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G Sella

Publications and source records attributed to G Sella.

12 recordsLinked to original sources
PubMed2006

Genotoxic effect of copper on salivary gland polytene chromosomes of Chironomus riparius Meigen 1804 (Diptera, Chironomidae).

The genotoxic action of copper (Cu) on the polytene chromosomes of Chironomus riparius was investigated by analysing structural and functional chromosome aberrations of fourth instars larvae hatched from eggs subject to acute (48 h) exposure with three environmentally relevant concentrations of aqueous Cu (0.005, 0.01, 0.05 mg/l). A dose dependent relationship was observed between Cu concentration and frequency of chromosomal aberrations. A significantly higher frequency of functional alterations, specifically decondensed centromeres and telomeres, and reduction in activity of Balbiani rings, was observed in treated material compared to control. A comparison of breakpoints resulting from treatment with chromium and lead from earlier studies with those Cu-induced identified a series of chromosomal weak points particularly vulnerable to trace metals. We also show that the appearance of structural and functional chromosome aberrations are more sensitive indicators of acute Cu toxicity in chironomid larvae than changes in external morphology.

Animals↗
PubMed2005

Outcrossing hermaphroditic polychaete worms adjust their sex allocation to social conditions.

Sex allocation theory predicts that simultaneous hermaphrodites shift sex allocation facultatively in response to variation in local group size. This study was performed to evaluate the relative investment in each sex function by the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema and to test whether allocation to each sex depends on the number of reproductive competitors. Four experimental groups were set up (in a 2 x 2 factorial design) with small or large group size and with small or large enclosures to control for potential confounding effects of density. We measured the proportion of female and male investment in focal individuals. Results revealed that individuals regulated their reproductive output so that when reproductive competitors were present, the number of female gametes was strongly reduced and the male function increased. In contrast, under monogamy, individuals in small groups produced lower numbers of sperm but had a higher egg output than worms in large groups. Density did not affect sex allocation in our experiment. Our findings provide qualitative support for Local Mate Competition theory, but also show that the pattern of sex allocation specific to this species is more complex than expected by current theory.

Analysis of Variance↗
PubMed2005

Comparison of allergen immunotherapy and drug treatment in seasonal rhinoconjunctivitis: a 3-years study.

Drug treatment and specific immunotherapy (SIT) are both effective in seasonal rhinoconjunctivitis, but the former acts only on allergic symptoms while the latter modifies the natural history of the disease. Only a few studies compared the clinical efficacy of the two treatments with contrasting results. We planned a study to compare the efficacy of SIT (15 patients) and drug treatment (15 patients) in moderate to severe seasonal rhinoconjunctivitis caused by sensitization to grass pollen. SIT was performed by a 5-grass extract standardized in IR and absorbed onto calcium phosphate (Phostal, Stallergénes, Antony, France) using the conventional build-up phase in 12 weeks and a maintenance treatment with monthly injection for three years. Drug treatment was done with cetirizine as antihistamine, mometasone furoate as nasal topical steroid, and levocabastine eyedrops. All patients registered during the pollen season their symptoms and drug consumption. After one year 12 of 15 patients treated with SIT had less symptoms and drug consumption in respect to baseline compared to none in drug treated group (p = 0.021) and after three years 15 of 15 were improved in group A compared to one of 15 in group B (p = 0.008). These findings indicate an higher efficacy of SIT in patients with seasonal rhinitis not only in the long term but also in the first year of treatment.

Administration, Intranasal↗
PubMed2004

Insertional polymorphism of a non-LTR mobile element (NLRCth1) in European populations of Chironomus riparius (Diptera, Chironomidae) as detected by transposon insertion display.

The midge Chironomus riparius is distributed all over the Palearctic region and is well characterized both at the morphological and cytogenetic levels. Here we describe a population study based on the insertional polymorphism of the retroposon NLRCth1, by means of a S-SAP (sequence-specific amplification polymorphism) derived technique (transposon insertion display; TID). While a previous study of allozyme polymorphism in Russian samples showed little variability, all the amplicons we identified are polymorphic. Genetic distances between 6 natural populations were calculated according to Nei and did not show a positive correlation with geographic distances. The genetic diversity detected among individuals of a given population was one order of magnitude higher than that among populations. However, the value of phi(ST) was significant (p < 0.001) and indicates that natural populations are more genetically differentiated than random samples of individuals.

Alleles↗
PubMed2000

On the dynamic persistence of cooperation: how lower individual fitness induces higher survivability.

We study a model in which cooperation and defection coexist in a dynamical steady state. In our model, subpopulations of cooperators and defectors inhabit sites on a lattice. The interactions among the individuals at a site, in the form of a prisoner's dilemma (PD) game, determine their fitnesses. The chosen PD payoff allows cooperators, but not defectors, to maintain a homogeneous population. Individuals mutate between types and migrate to neighboring sites with low probabilities. We consider both density-dependent and density-independent versions of the model. The persistence of cooperation in this model can be explained in terms of the life cycle of a population at a site. This life cycle starts when one cooperator establishes a population. Then defectors invade and eventually take over, resulting finally in the death of the population. During this life cycle, single cooperators migrate to empty neighboring sites to found new cooperator populations. The system can reach a steady state where cooperation prevails if the global "birth" rate of populations is equal to their global "death" rate. The dynamic persistence of cooperation ranges over a large section of the model's parameter space. We compare these dynamics to those from other models for the persistence of altruism and to predator-prey models.

Animals↗
PubMed2000

Effect of environmental pollution on the chromosomal variability of Chironomus riparius Meigen 1804 (Diptera, Chironomidae) larvae from two Piedmont stations.

Different frequencies of chromosomal alterations in salivary gland polytene chromosomes AB, CD and EF were described in larvae of Chironomus riparius (syn. Chironomus thummi) from the trace metal-polluted station of Santena on the river Banna, near Turin, and from the unpolluted station of Corio (40 Km from Turin) which was taken as a reference area. In a sample of 56 larvae from Santena, no specimen with the standard karyotype in all cells of the salivary glands was found. Different types of aberrations were found: 33 paracentric and five pericentric inversions, three deficiencies, four amplified sections and one chromatid break. Fifteen out of the 38 inversions and two amplified sections appeared to be inherited, while all the other aberrations were somatic. Most of the aberrations' breakpoints were located on both sides of the centromere regions, where constitutive heterochromatin is present. Also functional alterations were observed (mainly telomere and centromere decondensations and nine novel puffs). In a sample of 49 larvae of a population from the well-preserved area of Corio only six somatic and one inherited paracentric inversions were found. These results suggest that the strong destabilization of the genomes of C. riparius larvae from Santena could be a reaction to the activity of the toxic substances present in the polluted sediments of the river Banna.

Animals↗
PubMed2000

Compound action potential and cochlear microphonic extracted from electrocochleographic responses to condensation or rarefaction clicks.

In electrocochleography (ECochG) compound action potential (CAP) and summation potential (SP) are usually separated from the cochlear microphonic (CM) by the CM cancellation technique consisting in averaging the responses evoked by rarefaction and condensation clicks. With the aim of analysing the ECochG responses evoked by monophasic clicks, we developed a numerical method based on the theory of optimal filtering, which makes no assumptions about the unknown potentials. The application of the filtering technique to the ECochG recordings obtained from 6 normally hearing children and 10 children with cochlear hearing loss allowed us to perform CAP extraction in cases where CM was not cancelled by the conventional method. Differences in SP amplitude and polarity were found between rarefaction and condensation click-evoked responses in cochlear hearing losses.

Acoustic Stimulation↗
PubMed1997

C band variation in polytene chromosomes of Chironomus riparius (Diptera, Chironomidae) from a polluted Piedmont station (Italy).

C banding in polytene chromosomes of Chironomus riparius from a Santena polluted station of the river Po, Italy was described. A large variation in the appearance of C bands was established. The process involved the transformation of euchromatin into heterochromatin. Activation of all chromosomes at telomeres was found. A structural modification of telomeric heterochromatin may exist. The centromeric heterochromatin was rarely observed. A high percentage of an amplification (88%) in arm F, B3h, was recorded. These changes in the appearance of heterochromatin in the population studied could be considered as a type of polymorphic system, existing in the polluted population. For the first time in C. riparius two types of position effect variegation are reported. In arm E the euchromatin near to the centromere became inactive due to a heterozygous inversion and in arms D and F the opposite phenomenon was observed in which a heterozygous inversion partly suppressed the inactivation of heterochromatin.

Animals↗
PubMed1975

Inhibition of ouabain-sensitive ATPase by the saliva of patients with cystic fibrosis of the pancreas.

A study has been made of the effect of saliva from children with cystic fibrosis of the pancreas (CFP) on various components of the ATP hydrolyzing enzyme system. The ouabain-sensitive ATPase activity of erythrocyte membranes prepared from intact erythrocytes preincubated with CFP saliva was 35 +/- 4 nmol Pi/mg fry wt membrane suspension/hr, compared with 48 +/- 7 nmol Pi/mg dry wt membrane suspension/hr when the erythrocytes were preincubated with control saliva. A calcium-activated component of ATPase was decreased from 202 +/- 30 nmol Pi/mg dry wt membrane suspension/hr in erythrocytes preincubated with control saliva, to 151 +/- 17 nmol Pi/mg dry wt membrane suspension/hr when the incubation was carried out with CFP saliva. In a second series of experiments, ultrafiltered saliva was added directly to an ATPase assay. The saliva from children with CFP brought about a mean decrease in ouabain-sensitive ATPase of 16% compared with control saliva.

Adenosine Triphosphatases↗
PubMedDate not supplied

On the evolution of redundancy in genetic codes.

We simulate a deterministic population genetic model for the coevolution of genetic codes and protein-coding genes. We use very simple assumptions about translation, mutation, and protein fitness to calculate mutation-selection equilibria of codon frequencies and fitness in a large asexual population with a given genetic code. We then compute the fitnesses of altered genetic codes that compete to invade the population by translating its genes with higher fitness. Codes and genes coevolve in a succession of stages, alternating between genetic equilibration and code invasion, from an initial wholly ambiguous coding state to a diversified frozen coding state. Our simulations almost always resulted in partially redundant frozen genetic codes. Also, the range of simulated physicochemical properties among encoded amino acids in frozen codes was always less than maximal. These results did not require the assumption of historical constraints on the number and type of amino acids available to codes nor on the complexity of proteins, stereochemical constraints on the translational apparatus, nor mechanistic constraints on genetic code change. Both the extent and timing of amino-acid diversification in genetic codes were strongly affected by the message mutation rate and strength of missense selection. Our results suggest that various omnipresent phenomena that distribute codons over sites with different selective requirements--such as the persistence of nonsynonymous mutations at equilibrium, the positive selection of the same codon in different types of sites, and translational ambiguity--predispose the evolution of redundancy and of reduced amino acid diversity in genetic codes.

Codon↗
PubMedDate not supplied

NOR regions of polychaete worms of the genus Ophryotrocha studied by chromosome banding techniques and FISH.

This article reports the results of cytogenetic analyses carried out on 10 species of polychaete worms belonging to the genus Ophryotrocha (Dorvilleidae). Nucleolar organizer regions (NORs) were characterized by Ag staining, C-banding, CMA3 staining, and ribosomal fluorescent in situ hybridization (rDNA FISH). Extensive intraspecific variation in NOR number and distribution were observed in O. costlowi, O. sp. macrovifera, O. notoglandulata, O.l. labronica, O. l. pacifica (2n = 6), O. p. puerilis, O. diadema (2n = 8), O. hartmanni, O. gracilis (2n = 10). In O. sp. robusta (2n = 10), Ag-NORs were always located on a single chromosome pair. CMA3 staining suggests a possible trend toward a GC-rich rDNA compartmentalization. In O.l. labronica, O. p. puerilis, O. diadema, and O. sp. robusta rDNA FISH shows that Ag and FISH signals coincide. Results from C-banding seem to indicate that the increased genome size (GS) observed in O. sp. macrovifera (0.8 pg) and O. hartmanni (1.16 pg) compared to the base GS value of the genus (0.4 pg) cannot be attributed to variation in the heterochromatin content.

Animals↗