169,864 research outputs found
Characterisation of 5S rDNA in Gasterosteus aculeatus (Teleostei, Gasterosteidae)
No full textThe 5S rRNA genes of Gasterosteus aculeatus were characterised. Genomic DNA was amplified by PCR using two primers constructed in different salmonid species in order both to extract the total 5S rDNA (coding region + nontranscribed spacer region) and to generate amplified DNA products only if 5S rDNAs were tandemly arrayed. Amplification revealed four bands (A, B, C, and D) of about 250, 370, 580, and 660 base pairs, respectively. The electrophoretic pattern yielded by PCR products appeared very similar in the various species examined, it was also present in a selachian, an amphibian and a reptile. However, differences were observed in the size of the bands. Band A was cloned and sequenced: it consisted of 225 base pairs (A+T = 48.6%; G+C = 51.4%) and showed a high sequence homology to 5S rDNA in many vertebrate species. Hybridization on nylon filters of genomic DNA digested with several restriction enzymes showed the typical tandem array of repeated DNAs
On the estimation of a binary response model in a selected population
No full textNell’articolo si propone una generalizzazione del modello probit attraverso l’applicazione della funzione di ripartizione della variabile casuale Extended Skew Normal come funzione link. Tale modello si può utilizzare per variabili di risposta binarie quando si è in presenza di un meccanismo di distorsione selettiva. I parametri del modello vengono stimati attraverso il metodo della massima verosimiglianza, e si considera l’inferenza sui parametri del livello di selezione. Il modello viene analizzato nel caso in cui il meccanismo di selezione influenza i fattori non osservati ma non ha alcun effetto sulle variabili esplicative tuttavia continuano a valere altre condizioni di indipendenza. In particolare si dimostra che la formula della variabile strumentale continua a valere e il modello risulta al secondo stadio della procedura di stimaA generalization of the probit model is presented, with the extend skew normal distribution as a link function, which can be used for modeling a binary response variable in the presence of selectivity bias. The estimate of the parameters via ML is addressed, and inference on the parameters expressing the degree of selection is discussed. The assumption underlying the model is that the selection mechanism influences the unmeasured factors and does not affect the explanatory variables. When this assumption is violated, but other conditional independecies hold, then the model proposed here is derived. In particular, the instrumental variable formula still applies and the model results at the second stage of the estimating procedure
Evaluation of zebrafish DNA integrity after exposure to pharmacological agents present in aquatic environments
No full textOver the past few years, the increasing and uncontrolled use of pharmaceutical substances in agriculture, fish farming, human health and in veterinary medicine, together with an improper use of out-of-date medicines, has led to a consequent increase in the environmental problems linked to their disposal. In some Italian waste water treatment plants were found furosemide, a diuretic; ranitidine, an antiulcer drug; bezafibrate, a lipid regulator and ibuprofen, a painkiller. The present paper shows, by means of the synergic application of three tests (the Comet Test, the Diffusion Assay and the RAPD-PCR technique), how the DNA of zebrafish can be damaged after exposure to the above mentioned drugs. The data from the Comet Test, the Diffusion Assay and the RAPD-PCR technique were generally in agreement; these results show that all four drugs are genotoxic
Micronucleus test and comet assay for the evaluation of zebrafish genomic damage induced by erythromycin and lincomycin
No full textAn enormous quantity of pharmacologically active principles are currently being introduced into the environment, with consequent escalation of environmental problems, but only a small number of studies are focusing on an assessment of their genotoxic effects. The aim of this article is to assess the genotoxic effects of erythromycin, lincomycin, and of a combination of these two antibiotics on the genome of the zebrafish. The genotoxicity of the two antibiotics was assessed by applying the micronucleus test to erythrocytes and performing a Comet assay on erythrocytes and hepatocytes. The fish were exposed to antibiotics at different concentrations and times of exposure, under standard laboratory conditions. Depending on the different experimental conditions, erythromycin and lincomycin induced a significant increase in DNA migration (tail moment) and a significant increase in micronuleus frequency. We also conducted an analysis on the activation of repair mechanisms when the genotoxic agent was removed. Only a few of the cells displayed a decrease in damage under these test conditions. © 2011 Wiley Periodicals, Inc
A cytogenetic analysis of Gambusia holbrooki (Cyprinodontiformes, Poecilidae) from the River Sarno
No full textThe mosquitofish, Gambusia holbrooki, is one of the few teleostean fish still present in the polluted waters of the River Sarno. The specimens taken in this river had 48 chromosomes, all acrocentric, gradually decreasing in length in both sexes. However, several (12%) female plates showed a chromosome with a unilateral gap often accompanied by a chromosome number reduced to 47, due to the presence of a biarmed element derived by centric fusion of two uniarmed elements. The nuclear organizer regions (NORs) were localized on two of the smallest chromosome pairs by Ag NOR banding. C banding + DAPI revealed centromeric AT-rich heterochromatin on all elements. The results also suggest a possible mutagenic and toxic activity of the substances present in the polluted waters of the River Sarno.The mosquitofish, Gambusia holbrooki, is one of the few teleostean fish still present in the polluted waters of the River Sarno. The specimens taken in this river had 48 chromosomes, all acrocentric, gradually decreasing in length in both sexes. However, several (12%) female plates showed a chromosome with a unilateral gap often accompanied by a chromosome number reduced to 47, due to the presence of a biarmed element derived by centric fusion of two uniarmed elements. The nuclear organizer regions (NORs) were localized on two of the smallest chromosome pairs by Ag NOR banding. C banding + DAPI revealed centromeric AT-rich heterochromatin on all elements. The results also suggest a possible mutagenic and toxic activity of the substances present in the polluted waters of the River Sarno
Selachian cytogenetics: a review
No full textThe karyotype of Chondrichthyes is still the least investigated among vertebrates. Over the last 40 years, the karyotypes of 63 out of the 1100 known species (5.73%) have been described in literature, namely seven squalomorph, one squatinomorph, 20 galeomorph, 33 batoid and two holocephalian species. Generally, the diploid number ranges from a minimum of 28 to a maximum of 106 elements, with more frequent values observed between 50 and 100 chromosomes. None of the four superorders is characterized by a peculiar chromosome set or morphology; the number of uniarmed and biarmed elements is variable in all the karyotypes, and microchromosomes are often present. The general trend in all groups seems to be a progressive reduction of the telocentric chromosome number in the most specialized species, followed by the loss of the microchromosomes. Polyploidy, followed by diploidization events and Robertsonian rearrangements, might have played a key role in the karyological evolution of elasmobranch fish. Chondrichthyes have the largest genome sizes among vertebrates, with the exception of dipnoans and urodeles. In the whole class, the species examined vary greatly in size, from 3 to 34 pg/N: the lowest values have been observed in holocephalians, while galeoids and batoids have a DNA amount ranging from 5 to 15 pg/N. Squaloids show heterogeneous DNA amounts, ranging from 8 to 34 pg/N. In more recent years, karyological studies have provided new data on the characterization of selachian karyotypes by C-banding, NOR staining, restriction enzymes in situ digestion and FISH with specific DNA probes, such as telomeric and SINE sequences
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