Biomedical subjects

E Olmo

Publications and source records attributed to E Olmo.

At least 37 records · Page 2Linked to original sources

PubMed1991

Evolution of a centromeric satellite DNA and phylogeny of lacertid lizards.

1. The composition and phyletic distribution of a highly repetitive satellite DNA, isolated from Podarcis sicula, was studied. 2. This DNA was rich in adenine and thymine and displayed frequent adenine stretches. It was always located on the centromeric heterochromatin even in quite taxonomically distant species. 3. Southern blot hybridization of the Taq I satellite on various species of lacertid families showed a close affinity among Podarcis, Algyroides and Lacerta dugesii. 4. All the other taxa investigated did not seem to possess this repeated sequence.

Animals↗

PubMed1989

Genome size evolution in vertebrates: trends and constraints.

1. Studies on the genomic evolution in vertebrates have highlighted the differences existing between anamniotes and amniotes, both in quantitative and compositional terms. 2. These differences do not seem to depend on a different tendency to genic amplification, but rather on the existence of more strict and efficient constraints in amniotes. 3. Some constraints, that may be defined as "intrinsic", would act directly on the genome; among these particularly important is the chiasma frequency during meiosis. 4. Other, "extrinsic", constraints, would act indirectly through genic products or through cell morphometric parameters. 5. The genome size increase seems to depend on various mechanisms. The most wide-spread one seems to be the amplification of interspersed repetitive and non-repetitive sequences.

Animals↗

PubMed1987

Cytofluorometric DNA base determination in vertebrate species with different genome sizes.

The base composition of DNA was studied in 15 amphibian species and 28 reptile species by means of DAPI, a fluorochrome specific for adenine-thymine rich DNA (AT-rich DNA). The results obtained in reptiles and anuran amphibians coincided with biochemical data available for some species. In urodeles, on the contrary, the findings contrasted with biochemical data and suggest that DAPI is unable to stain all the AT-rich DNA in the erythrocytes of these organisms. It is concluded that the method is suitable for studying species with a small genome size, such as reptiles and anuran amphibians, but is not suitable for nuclei with a large genome size and a highly compact chromatin, such as urodele erythrocytes.

Amphibians↗

PubMed1983

Nucleotype and cell size in vertebrates: a review.

The relationships between genome size and various cell morphometric parameters have been assayed in 357 species of Vertebrates, in order to verify the existence and significance of the so-called "nucleotypic effect" in this subphylum. The results obtained clearly manifest a significant relationship between the increase in genome size and that in nuclear volume, nuclear surface, cell volume and cell surface. A precise correlation is also observed between the increase in DNA content and the decrease in the surface/volume ratios of the nucleus and the cell. Other parameters, such as the nucleoplasmic index and DNA concentration, though showing a slight increase with increasing genome size, have values rather homogeneous in each Vertebrate group. These results have allowed some interesting speculations on various problems; for example, the mechanisms through which genome size can influence the cell size; the influence of the DNA content and cell morphometric parameters on functional level of the cell and the organism; the importance of the nucleotypic effect in the adaptation to the environment of the various Vertebrate groups. From this study it seems possible to make the following conclusions: 1) in Vertebrates, genome size would exert a real nucleotypic influence on cell size; 2) genome sizes and cell morphometric parameters seem to be involved in the regulation of cell metabolism; 3) the regulation of some morphometric parameters depends strictly and automatically on the DNA amount or on other morphometric parameters. The regulation of others, instead, depends on the interaction of different factors, which do not always act synergically; 4) the nucleotypic effect seems to have different distribution and importance in Anamniotes and Amniotes.

Animals↗

PubMed1982

Sequence organization in the DNA of three Selachians.

The DNA interspersion pattern in 3 Selachians (R. asterias, T. marmorata and S. stellaris) has been studied through the reassociation kinetics of short (0.3 Kb) and long (2.5 Kb) DNA fragments. Preliminary results show that most of the DNA (approximately 80%) of these organisms is arranged according to a short-period interspersion pattern. A notable resemblance to the pattern previously described in the teleostean Salmo trutta has been observed.

Animals↗

PubMed1982

Repetitive DNA and polyploidy in selachians.

1. The DNA reassociation kinetics have been studied in 6 selachian species: Raja asterias, Raja montagui, Dasyatis violacea, Torpedo marmorata, Torpedo ocellata and Oxynotus centrina. 2. The results obtained show that the genomes of the two Torpedo, Dasyatis and Oxynotus are polyploid if compared with those of the two rays, though this finds no correspondence in the diploid chromosome number. 3. The phenomena of polyploidization would often be followed by wide chromosome rearrangements and by a progressive divergence of the various repetitive DNA sequences. 4. The existence of polyploidy in almost all the main superorders of living Selachians suggests that this mechanism of genomic evolution may have played an important role in the phylogeny of this class.

Animals↗

PubMed1982

Single-copy DNA and vertebrate phylogeny.

A study of genome sizes and repetitive and nonrepetitive nucleotide fractions in some reptiles, selachians, and amphibians showed that not one of these organisms possesses the percentage of single-copy DNA presumed to be typical of animals (70%). The data on the samples investigated, when compared with those existing in literature on other vertebrates, indicate certain general characteristics of the genome of this important animal group, which in this work are interpreted in terms of their adaptive functions. Each of the main systematic categories of the subphylum (classes or orders) has peculiar features as to the genome size and percentage of unique or repetitive DNA fractions. Among anamniotes (i.e., telosts, selachians, and amphibians) the percentages of the single-copy DNA are lower than among amniotes (i.e., reptiles, birds, and mammals) and inversely proportional to genome sizes, which does not occur in amniotes. Also on the basis of some karyologic evidence, the hypothesis is put forth that such differences may reflect the adoption, in the course of evolution of the amniotes, of new genetic strategies which have deeply influenced the genomic molecular structure.

Amphibians↗

PubMed1982

Relationships between DNA content and cell morphometric parameters in reptiles.

The relationships between the genome size and various cellular morphometric parameters have been, studied in 38 reptilian species. The nuclear volume, the cell volume and the cell surface area show a direct, linear and statistically significant correlation with the nuclear DNA content; the cell surface/cell volume ratio tends to decrease as DNA increases. The results are similar to those previously observed in Amphibia, which suggests, that at least in poikilothermic vertebrates, the correlations between DNA amounts and cell sizes are controlled by substantially similar mechanisms. A comparison of the average variations of the various morphometric parameters among each other and with the average variation of the genome size suggests that these parameters are not regulated all in the same way.

Animals↗

PubMed1979

Karyology of the primitive salamanders, family Hynobiidae.

Karyotypes have been studied in 3 species of Hynobius and in 1 species each of the remaining genera of Hynobiids (Ranodon, Batrachuperus, Salamandrella and Onychodactylus). All species have large diploid numbers, between 56 and 66, and asymmetrical and bimodal karyotypes. DNA contents (2C) were found to vary between 33 and 51 pg. Determination was not possible in Onychodactylus where higher values may be suspected. Some of the karyotypes investigated are similar to those of Cryptobranchids. Phylogenetic implications are discussed.

Animals↗

PubMed1979

Excess DNA in the nuclei of the subesophageal region of octopus brain.

Cytophotometric analyses of Feulgen-stained nuclei present in homogenates of vertical and subesophageal lobes of octopus brain have shown that the latter region contains larger nuclei with up to several times the amount of DNA present in vertical nuclei. No obvious relationship was found between DNA content and nuclear size. Except for a rather small minority, nuclei of the vertical lobe have a uniform size and the expected diploid amount of DNA. These parameters are not substantially dependent on body weight. In contrast, the DNA content of subesophageal nuclei increases progressively with body weight. The amount of DNA found in subesophageal nuclei does not seem to be a simple multiple of the diploid or haploid value.

Animals↗

PubMed1977

Base composition of DNA from some reptiles.

The DNA base composition was studied in 9 reptilian species (4 chelonians, 3 saurians, and 2 ophidians) by the thermal denaturation method. This preliminary investigation has brought to light differences in GC percentages and in the shape of melting curves between chelonian DNA and that from saurians and ophidians.

Animals↗

PubMed1976