Biomedical subjects

Ana Vieira

Publications and source records attributed to Ana Vieira.

3 recordsLinked to original sources

PubMed2006

Gamete interaction: is it species-specific?

Reproductive isolation is pivotal to maintain species separation and it can be achieved through a plethora of mechanisms. In addition, the development of barriers to gamete interaction may drive speciation. Such barriers to interspecific gamete interaction can be prezygotic or postzygotic. Considering the great diversity in animal species, it is easy to assume that regulation of the early steps of fertilization is critical to maintain species identity. One prezygotic mechanism that is often mentioned in the literature is that gamete interaction is limited to gametes of the same species. But do gametes of all animals interact in a species-specific way? Are gamete interactions completely species-specific or perhaps just species-restricted? In species in which species-restrictions have been described, is the interspecies barrier at one major step in the fertilization process or is it a combination of partially restricted steps that together lead to a block in interspecific fertilization? Are the mechanisms used to avoid interspecific crosses different between free-spawning organisms and those with internal fertilization? This review will address these questions, focusing on prezygotic barriers, and will describe what is known about the molecular biology that may account for species-limited gamete recognition and fertilization.

Animals↗

PubMed2005

NOD2/CARD15 gene polymorphisms in Crohn's disease: a genotype-phenotype analysis in Danish and Portuguese patients and controls.

BACKGROUND: A North-South gradient in Crohn's disease (CD) implying a higher incidence in northern Europe compared to southern Europe has been established. AIMS: To investigate whether there is a difference between Denmark and Portugal in the frequency of CARD15 mutations in CD patients compared to a healthy background population and to compare genotype-phenotype relations in the two countries. METHODS: 58 Danish patients and 29 Portuguese patients with CD were matched for age, sex and disease behaviour at time of diagnosis and compared with 200 healthy Danish and Portuguese controls. Phenotypes were recorded at year of diagnosis, 3 years after diagnosis and at end of follow-up. Patients were genotyped for Arg702Trp, Gly908Arg and Leu1007InsC. RESULTS: 22% of the Danish patients vs. 9% of Danish controls compared to 21% of the Portuguese patients vs. 16% had at least one mutation. Mutation rates in Danish patients were significantly different (p=0.02) compared with Danish controls, no difference (p=0.51) was found between Portuguese patients and controls. However, a possible relationship between CD and presence of genetic mutations was found when comparing the two countries (p=0.03) using the Mantel-Haenszel test. No difference in evolution of phenotypes and the CARD15 status in CD was found during follow-up between the two matched populations. Ileal disease correlated to high occurrence of CARD15. CONCLUSION: No North-South gradient regarding occurrence of CARD15 was revealed. Although a trend towards more mutations in the Portuguese controls was seen, a relationship between CD and CARD15 mutations was observed in both countries.

Adult↗

PubMed2003

Erosion-inhibiting effect of sodium fluoride and titanium tetrafluoride treatment in vitro.

The prevention of dental erosion with fluoride is still largely unknown territory. It was the aim of this study to determine the erosion-inhibiting effect of topical neutral 1% sodium fluoride (NaF) application and an application of a 4% titanium tetrafluoride (TiF4) solution compared with no treatment. Ten bovine incisors were selected and three enamel samples prepared from each tooth. One sample from each tooth was assigned to one of three experimental groups. The experimental treatments were: no fluoride application (control); 4 min application of neutral 1% NaF gel; and 4 min application of 4% TiF4 solution. All of the specimens were repeatedly exposed to 50 mm citric acid solution containing 0.4 mm CaCl2, and 2.2 mm KH2PO4 at pH 3.0 over four consecutive days. The acid exposure was performed in intervals and the intensity was increased over the days of the experiment. Enamel dissolution was determined by calcium content measurement of the acid solution after exposure, using atomic absorption spectroscopy. A statistically significant erosion-inhibiting effect was found for both NaF and TiF4 treatments compared with the control group from an erosion exposure time of 3 min. The reduction of calcium loss, however, was higher for the TiF4-treated specimens than the NaF-treated. From 16 min of erosion exposure, the erosion-inhibiting effect was significantly stronger in the TiF4 than the NaF group. The relative reduction of calcium loss compared with the control group remained stable for the TiF4 group, whereas for the NaF group the relative reduction decreased with cumulative erosion time. It is concluded that topical TiF4 application provides a potential treatment option in erosion prevention.

Analysis of Variance↗