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Biomedical subjects

R Marco

Publications and source records attributed to R Marco.

At least 55 records · Page 3Linked to original sources
PubMed1989

Quantitative analysis of ventral denticular patterns of Drosophila melanogaster larvae and the regulation of the bithorax complex.

A quantitative model of the effect of the bithorax complex on segmentation is presented which could explain the known data of the spatiotemporal regulation of key gene complex during early Drosophila development, in relation to their effects on some of the segmentation landmarks. The model tries to put together the two different genetic levels, the genotypic and the phenotypic. At the genotypic level, a minimal cross-regulatory network of the different genes involved, Antp, Ubx, abd-A and Abd-B which explains the reported levels of expressions of these genes. At the phenotypic level, the pattern of the ventral denticle belts across the larva which are characteristics of the different segments have been compared by calculating a value of the degree of similarity in the case of the wild-type and several mutant combinations. Finally the two parts of the model are combined, showing that a satisfactory agreement between the two can be achieved. Therefore, this work is a first attempt to develop a method which will provide an explanatory solution of the old question in morphogenesis of how the phenotype is directed by the genotype of a cell or organism.

Animals↗
PubMed1989

Microgravity effects on the oogenesis and development of embryos of Drosophila melanogaster laid in the Spaceshuttle during the Biorack experiment (ESA).

The results obtained during the last successful flight of the Challenger Shuttle, in early November 1985, indicate that oogenesis and embryonic development of Drosophila melanogaster are altered in the absence of gravity. Two hundred forty females and ninety males, wild type Oregon R Drosophila melanogaster flies were flown in the Spaceshuttle during the 7-day D-1 mission and the embryos laid during the spaceflight were recovered and studied. Although some eggs developed into normal 1st instar larvae and many into late embryos in the 23 +/- 2 h collection periods throughout the flight, several interesting differences from the parallel ground and in-flight centrifuge controls were observed: 1) There was an increase in oocyte production and size. 2) There was a significant decrease in the number of larvae hatched from the embryonic cuticles in microgravity. 3) The majority of embryos were normally fertilized and at late stages of development, except in the space-flown containers in microgravity where a percentage of earlier stage embryos were recovered showing alterations in the deposition of yolk. 4) In correspondence with these results, at least 25% of the living embryos recovered from space failed to develop into adults. 5) Studies of the larval cuticles and those of the late embryos indicate the existence of alterations in the anterior, head and thoracic regions of the animals. 6) There was a delay in the development into adults of the embryos and larvae that had been subjected to microgravity and recovered from the space shuttle at the end of the flight. No significant accumulation of lethal mutations in any of the experimental conditions was detected as measured through the male to female ratio in the descendant generation. It seems that Drosophila melanogaster flies are able to sense and respond to the absence of gravity, changing several developmental processes even in very short space flights. The results suggest an interference with the distribution and/or deposition of the maternal components involved in the specification of the anterioposterior axis of the embryo.

Animals↗
PubMed1989

Modeling the regulation of the bithorax complex in Drosophila melanogaster: the phenotypic effects of Ubx, abd-A and Abd-B heterozygotic larvae, and a homozygous Ubx- abd A hybrid gene.

As an intermediate step in the development of a defined quantitative model of pattern formation during Drosophila segmentation, we present here a model capable of predicting the experimentally determined levels of gene activity and their phenotypic consequences. In its present form, the model includes only four genes: the three genes of the bithorax complex (Ubx, abd-A and Abd-B) and Antennapedia. It is shown that the model is quite robust, predicting many properties in the behavior of these genes. A previously undescribed property is that all of these genes should phenotypically exhibit some kind of haploinsufficiency when present in only a single dose in the genetic background of the animal. This is shown both by the model and by a new method of quantitatively analyzing the differences in the more obvious cuticular features of the larvae, i.e., the patterns in the ventral denticle belts. The model is also capable of dealing with a complicated genetic situation, a hybrid gene of Ubx and abd-A produced by the C1 deletion.

Animals↗
PubMed1988

Genome organization of Artemia mitochondrial DNA.

To extend to the crustacean class the information concerning the genomic organization of the mitochondrial DNA (mtDNA) a double strategy has been used: Southern blot analysis with cloned Drosophila mtDNA probes and sequence comparison to the Drosophila mtDNA of the sequenced termini of different subclones along the Artemia mitochondrial genome, probably the smallest mtDNA studied at this level to date. These approaches have allowed us to localize the 16S rRNA gene, two tRNA genes and eleven protein genes. The genome organization is surprisingly similar to the Drosophila mtDNA, with the 16S rRNA and the protein genes located in the same positions and orientations as their Drosophila counterparts. The only changes detected are at the level of tRNA genes, although the position and orientation of some of these are also conserved. These results contrast with the important rearrangements detected among other invertebrates mtDNAs and suggest that the genome organization of the mitochondrial DNA may be more conserved in the arthropods than in other invertebrate phyla.

Amino Acid Sequence↗
PubMed1988

Properties of the clot assay, an easy quantitative assay of DNA endonucleases.

A systematic examination of the properties of the clot assay, a highly sensitive and simple method to detect DNase activities, is presented. It is shown that it is both quantitative and specific for monitoring the double-strand cleavage of DNA produced by specific and nonspecific endonucleases. Its simplicity and ease of quantification, which exceeds that of other methods of similar sensitivity, indicates that the clot assay can be advantageous in monitoring the activity of both types of endonucleases, especially if carried out in parallel with other more informative assays on the mechanism of action of the enzymes. As an example of its use, it is shown that pancreatic DNase I is capable, in the absence of external metal addition, of a limited attack on DNA containing bound divalent cations.

Animals↗
PubMed1987

Drosophila melanogaster contains a set of polypeptides capable of polymerizing into intermediate-like filaments.

A partial purification scheme applied to the Triton X-100 insoluble pellet of adult flies homogenates yielded a fraction which upon polymerization reproducibly produces filaments which in the electron microscope have all the typical properties of intermediate filaments. This is the first report of the presence of protein components with such properties in Drosophila. Thus, it is highly possible that insects and arthropodes, like other lower invertebrates, may contain the third extremely insoluble element of the cellular cytoskeleton.

Animals↗
PubMed1980

The unmasking of proteolytic activity during the early development of Artemia salina. Identification of a precursor after hatching.

The proteolytic activities of Artemia salina immediately after hatching are found masked in a precursor of high molecular weight (approximately 100000). The molecular weight of this precursor decreases slightly as development proceeds. However, its kinetic and chromatographic properties vary greatly. Shortly after hatching, the activities are highly inhibited, can be activated severalfold by the chaotropic agent potassium iodide and are not proportional to the amount of enzyme-containing extract added. Later after hatching, its kinetics become normal. From these observations we have concluded that (a) the majority, if not all, of the proteinase activities found later in development are already present immediately after hatching, although in an inhibited state that is gradually activated; (b) the proteinases are not found free in the cytoplasm but in a complex which may allow regulation of their activity.

Animals↗
PubMed1979

A fluorescamine-based sensitive method for the assay of proteinases, capable of detecting the initial cleavage steps of a protein.

The properties of the reaction of fluorescamine with proteins are the basis for the development of a sensitive, general and simple method for the assay of proteolytic activities. More importantly, the assay measures the initial step(s) of proteolytic attack, making it specially suitable for the examination of the controlling factors that regulate proteolytic degradation and/or the detection of 'specific' proteinases. The method allows the simple determination of the general parameters of enzyme action, V and Km, using proteins, i.e. the physiological substrates of the proteinases. The more appropriate proteins to be used as substrates are the N-amino-terminally blocked ones. Many proteins fulfill this requirement. If the particular protein whose degradation has to be studied lacks this modification, three different approaches can be used to study its degradation: (a) the accumulation of N-amino termini in excess over that of the intact substrate; (b) a gel filtration/continuous method and (c) the chemical blockage of its amino groups. The particular advantages of each of these approaches are discussed.

Endopeptidases↗