasmid from a strain not lethal to mice. These results demonstrate that plasmid-mediated animal virulence functions are not uniformly expressed within Y. enterocolitica. (ii) The second subgroup of plasmid-mediated traits (calcium dependency, surface agglutinogens, HEp-2 cell adherence, and protein release) were transferable to all Y. enterocolitica recipient strains tested (serotypes O:3, O:5, O:8, and O:9 of different origin). For the first time HEp-2 cell adherence and temperature-induced release of five major protein species are described as transferable traits.

Bacterial Proteins↗
PubMed1984

[Comparative studies on the rotavirus syndrome following infection with human rotavirus of the subgroup 1 or 2].

Human rotavirus infection which heals spontaneously causes gastroenteritis in newborns and infants. 150 pediatric patients infected with rotavirus as diagnosed by ELISA suffered from diarrhoea for an average of 3 days, from vomiting for 1 day, and/or fever for 1-2 days. Nowadays this disease is known as "human rotavirus syndrome". Human rotaviruses can be divided into at least 4 serotype antigens and some 3 further subgroup antigens. The serotype antigens are only detectable biologically (e.g. by neutralization test), whereas the subgroup antigens can be demonstrated as specific proteins by a solid-phase test (ELISA). This study investigated whether an infection with human rotavirus of subgroup 1 (21%) or 2 (77%), which occur most frequently causes different degrees of severity of the rotavirus syndrome. The clinical comparison of 27 (subgroup 1) and 98 (subgroup 2) infected patients shows that the disease is not significantly different. This means that the detection of subgroup antigens 1 and 2 does not result in a different prognosis for the disease. The diagnosis of subgroup antigens after human rotavirus infection is therefore clinically important only for the detection of nosocomial infections, especially due to the rarely occurring subgroups 1 and 3.

Antigens, Viral↗
PubMed1984

[Immunoprevention of hepatitis B in children].

Perinatal transmission of hepatitis B virus does not occur before the beginning of labor. Therefore, neither an embryopathy nor a fetopathy appears to be caused by an acute or chronic HBV infection during pregnancy. There is no necessity to interrupt pregnancy for the reason of a HBV infection. Transmission of HBV infection, however, may take place during delivery. By simultaneous administration of hepatitis B immunoglobulin and the HBV vaccine to the newborn infant directly after birth, perinatal infection with HBV can be prevented. This immunization procedure leads to a rapid and efficient anti-HBs response in the newborn comparable to that of adults. Protection against HBV infection by passive immunization is sufficient until active anti-HBs antibody formation is starting. The hepatitis B vaccine consists of the purified non-infectious surface of the HB virus. Due to the physical purification and chemical inactivation of the hepatitis B surface antigen (HBsAg) from human sera, the vaccine is considered to be safe. It is not harmful and exhibits an excellent compatibility in newborn infants.

Carrier State↗
PubMed1983

Plasmids of human strains of Yersinia enterocolitica: molecular relatedness and possible importance for pathogenesis.

One-hundred fifteen strain of Yersinia enterocolitica were examined for plasmids and plasmid-mediated pathogenic properties. Human strains of serotypes O:3 and O:9 harbored plasmids of 46 and 44 megadaltons, respectively, with 90% homology of DNA sequences. The plasmid-mediated properties were calcium dependence, survival in human serum, conjunctivitis provocation in guinea pigs, and O agglutinogens. One strains of serotype O:8 harbored a 42-megadalton plasmid with 75% sequence homology with plasmids of serotypes O:3 and O:9. An additional plasmid-mediated property was lethality for white mice. Filter hybridization of restriction endonuclease-digested plasmid DNA indicated that a 5.6-megadalton fragment of the plasmid of serotype O:8 had virtually no sequence homology with plasmid DNA of serotypes O:3 and O:9 and therefore may be associated with the lethal factor for mice.

Agglutinins↗
PubMed1983

Construction of a mobilizable Yersinia enterocolitica virulence plasmid.

Virulence of Yersinia enterocolitica O:8 is associated with pO:8, a 42-megadalton plasmid. We constructed a mobilizable pO:8 derivative by successive in vitro and in vivo genetic manipulations. The in vitro constructed hybrid molecule pRK290B8-5 consisting of the mobilizable vector pRK290B and a 2.9-megadalton BamHI fragment of pO:8 was conjugally transferred to a Y. enterocolitica strain of serotype O:8 which harbored the virulence plasmid pO:8. From Yersinia transconjugants, a cointegrate was isolated which apparently formed by homologous recombination between the two component plasmids. The cointegrate was mobilized into plasmidless Y. enterocolitica strains of different serotypes. The transconjugants of serotype O:8 were found to express all four plasmid-associated phenotypes: (i) mouse lethality (Ml), (ii) conjunctivitis provocation in the guinea pig eye (Con), (iii) calcium requirement for growth at 37 degrees C (Mox), and (iv) agglutinogens (Ag8). The transconjugants of serotype O:3 expressed the phenotypes Con, Mox, and Ag8 but were nonlethal for mice (Ml-). The transconjugants of serotype O:5 remained avirulent for mice (Ml-) and for the guinea pig eye (Con-) but expressed the phenotypes Mox and Ag8. These data show that the virulence plasmid is probably not functionally interchangeable within different serotypes of Y. enterocolitica.

Conjugation, Genetic↗
PubMed1983

Amplification of resistance genes in Haemophilus influenzae plasmids.

Intramolecular amplification produces tandem repeats of tetracycline and combined tetracycline-chloramphenicol resistance determinants in conjugative plasmids of Haemophilus influenzae. This process depends on host recombination pathways. Physical mapping revealed the tetracycline transposon involved in amplification to be almost identical with Tn10, including two IS10 insertion elements. The chloramphenicol resistance determinant of the combined transposon is 1.9 kilobases (kb) in size and is bound by two 1.3-kb inverted repeats. Insertion in the close vicinity of the inside end of the left-hand IS10 generates a deletion of a 1.6-kb Tn10 region. The amplifiable units were resolved to comprise not only the respective resistance transposons, but also an additional 1.6-kb sequence (designated AS) which was demonstrated to be identically present in the different amplification systems studied. AS separates amplified transposons from each other, thereby maintaining the same orientation. Moreover, AS is present at the left flank of the transposons, but is missing at the right one. It was shown that AS represents a general constituent of the H. influenzae plasmids of the 45-kb class. Evaluation of the results suggests that AS is responsible for the recombinational events involved in the gene amplification process.

Chloramphenicol↗
PubMed1983

Circularized copies of amplifiable resistance genes from Haemophilus influenzae plasmids.

Tandem repeat amplification of resistance determinants in Haemophilus influenzae plasmids is associated with the occurrence of separate circular DNA molecules. They were demonstrated to represent mono- and multimeric forms of the amplifiable segments of the plasmids which comprise the respective resistance transposons and an additional region designated as an amplification sequence. The latter region mediates the recombinational events involved in amplification. The DNA circles apparently lack the ability to replicate autonomously but most probably provide an effective means for the translocation of resistance genes from one plasmid to another.

DNA Restriction Enzymes↗
PubMed1983

Microenzyme-linked immunosorbent assay for the detection of specific IgM antibodies in human syphilis.

An enzyme-linked immunosorbent assay (ELISA) using a highly purified soluble antigen prepared from pathogenic Treponema pallidum (Nichols) was carried out to detect specific IgM antibodies in syphilis. Serum specimens from 365 patients with untreated or treated syphilis were tested by the ELISA and by the 19S(IgM) fluorescent treponemal antibody-absorbed test. In the ELISA sera were preabsorbed with aggregated human IgG to eliminate any rheumatoid factor present. Sera from 331 healthy blood donors served as controls. The results of both tests correlated well. The specificity and sensitivity of the treponemal ELISA were both greater than 97%. The assay was easy to perform and may be automated.

Antibodies, Bacterial↗
PubMed1983

[Results of active preventive vaccination against hepatitis B with a German vaccine].

53 persons at high risk for hepatitis B infection have been vaccinated with a hepatitis B vaccine produced in the Hygiene Institute of the University of Göttingen. The vaccine proved to be without side effects in all vaccinees. Only minor complaints at the site of inoculation were registered. Three vaccinations are necessary. Protective antibodies were present in 96% of the vaccinees after the third inoculation. The female vaccinees developed anti HBs earlier than the males, moreover they showed significantly higher antibody titers. A simultaneous active and passive immunization is possible. To minimize the risk of contracting a hepatitis B or a non A- non B hepatitis as a result of the vaccination only such vaccines should be used which have been prepared from sera containing anti-HBe and which have been inactivated with a high dose of formaldehyde.

Adult↗
PubMed1981

Origin of Haemophilus influenzae R factors.

The Haemophilus influenzae R plasmids specifying resistance against one, two, or three antibiotics which have emerged in different parts of the world were shown to have closely related but not identical plasmid cores. The gene for ampicillin resistance in the H. influenzae plasmid pKRE5367 is part of a transposon similar to Tn3, which was transposed from pKRE5367 onto RSF1010 in Escherichia coli. An indigenous H. influenzae plasmid (pW266) was isolated. Its properties correspond to those of the H. influenzae R plasmids, except for the presence of a drug resistance transposon. The in vitro-generated H. influenzae R plasmids carrying an ampicillin resistance transposon, a tetracycline resistance transposon, and a transposon for combined tetracycline-chloramphenicol resistance resembled the natural isolates. The findings support the hypothesis that the R plasmids of H. influenzae are of multiclonal evolutionary origin.

Ampicillin↗
PubMed1980

[Hepatitis viruses of man: transmission, epidemiology and immunology (author's transl)].

The isolation and characterization of the hepatitis A virus (HAV) and the hepatitis B virus (HBV) resulted in great advances in the serological diagnosis and the prophylaxis. About 20% of the viral hepatitis cases are caused by the HAV. The hepatitis A never becomes chronic and can be diagnosed by the detection of HAV antibodies of the IgM type. The HBV is the etiologic agent in 60% of the hepatitis cases and 10% of these become chronic. It is possible to immunize against the HBV and to reduce the number of neonatal infections.

Antibodies, Viral↗