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F M van Breugel

Publications and source records attributed to F M van Breugel.

10 recordsLinked to original sources
PubMed1987

Differential riboflavin deposition in white and variegated white mutants of Drosophila hydei.

Riboflavin deposition in organs of Drosophila hydei was studied by means of a growth test using a riboflavin-deficient strain of the fungus Aspergillus nidulans. In wild-type animals, riboflavin is deposited in Malpighian tubules (MT) and testes but not in adult eyes. Certain white (w) mutants do not contain riboflavin, whereas intermediately colored w mutants contain minor amounts of the substance. Riboflavin-containing MT cells contain special globules that can be fixed and stained with the redox dye phenazine-methosulphate. The number and size of these granules is related to growth effect and point to a role of the w locus in the intracellular deposition of riboflavin in special organs. In white-mottled (wm) position-effect variegation mutants, a significant correlation was found between the extent of variegation (percentage of yellow cells) and riboflavin content (growth effect) of the MT. However, the individual variation of cell phenotype was extremely large and exaggerated types were observed indicating "overdominance" of the rearranged w+ gene. This contradicts an unsubstantiated dogma of position-effect variegation that assumes that the affected gene simply switches between the on and off state, as is discussed.

Animals↗
PubMed1973

Cell clustering and pleiotropy in white-variegated eyes and Malphighian tubes of Drosophila hydei.

The type of variegation of eyes of white-mottled mutants of D. hydei, either small-spotted or large-spotted, depends on the specific chromosome rearrangement involved. This distinction between mutants, though handsome, is not absolute because very seldomly small-spotted types do show a larger pigment aggregate and some "large-spotted" flies have no large spots at all, but only minor spots. Because of a pleiotropic action of the white gene, we could study the variegation of Malpighian tubules. The quasi-linear array of Malpighian cells enables a thorough statistical analysis. The problem was in how far the variegation of the tubes that is correlated with the variegation of eyes (in as far as numbers of pigmented and unpigmented cells are concerned) is also connected with a cell-lineage type of determination. Statistics now show that in spite of temperature-induced great variation in the percentage of pigmented cells, all types studied show a nearly random distribution of pigmented and unpigmented cells in the Malpighian tubules. This implies that the cell-lineage type of determination is not only largely mutant-specific but also organ-specific, i.e., limited to eyes. A basic gradient, however, as characteristic for eyes, was also found in Malpighian tubes.

Animals↗