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Biomedical subjects

A Ghysen

Publications and source records attributed to A Ghysen.

At least 55 records · Page 3Linked to original sources
PubMed1986

Muscle connections between imaginal discs in Drosophila.

A comparison of the protein content of different imaginal discs of Drosophila revealed that among more than 600 protein species that can be detected, only three show differences in concentration among different types of discs. Two of them form a doublet that can be resolved only by using extended electrophoresis conditions. This doublet was also reported to have a nonhomogeneous distribution within some discs. Here we show that these two proteins are tropomyosin components, and that they are associated not with the discs themselves but with a new type of muscle that connects some of the discs together.

Antibodies, Monoclonal↗
PubMed1985

Segmental determination in Drosophila central nervous system.

We have analyzed the control of two segment-specific features in the central nervous system of Drosophila larvae. One of them is present only in the thoracic ganglia of the larva, where it represents the anlage of the adult leg neuromeres; the other is found in the first abdominal, as well as in the thoracic, ganglia. We show that mutations within the bithorax complex have parallel but independent effects on these neural structures and on the larval epidermis. We also show that the central nervous system is very sensitive to mild perturbations of the bithorax complex, and in particular to haploinsufficiency.

Animals↗
PubMed1985

Formation of neuronal pathways in the imaginal discs of Drosophila melanogaster.

We have followed the formation of neuronal pathways in different imaginal discs of Drosophila. The pattern is highly reproducible for a given disc type but distinct for each type of discs: in leg discs, several neurons are present before metamorphosis and provide two major pathways that are joined by later neurons; in the wing and haltere discs, a few pairs of neurons appear after the onset of metamorphosis and pioneer the major pathways; in antenna discs, no pioneers are detected before massive neuronal differentiation begins. The mechanisms used for axonal guidance seem common to all discs, and the differences between discs can be accounted for simply by differences in the arrangement and birth time of pioneer neurons. Different subsets of pioneer neurons are deleted by mutations such as scute and engrailed.

Animals↗
PubMed1983

Segmental determination of sensory neurons in Drosophila.

The analysis of flies where one segment is transformed into another by mutation or by experimental treatment shows that the central projection of a sensory neuron depends on its segmental determination. The genetic functions that control the segmental determination of neurons and of epidermal cells appear to be distinct, but they have common regulatory features.

Animals↗
PubMed1982

Segmental differences in the protein content of Drosophila imaginal discs.

The protein content of various Drosophila imaginal discs was analysed by two-dimensional electrophoresis followed by silver-staining. Three proteins, identified as tropomyosins alpha and beta and actin I, are more abundant in the metathoracic discs (haltere and third leg) than in the mesothoracic discs (wing and second leg). In the case of the wing disc, these proteins are probably contributed by the adepithelial (muscle precursor) cells, as indicated by their non-uniform localisation within the disc. Mutations in the bithorax complex have no effect on the difference between second and third leg discs. We conclude that there is a segmental difference in the protein content of homologous discs, that this difference is probably localized in the adepithelial cells, and that it is not under the direct control of known alleles of the bithorax complex.

Journal Article↗
PubMed1980

Sensory pathways in Drosophila central nervous system.

We have analyzed the central projections of identified sensory neurons in wild type Drosophila and in the homeotic mutant bithorax postbithorax. The results indicate that: (i) the choice of a given pathway in the central nervous system of the adult depends on the developmental history of the neuron, namely on the type of sense organ of which it is part, and on the developmental compartment to which it belongs; (ii) the establishment of the projection involves the specific recognition of a preexisting "trail" in the central nervous system. Here we examine and rule out alternative explanations of our results, and conclude that the directed growth of an axon relies at least in part on a physical guidance mechanism to which specificity is conferred by programming the growing axon to recognize the appropriate guide. We speculate that the guides are preexisting, specifically marked nerve fibers and that the basic pattern of connectivity is largely laid down early during neurogenesis, at a time when a standard set of connections is relatively easy to specify.

Afferent Pathways↗
PubMed1977

Amber mutations in Escherichia coli essential genes: isolation of mutants affected in the ribosomes.

A method to obtain amber mutations in ribosomal protein genes is described. tit relies on the P1-mediated localized mutagenesis (Hong and Ames, 1971) and on the fact that the recipient strain contains (a) an efficient but genetically unstable suppressor, (b) a particular thermoinducible lambda prophage which kills suppressor hosts at 42 degrees C. Exposure of these bacteria to the high temperature yields frequent suppressor-free derivatives while none will be found if the strain carries an amber mutation in an essential gene. Eleven mutants have been isolated by this method, of which at least six appear to carry amber mutations. All of them map close to, and to the right of spcA, in a region which codes mostly for ribosomal proteins. Three mutants were studied biochemically; all three show defective ribosomal assembly in vivo upon loss of suppression.

Bacteriological Techniques↗