Biomedical subjects

M Sarà

Publications and source records attributed to M Sarà.

8 recordsLinked to original sources

PubMed2004

Mitochondrial simple sequence repeats and 12S-rRNA gene reveal two distinct lineages of Crocidura russula (Mammalia, Soricidae).

A short segment (135 bp) of the control region and a partial sequence (394 bp) of the 12S-rRNA gene in the mitochondrial DNA of Crocidura russula were analyzed in order to test a previous hypothesis regarding the presence of a gene flow disruption in northern Africa. This breakpoint would have separated northeast-African C. russula populations from the European (plus the northwest-African) populations. The analysis was carried out on specimens from Tunisia (C. r. cf agilis), Sardinia (C. r. ichnusae), and Pantelleria (C. r. cossyrensis), and on C. r. russula from Spain and Belgium. Two C. russula lineages were identified; they both shared R2 tandem repeated motifs of the same length (12 bp), but not the same primary structure. These simple sequence repeats were present in 12-23 copies in the right domain of the control region. Within the northeast-African populations, a polymorphism of repeat variants, not yet found in Europe, was recorded. A neighbor-join tree, which was built by sequences of the conserved 12S-rRNA gene, separated the two sister groups; it permitted us to date a divergence time of 0.5 Myr. Our data discriminated two different mitochondrial lineages in accordance with the previous morphological and karyological data. Ecoclimatic barriers formed during the Middle Pleistocene broke the range of ancestral species in the Eastern Algeria (Kabile Mountains), leading to two genetically separate and modern lineages. The northeast-African lineage can today be located in Tunisia, Pantelleria, and Sardinia. The northwest-African lineage (Morocco and West Algeria), reaching Spain by anthropogenic introduction, spread over north Europe in modern times. The Palaearctic C. russula species is monophyletic, but a taxonomical revision (ie, to provide a full species rank for the northeast taxa and to put in synonymy some insular taxa) is required.

Africa, Northern↗

PubMed2001

Heat stress-activated, calcium-dependent nitric oxide synthase in sponges.

The presence of Ca(2+)-dependent, heat-stress-activated nitric oxide synthase (NOS) activity in peculiarly shaped, fusiform, and dendritic sponge cells is described for the first time. The NOS activity was evidenced evaluating the conversion of radioactive citrulline from [(14)C]arginine in intact cells from two different species that are phylogenetically unrelated in the class of Demospongiae: Axinella polypoides and Petrosia ficiformis. The production of nitrogen monoxide (NO) was confirmed by electron paramagnetic resonance analysis, and the histochemistry technique of NADPH diaphorase showed a specific localization of NOS activity in a particular network of dendritic cells in the sponge parenchyma. Sponges are the most primitive metazoan group; their evolution dates back 600 million years. The presence of environmental stress-activated NOS activity in these organisms may prove to be the most ancient NO-dependent signaling network in the animal kingdom.

Animals↗

PubMed2000

Parasitic diatoms inside antarctic sponges.

Antarctic sponges may host large populations of planktonic and benthic diatoms. After settling on the sponge, these diatoms enter its body through pinacocytes (1) and form, there, large mono- or pauci-specific assemblages. Yet the total amount of carbohydrates in the invaded sponge tissue is inversely correlated with that of chlorophyll-a. We suggest, therefore, that endobiont diatoms utilize the products of the metabolism of their host as an energy source. This is the first evidence indicating that an endobiotic autotrophic organism may parasitize its animal host. Moreover, this unusual symbiotic behavior could be a successful strategy that allows the diatom to survive in darkness.

Animals↗

PubMed1996

A "sensitive" cell system. Its role in a new evolutionary paradigm.

The cell property of processing the environmental information is called sensitivity and referred to a "sensitive" cell system in which physical signals and specialized molecules work in relation to peculiar cell structures. It is suggested that, in addition to its role in cell behaviour, the sensitive system performs a basic role in morphogenesis in all cells. It interacts with the genetic system in gene expression and regulation directly or indirectly through epigenetic processes. Epigenetic inheritance, adaptive mutations and genetic assimilation allow environmental information to be embodied in new traits, thereby becoming relevant in evolution. This is consistent with an evolutionary mechanism with two alternate and recurrent phases: the first, epigenetic and Lamarckian at cell and organism levels and the second, selective and Darwinian, at population level.

Bacteria↗

PubMed1989

The problem of adaptations: an holistic approach.

On the basis of recent advances in molecular genetics and embryology the role of phenotypic plasticity in the origin of adaptations has been reviewed and emphasized. Carrying on Waddington's experimental research on genetic assimilation, the epigenetic landscape, where genotype, phenotype and environment meet, should be investigated as the place in which environmental information may be embodied in the organism and evolutionary novelties could arise. An holistic, multilevel approach, with the organism as the basic level for the genesis of adaptations and the population as upper level as improving and/or altering, through selective and random factors, the evolutionary pattern, is then envisaged.

Adaptation, Biological↗

PubMed1987

Ultrastructural study of the mature egg of Tethya citrina Sarà and Melone (Porifera, Demospongiae).

Tethya citrina is an oviparous demosponge in which eggs are distributed in clumps within the choanosome. The cytoplasm of the mature egg presents a peripheral cortex consisting of a slightly granular layer sandwiched between two densely granular, vesiculated ones. The cortex probably has a specialized, trophic function. Mesohyl bacteria are phagocyted at the egg surface, included in vacuoles, and transferred across the cortical sheath toward the inner cytoplasm. The region of the egg extending between the cortex and the nucleus shows a lacunary system mostly developed beneath the cortical envelope. The noncortical cytoplasm also contains lipid droplets, dense rodlike bodies, and phagosomelike granules. Most of the latter are probably autophagosomes, forming lacunae and supporting autosynthetic vitellogenesis. Rodlike inclusions are probably proteinaceous; they likely originate within the phagosomes and represent the actual yolk material.

Animals↗

PubMedDate not supplied

Phenotypic plasticity in hydrozoans: morph reversibility.

The life cycle of Hydrozoans typically comprises two phases: the polyp, either solitary or colonial, with generally a benthic habitat, and the medusa which lives in the plankton. In its typical metagenetic cycle, the medusa is budded from the polyp, which is the product of sexual reproduction of medusae. However, several alternative reproduction patterns have also been described. In particular some species are able to perform a regressive transformation of the medusae that transform themselves into polyps bypassing sexual reproduction. In a species with alternative morphs switched by the environment, the more labile is the correlation between environmental factors acting on the genetic switch and the factors to which the resulting form is adapted, the more hazardous will be the development of either body form. However, we can explain the evolutionary advantage offered by reversion between morphs of these plastic species living in shallow water unpredictable environments: should produced medusae be released in the "wrong" environment, they would still have a chance of survival under another form.

Animals↗

PubMedDate not supplied

Biological evolution as an expression of body-plan potentialities.

A growing bulk of recent data from different fields as molecular biology, developmental biology, genetics, paleontology and phylogenetics shows that organisms play a more active role in their evolution than what postulated by the random variation-natural selection paradigm of the neo-Darwinian synthesis. Organisms show during development and morphogenesis autopoietic processes which are related to their body-plan potentialities. These potentialities are expressed through regulatory networks in which a plastic genome participates together with proteins and other substances in an epigenetic space. The epigenetic systems which arise from this interaction may be inherited and then assume a significant role in evolution becoming the source of new acquired characters. The acquisition of new traits through the epigenetic systems is influenced directly by environmental cues. If this process is coherent with the environmental demands it co-operates with natural selection in organism adaptation. An outstanding role in this context may be played by phenotypic plasticity if, as emerges in recent views, it may constitute a general basis for genetic assimilation processes.

Animals↗