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Biomedical subjects

R Stumpf

Publications and source records attributed to R Stumpf.

At least 19 recordsLinked to original sources
PubMed2001

DPOAE-patterns in different types of autosomal-dominant nonsyndromal hearing impairment.

Twelve families with autosomal-dominant nonsyndromal hearing impairment (ADNSHI) were examined. The mode of inheritance was determined by pedigree and at least three generations with affected persons had to be found. Pure tone audiogram (PTA), DP-gram and caloric vestibular test (CVT) were performed on 30 affected persons. By PTA we could find eight families with mild to moderate mid-frequency U-shaped ADNSHI, three families with moderate to severe gently sloping high tone ADNSHI and one family with variable ADNSHI. The corresponding DP-grams showed a family-specific DP-gram in 20 (66%) of the examined persons. Seven (23%) showed no distortion-product otoacoustic emissions (DPOAE). In three (10%) persons the DP-grams varied but were also abnormal. The CVT was normal in all cases. Obviously it is possible to find out typical DP-grams in families with ADNSHI. This could be used for early diagnosis of hearing disorders in newborns of such families. Problems could only occur in progredient cases.

Audiometry, Pure-Tone↗
PubMed1999

Endemic Trypanosoma cruzi infection in Indian populations of the Gran Chaco territory of South America: performance of diagnostic assays and epidemiological features.

The relative specificities and sensitivities of several serological assays for the diagnosis of Trypanosoma cruzi infection were estimated in Indian populations of Argentina and Paraguay. The results obtained with the assays, which proved to be most reliable, were used to study the distribution of the parasite in these populations. Serological evidence of T. cruzi infection was demonstrated in 256 (37.7%) of 679 Indians living in relatively small and isolated communities in the Salta province of northern Argentina and in western Paraguay, regions that are part of the tropical territory called Gran Chaco. In contrast, none of the 94 Indians examined in south-western Argentina was positive. Infection in the Gran Chaco Indians increased with age and clustered in families. Marked differences in seroprevalence were observed between the 16 Indian communities examined in Gran Chaco. These differences seem to be associated both with the risk of transmission from the sylvatic reservoirs of the parasite and with the frequency with which vector-spraying campaigns have been implemented.

Adolescent↗
PubMed1984

Studies on the induction of histocompatibility gene mutations in germ cells of mice by chemical mutagens and/or virus-inducing compounds.

This work continues earlier studies concerning the use of histocompatibility mutations in mammalian germ cells as a mutagenicity test system (H test). The rate of spontaneous H mutations was re-examined using a new basis for the classification of H mutants. This procedure led to very high frequencies of suspected spontaneous H mutants: among C57Bl/6 mice, 6% and among C3H mice, 9%. F2 hybrids of a cross between these strains revealed 1% suspected H mutants. Using the same procedure, the sensitivity of the H test was examined with the mutagens ethylnitrosourea, benzo[a]pyrene, 2-acetylaminofluorene (2-AAF), with the solvent dimethyl sulfoxide (DMSO) and with the antibacterial nitrofurantoin. It was possible to demonstrate the mutagenic potential of all mutagens tested as well as their specific action on the different stages of male germ cell development. We succeeded in demonstrating the mutagenicity of 2-AAF for the first time in germ cells of a mammal. In contrast to the negative result with benzopyrene (BP) in the specific locus test, BP induced H mutants even at the very low dose of 2 mg/kg. DMSO was found to induce H mutations in spermatogonia. This extraordinary result is possibly due to the virus-inducing properties of this compound. Nitrofurantoin which is often used in treating bacterial infections of the urinary tract in humans showed a very stage-specific action on maturing spermatids. The value of the H test for mutagenicity testing is discussed with respect to its sensitivity and economy. The very high spontaneous frequency of suspected H mutants and the ease of inducing increased mutant frequencies by mutagens and by DMSO suggest the possibility that the majority of the histoincompatibilities found in the H test are due to induced antigenic gene products of endogenous viruses. This, however, does not interfere with the applicability of the H test for mutagenicity testing, but rather seems to augment its sensitivity to alkylating mutagens as well as mutagens which probably cause frameshift mutations. Other tests for mutations and/or inherited tumor proneness using mouse germ cells can easily be combined with the H test, because the test animal does not have to be killed, thus reducing the cost of the test.

2-Acetylaminofluorene↗
PubMed1982

Histocompatibility gene mutation rates, spontaneous and induced by the chemical mutagen procarbazine.

The use of histocompatibility mutations in mice for the development of a mutagenicity test has been proposed by several immunologists. The aim of our work was to find a basis for the establishment of the H-test as a mutagenicity test. We therefore determined the spontaneous mutation rates of H-genes in the two inbred mouse strains C3H and C57Bl. Furthermore, we tried to increase the mutation rate by the well-known chemical mutagen procarbazine. The spontaneous mutation rates of H-genes of both strains were identical at about 1.2 x 10(-3). After long-term mutagen treatment with 100 mg procarbazine/kg per week, the mutant frequency increased to about 7% and decreased again when the total dose had reached more than 9 x 100 mg/kg in C57Bl mice and more than 14 x 100 mg/kg in C3H mice. These results are discussed in comparison with procarbazine experiments with other mutagenicity test systems. The feasibility of the H-test for mutagenicity testing remains to be verified by further experiments with other germ-line mutagens.

Animals↗
PubMed1977

Suppressor T cells in low zone tolerance. I. Mode of action of suppressor cells.

Low zone tolerance (LZT) to bacteriophage fd seems to be a type of tolerance which is primarily caused by suppressor T cells. The aim of this paper is to analyze their mode of action. For the induction of antigen-specific suppressor cells in hydrocortisone pretreated CBA mice, we use tolerogenic and immunogenic doses of antigen. Suppressor activity can be demonstrated upon transfer of spleen cells into normal syngeneic mice. After immunization these animals are unable to produce IgG antibody against phage fd, whereas the IgM response is not suppressed; The half-life of transferred suppressor cells in nonimmunized animals is 5--6 weeks. The target of suppression are unprimed T helper cells, whereas primed helper cells cannot be blocked. T helper cells become "resistant" to suppression 18--36 h after contact with antigen. Differentiation from unprimed B into B memory cells is unaffected, yet under suppression conditions persisting B memory cells are blocked in IgG production. The experimental data are incorporated into a model of LZT.

Animals↗