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Biomedical subjects

K C Winkler

Publications and source records attributed to K C Winkler.

At least 19 recordsLinked to original sources
PubMed1982

[Recombinant DNA and genetic manipulation, reality and fantasy (author's transl)].

Genetic manipulation deliberately tries to influence the progeny of a living organism to achieve a human purpose. Well-known instances are artificial insemination and embryo transfer. The species barrier is not broken in this procedure and a surrogate mother is required in every case. In frogs, the nuclei og a number of fertilized ova may be replaced by the nuclei of vegetative cells of a single frog (a) and thus produce a clone of identical frogs (a). This is impossible in mammals. Parts of plants and even cultures of vegetative plant cells may develop into complete plants. This fact is gratefully used for the rapid propagation of useful hybrids. The recombinant DNA procedure is a method by which particles of any DNA can be multiplied in a culture of bacteria. This DNA can consequently be cloned. The basic principles of the procedure are discussed. When the recombinant DNA technique is used, the species barrier is passed. It can only be used, however, to influence the heritable characteristics of unicellular organisms or vegetative cells in cultures. This may possibly include plants. The risks run by the investigator using this technique are much smaller than those to which he is exposed in the case of pathogenic bacteria. When non-pathogenic bacteria showing a high degree of biological containment are used, the hazard of spreading in the environment is small. This problem undoubtedly merits further attention in other organisms. Mammals cannot be 'clonized' or freaks produced using recombinant DNA procedures.

Animals↗
PubMed1981

Resistance transfer in mixed cultures of Staphylococcus aureus.

Transfer of resistance markers was regularly observed in mixed cultures of pairs of constructed strains of Staphylococcus aureus. This transfer was shown to be due to general transduction and required a lysogenic donor strain, carrying a transducing phage of serotype B and a transducible plasmid, and an acceptor strain without either strong restriction or an incompatible plasmid. Transfer was sometimes bidirectional when both strains carried a transducing phage. Unidirectional transfer occurred when the acceptor strain was immune. When the acceptor was sensitive to the donor phage, reversed transfer of a marker from the acceptor to the donor could take place. The kinetics of transfer are governed by the rate of phage production, the rate of phage adsorption and the frequency of transduction. A mathematical model has been developed to describe the interplay of these factors. The numbers of transductants observed in mixed cultures agreed with those expected from the model. Transfer was also observed in mixed cultures of constructed strains and wild-type strains. Transfer between wild-type strains is also possible, but was not observed in many combinations because of lack of transducing phage, strong restriction or other factors. Transfer was also observed in local lesions in mice infected with two strains and in mixtures inoculated on to human skin.

Animals↗
PubMed1980

Epidemiology of mumps in the Netherlands.

In a Dutch population group neutralizing antibodies against mumps virus were determined by a plaque reduction technique, which proved reproducible, sensitive and specific. The results with sera of about 800 suburban children show that mumps is acquired at an early age with peak acquisition rates between the ages of four and six years. Over 90% have acquired mumps before the age of 14 years. More than 95% of about 1000 adults (18--65 years) have neutralizing antibodies. The relatively constant median titre suggests that antibodies persist during life. During a family study 77 clinical and 18 subclinical cases were observed. In families with index cases the attack rate was 26/37 = 0.71. Eleven children (excluding six babies) escaped infection. The mean attack rate during the epidemic was 0.30. The mean titre of mumps neutralizing antibody is maximal during the first year after the disease but declines during childhood. Mothers exposed to mumps in the family occasionally showed a significant rise in titre. Some seronegative mothers remained seronegative after exposure.

Adolescent↗
PubMed1979

Restriction of resistance transfer in Staphylococcus aureus.

The transduction frequency of wild type resistance plasmids carrying the modification of a defined donor strain into a series of acceptor strains with different restriction systems and into restriction-deficient mutants was studied. Plasmids carrying resistance to tetracycline, chloramphenicol and penicillin were in general as sensitive as the transducing phage to restriction and modification. Plasmids carrying penicillinase of type A and C could be transferred into strains of group II.

Chloramphenicol↗
PubMed1977

Restriction-deficient mutants of Staphylococcus aureus.

A series of restriction-deficient mutants was isolated from non-lysogenic strains of Staphylococcus aureus belonging to phage groups I and II. Some mutants were sensitive to all phages tested. With one possible exception, all the mutants were unaffected in their modification systems. The breakdown of DNA of phages, restricted in the parental strains, was reduced in both the mutants that were tested. The restriction in propagating strain 3A could be transduced to its restriction-deficient mutant. The transduction efficiency increased after ultraviolet irradiation of the transducing phage suggesting that the gene for restriction is present on the bacterial chromosome.

DNA Restriction Enzymes↗
PubMed1975

The faecal flora in ulcerative colitis.

Differential counts of the faecal flora of patients with ulcerative colitis showed a dysbiotic flora with a 100-fold increase of group-D streptococci and a reduction of bifidobacteria in comparison with the stable eubiotic flora of healthy subjects. The increase in number in group-D streptococci was accompanied by an increase in variety. About four different varieties of enterococci were found in faeces from patients compared with one or two in samples from healthy subjects. The strains isolated from patients were more active in mucin breakdown, and only strains from patients were able to break down hyaluronic acid. Lactic acid could be formed from these substrates. The increased secretion of mucin in colitis and the presence of unprotected hyaluronic acid in ulcers seem to select these organisms which are probably the cause of the high lactic-acid content of the faeces in such patients.

Actinomycetaceae↗
PubMed1974

Inactivation of encephalomyocarditis virus in aerosols: fate of virus protein and ribonucleic acid.

After aerosolization at relative humidities of 50% or lower, encephalomyocarditis virus is rapidly inactivated. In this process the protein coat of the virion is damaged. This appears as a loss of hemagglutination activity and loss of affinity for hemagglutination inhibiting antibodies. The ribonucleic acid of the virus retains its infectivity but it becomes susceptible to ribonuclease. It sediments in sucrose gradients when centrifuged at high speed with the same velocity as free infectious ribonucleic acid extracted with phenol from intact encephalomyocarditis virus.

Aerosols↗
PubMed1970

Selective medium for Moraxella nonliquefaciens.

A medium is described which selectively inhibits most bacteria from the normal flora of the conjunctiva, the lid-margin, and the upper respiratory tract but permits growth of Moraxella nonliquefaciens, M. liquefaciens, and the less fastidious strains of M. lacunata. The selective conditions are obtained with thiostrepton, tyrothricin, and sodium nalidixinate as inhibitors. Incubation under increased CO(2) pressure increased the number of primary isolations. M. nonliquefaciens was isolated on the selective medium twice as many times as on other media.

Anti-Bacterial Agents↗