[Cirrhosis caused by thorotrast: apropos of a case]

We present the clinical case of a female patient with cirrhosis of the liver. The radiografic and histopathological studies demonstrated that de etiology of this cirrhosis was in relation with the use of thorotrast given during angiografic studies which the patient underwent 35 years ago.

Effects of engrailed in the genital disc of Drosophila melanogaster

engrailed has been postulated to be the "selector gene" involved in the establishment of the anterior-posterior compartment border in several imaginal discs and in at least the first two abdominal segments of Drosophila melanogaster. Our study of the effects of different mutant engrailed genotypes on genital disc development provided the following major results: All three terminal primordia (female and male genitalia, and analia) were affected. Different heteroallelic combinations showed different expressivities, and three terminal primordia were differently affected by the same mutant genotype. The engrailed genotypes deleted specific elements of the adult terminalia without causing associated pattern duplications. The reduced morphology of the male engrailed genital disc was analogous to the pattern deletions observed in the adult terminalia. That the engrailed phenotype is stable was demonstrated by culturing in vivo intact and fragmented engrailed genital discs. Cell death was found in a significant number of mature male en2/en3 genital discs. The results are discussed in terms of the segmental organization of the genital disc and in terms of the "selector gene" function postulated for the engrailed locus. The interpretation that each terminal primordium has an anterior and a posterior compartment is presented and it is assumed that in the genital disc engrailed transforms posterior cells into anterior cells that do not develop, thereby causing the deficiency pattern of the engrailed phenotype.

Sex determination and dosage compensation in Drosophila melanogaster : production of male clones in XX females

Sex determination and dosage compensation in Drosophila are implemented by the ratio of X-chromosomes to sets of autosomes (X:A ratio). Our aim was to change this X:A ratio during development, and to assess the response of the affected cells in sexually dimorphic structures. For this purpose, clones of XO constitution were produced in female embryos and larvae of two genotypes in which almost the entire euchromatic arm of one X-chromosome was translocated to the third chromosome. Genotype I was heterozygous for the X-linked recessive mutations Sxl, genotype II was homozygous for Sxl. The Sxl gene (sex-lethal) is involved in mediating sex determination and dosage compensation. In genotype I (Sxl), male clones could be generated up to 48 h in genitalia and analia, up to 72 h in the sex comb region and up to 96 h in 5th and 6th tergites. In genotype II (Sxl), male clones only appeared in the tergites, and only up to 24 h. The difference in these results is ascribed to the presence of Sxl in genotype I: when homozygous, this mutation causes XX clones to differentiate male structures; most of the male clones produced in genotype I must therefore be XX. In contrast, male clones produced in genotype II must be XO. Since these were only found when generated in embryos we conclude that the X:A ratio expresses itself autonomously in clones by setting the state of activity of the Sxl gene around blastoderm stage. Once this is achieved, the X:A signal is no longer needed, and the state of activity of the Sxl gene determines sex and dosage compensation.

Crossing-over in the female hybrids between Drosophila simulans and Drosophila mauritiana

The cross between D. simulans and D. mauritiana yields fertile hybrid females. Crossing-over occurs in such female hybrids. This system allows the transfer of pieces of chromosomes from one species into another, thus providing an experimental tool to analyze the genetic basis of evolutionary problems, as well as the regulation of gene expression during development.

Genetics and biochemistry of cryptopleurine resistance in the yeast Saccharomyces cerevisiae

Protein synthesis by ribosomes from several cryptopleurine-resistant yeast mutants is also resistant to emetine and tubulosine. These mutants can be classified into two different types: Class I mutants which display high levels of resistance to emetine and tubulosine and Class II mutants that are only weakly resistant to tubulosine and are slightly more sensitive to emetine than those of Class I. Apparently all mutants have similar levels of resistance to cryptopleurine. The distinct phenotypes of Class I and Class II strains are expressed through their 40S ribosomal subunit. Genetic analysis has shown that the mutations to cryptopleuring resistance are allelic and that in a particular case (strain CRY6) the pleiotropic phenotype is a result of the expression of the cry1 locus. It is suggested that Class I and Class II mutants arise from two independent mutational events within The cry1 allel. In heterozygous (+/cry1) diploids both the sensitive and the resistant genes are expressed as shown by studies of the action of cryptopleurine on polyphenylalanine-synthesizing systems derived from each parental sensitive and resistant haploid strain and heterozygous diploid strains. The apparent dominance of sensitivity over resistance which may be observed in vivo in heterozygous (+/cry1) diploids has been explained in terms of the mode of action of the inhibitors.

Cryptopleurine resistance: genetic locus for a 40S ribosomal component in Saccharomyces cerevisiae

Mutants resistant to the phenanthrene alkaloids tylophorine, tylocrebrine, and cryptopleurine have been isolated from the yeast Saccharomyces cerevisiae. A single recessive nuclear gene was responsible for resistance. This resistance locus, cry, was closely linked to the mating locus (2.2 centimorgans). The resistance was ribosomal and was due to an altered 40S ribosomal subunit. The mode of action of these drugs has been examined, and they appear to inhibit the translocation phase of protein synthesis.