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Biomedical subjects

H Kollaritsch

Publications and source records attributed to H Kollaritsch.

66 records · Page 4Linked to original sources
PubMed1984

Risks and benefits of vaccinations.

Any medical intervention is expected to prevent sickness and complications of a disease rather than to induce them. This is true for therapy as well as prophylaxis. Special formulas have been developed to calculate the risks and benefits of vaccinations simply but with sufficient accuracy. The risk ratio (Q) tells how many times the risk of contracting certain complications or even death from a disease is greater in unvaccinated than in vaccinated individuals. The risk difference (D) directly expresses the number of complications or deaths that may be prevented by a certain vaccination. It is even possible to evaluate the epidemiologic trend of a disease and to calculate or estimate the point of time when the risks of disease and vaccination are just balanced, ie, when a vaccination has lost its beneficial effect. Vaccinations against measles, poliomyelitis and tick borne encephalitis in Austria are highly beneficial. BCG vaccination is still beneficial on a low level in Austria as far as protection against tuberculosis is concerned. This effect will persist for the rest of this century. The benefit of pertussis vaccination depends on the local epidemiologic situation. It has expired for non-risk groups in Austria since 1976 but continues to persist in the US.

Austria↗
PubMed1984

[Entamoeba histolytica: II. Effect of humoral immune mechanisms on cytotoxic activity].

The time dependency of the cytotoxic action of E. histolytica against tissue culture cells of mammalian origin was assessed in a 51Cr-release assay. Obviously, the amebae-dependent cytotoxic activity within the first 30-60 min of the assay against K562 (an erythroleukemic cell line) and MH1C1 (a rat hepatoma cell line) correlated with the pathogenicity of the respective amebae in vivo as measured by the hamster liver infectivity test. The in vivo apathogenic strain of E. histolytica (HK9) exhibited a delayed cytotoxic action in comparison with the in vivo pathogenic strain (SFL3), which revealed approximately 50% of maximum 51Cr-release after 10 min of the assay. Peripheral blood lymphocytes and HeLa cells proved to be not suitable to discriminate between pathogenic and apathogenic strains in vitro. Human antibodies directed against E. histolytica were capable of inhibiting the cytotoxic action of pathogenic amebae against K562 and MH1C1 within the first 30-60 min of the assay, revealing a kinetic pattern nearly identical with that observed with apathogenic amebae against K562. Possibly, this antibody-mediated inhibition of the cytotoxic action of E. histolytica against target cells reflects one of the defence mechanisms of the host against invasive amebiasis.

Animals↗
PubMed1983

[Entamoeba histolytica: I. Mechanism of cytotoxic activity].

Cytotoxic action against K562-tissue culture cells was investigated under various conditions with a Chromium-release-assay. When amoebae and target cells were centrifuged together, pathogenic strains of amoebae induced a very fast increase of target cell lysis (up to 50% of maximum lysis after 10 minutes). Only a minor degree of target cell lysis resulted, however, when amoebae and K562 cells were kept in suspension. When amoebae were eliminated selectively by addition of complement 10 minutes after starting the experiment, this fast increase of lysis could not be prevented. These observations suggest that the cytotoxic action might take place in two distinct phases. The first step ("lethal hit") seems to be temperature-independent, whereas a temperature of 37 degrees C is necessary for the second step to occur during which cytoplasmic material is released (chromium release). The presence of amoebae is not necessary for the second step. When amoebae together with and target cells are kept in suspension, amoebae lost their capability of setting the "lethal hit" with increasing time of coincubation. It seems, as if the "lethal hit" cannot be accomplished effectively under the conditions of suspension: cytotoxic substances released by the amoebae cannot be transferred to the target cells and are lost in the fluid phase. Thereby, the amoebae are depleted of such substances. Thus, a stable contact between amoebae and target cells for at least a few minutes seems to be necessary for the expression of cytotoxicity.

Amebiasis↗
PubMedDate not supplied

Plasmodium falciparum: susceptibility in vitro and in vivo to chloroquine and sulfadoxine-pyrimethamine in Ghanaian schoolchildren.

In Ghana, resistance of Plasmodium falciparum to chloroquine was observed for the first time in 1986. By the end of 1991 it had reached a high frequency and a substantial degree. A combined study in vivo and in vitro of the response of P. falciparum to chloroquine and sulfadoxine/pyrimethamine was carried out in Madina, Accra, in the coastal area of Ghana, late in 1991. 96 valid tests in vivo were performed with children and adolescents. There were 52 successful tests in vitro with chloroquine, and 52 with sulfadoxine/pyrimethamine. 45% of the chloroquine tests in vivo and 37% of the sulfadoxine/pyrimethamine tests in vivo indicated RII/RIII resistance. Results in vivo and in vitro were significantly correlated. The presence of RIII responses, 9% with chloroquine and 14% with sulfadoxine/pyrimethamine, indicates a need for third-line antimalarial drugs, the unregulated use of which may entail the risk of early and rapid occurrence of multi-resistance.

Adolescent↗
PubMedDate not supplied

Chloroquine resistance of Plasmodium falciparum: a biological advantage?

The response in vitro of Plasmodium falciparum to chloroquine, mefloquine and quinine was studied in a hyperendemic peri-urban area of Accra, Ghana, during the fourth quarter of 1991, yielding a total of 159 valid tests. Schizont maturation in drug-free controls and effective chloroquine concentrations were strongly correlated. This was not seen with mefloquine or quinine. Higher mean parasitaemia in untreated oligo-symptomatic carriers of overtly chloroquine-resistant P. falciparum than in carriers of more sensitive parasites was another indication of higher viability and biological advantage of chloroquine-resistant P. falciparum that may conceivably have clinical implications.

Adolescent↗