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Biomedical subjects

F Anders

Publications and source records attributed to F Anders.

At least 55 records · Page 3Linked to original sources
PubMed1979

Space osteoporosis: an electromagnetic hypothesis.

Loss of body calcium during spaceflight is a potential problem in long voyages. This loss does not appear to be caused by a deficiency in diet or exercise. The idea is advanced that the altered electromagnetic environment experienced in space may be at least partially responsible. We show that the electric field induced inside astronauts because of their motion in the geomagnetic field is greater than that which has produced a wide variety of biological effects in earth-bound experiments.

Calcium↗
PubMed1978

Genetics of susceptibility in the platyfish/swordtail tumor system to develop fibrosarcoma and rhabdomyosarcoma following treatment with N-methyl-N-nitrosourea (MNU).

About 7000 animals of 65 different genotypes of the xiphophorine fish were treated with the direct acting chemical carcinogen N-methyl-N-nitrosourea (MNU; 10(-3)M; four times for 1 hour in two week intervals), in order to find out whether the susceptibility for development of fibrosarcomas and rhabdomyosarcomas is directly related to the genotype. A genotype specific susceptibility was found, ranging from zero to about nine percent. The highest susceptibles were found in certain backcross hybrids involving P.variatus/X.helleri-hybrids and X.helleri, as the recurrent parent. These genotypes were further analysed. Both P.variatus and X.helleri, as werr as their F1 proved to be insusceptible; while from the three backcrosses, which were tested, namely the BC1, BC4 and BC15, both the BC1, and the BC4, were susceptible, but the BC15 was insusceptible. The results are interpreted on the basis of the assumption that the differential susceptibility is a function of the type of control of a tumor gene (Tu-Fi-Rh) endogenous to P.variatus and involved in development of fibrosarcomas and rhabdomyosarcomas. Accordingly, in P.variatus and in the F1 the Tu-Fi-Rh is controlled by repressing genes (R-genes) linked as well as non-linked to Tu-Fi-Rh; because simultaneous mutation of both R-genes following treatment with MNU is an extremely unlikely event, these genotypes have an extremely low susceptibility. By contrast, in the BC1 and the BC4 the non-linked R-genes become eliminated and only the linked R-gene remains for repression of Tu-Fi-Rh; this condition confers a high degree of susceptibility, because one single mutation may lead to impairment of the R-gene and to Tu-Fi-Rh-mediated formulation of fibrosarcomas and rhabdomysarcomas. In the BC15, furthermore, also the Tu-Fi-Rh has become eliminated, resulting in a loss of the susceptibility. The results suggest that in the xiphophophorine fish the susceptibility for responding to MNU-treatment with the development of fibrosarcomas and rhabdomysarcomas is related directly to the genotype.

Age Factors↗
PubMed1977

Melanogenesis in genetically determined pigment cell tumors of platyfish and platyfish-swordtail hybrids: correlation between tyrosine activity and degree of malignancy.

In the genetically determined pigment cell tumors of platyfish and platyfish-swordtail hybrids, the degree of malignancy of pigment cells which have been neoplastically transformed by a tumor gene (Tu) depends on the type and number of certain regulating genes (R). In the present study, the tyrosinase activities in tumors of different degrees of malignancy (black spots, premelanomas, melanomas) have been determined. The results demonstrate a close correlation between the level of tyrosinase activity and the degree of malignancy. Spot patterns consisting of completely differentiated (benign) Tu-transformed cells show no tyrosinase activity. Premelanomas containing a few incompletely differentiated (malignant) Tu-transformed cells in addition to many differentiated ones show moderate tyrosinase activities. Melanomas which contain increasing numbers of incompletely differentiated cells with increasing growth rates show high to extremely high tyrosinase activities. Thus, the tyrosinase levels present in these tumors can be used as an indicator for the degree of differentiation and, thereby, for the degree of malignancy of the neoplastically transformed pigment cells.

Animals↗
PubMed1977

Tissue-specific esterases in the Xiphophorine fish Platypoecilus maculatus, Xiphophorus helleri, and their hybrid.

Tissue-specific esterases of the xiphophorine fishes Platypoecilus maculatus (platyfish), Xiphophorus helleri (swordtail), and their F1 hybrid have been analyzed using disc electrophoresis. Seven esterase zones (resolved into a maximum of nine bands) exist in these fishes, and these have been classified by employing specific inhibitors. Five of the seven zones, EST-1, EST-2, EST-5, EST-6, and EST-7, appeared to be carboxylesterases; while the two remaining zones, EST-3 and EST-4, were classified as cholinesterases. In the liver of the platfish, all seven esterase zones were detected, while the liver of the swordtail exhibited only five esterase zones. EST-1 and EST-3 were lacking in the liver tissue of the swordtail. All seven esterase loci were expressed in the liver tissue of the F1 hybrid. The reciprocal crosses gave the same results. In the fin, skin, skeletal muscle, and eye tissues from all three genotypes, three major esterase zones, EST-2, EST-5, and EST-7, were detected. In addition, EST-1 was frequently detected in all these tissues of the platfish and the F1, but was lacking in the swordtail. Serum from three genotypes showed one prominent esterase zone, EST-5; however, trace activity of EST-2 and EST-7 zones could also be detected. It seems that in all tissues of the F1 hybrid there is expression of all the esterase genes from the platfish. The results of the present study are discussed in the comparison to those from other studies on teleost esterases.

Animals↗
PubMed1976

An approach to genetic transformation in the Xiphophorine fish.

The particular suitability of the Xiphophorine fish system for achieving genetic transformation is presented, and it was analyzed whether information carrying donor DNA might be available to the propigment cells of embryos of Xiphosphorus helleri, which are the target cells for the transformation. Heterologous 2H3H-labelled donor DNA from E. coli, which was taken for technical reasons instead of homologous fish DNA, undergoes degradation both after injection into the neural crest region and after injection into the yolk sac (molecular weight at O h: 50 X10(6); at 2 h: 1 X 10(6); at 5 h: less than 3 X 10(5); at 10 h: less than 1 X 10(4)). It is concluded therefore, that informative donor DNA is present for about 2 to 3 hours after injection. The DNA of the recipient embryo is labelled radioactively during that time at which informative DNA is present only, if the donor DNA is injected into the neural crest region. The probability that a foreign gene might become available to the propigment cells and might induce transformation is discussed.

Animals↗
PubMed1976

A possibility to achieve genetic transformation in the platyfish-swordtail system (Platypoecilus maculatus - Xiphophorus helleri).

In order to determine how informative homologous donor DNA might be made available to propigment cells of the recipient Xiphophorus helleri for transformation, labelled heterologous DNA from E. coli was injected into the neural crest region or the yolk sac of embryos of the recipient. On the basis of the degradation rate of the donor DNA and the incorporation rate of radioactivity into the recipient DNA, it is concluded that injection into the neural crest region may be a suitable method to make available informative homologous donor DNA for transformation.

Animals↗