Differences in mitochondrial and nuclear DNA status of high-density and low-density sperm fractions after density centrifugation preparation

Background: In order to isolate the â??bestâ?? sperm for assisted conception a discontinuous two-step density gradient centrifugation is usually employed. This technique is known to isolate a subpopulation with good motility, morphology and nuclear DNA (nDNA) integrity. As yet its ability to isolate sperm with unfragmented mitochondrial DNA (mtDNA) is unknown. Methods: Semen was obtained from men (n=28) attending our Regional Fertility Centre for infertility investigations. We employed a modified long polymerase chain reaction to study mtDNA and a modified alkaline Comet assay to determine nDNA fragmentation. Results: The high- density fraction displayed significantly more wild type mtDNA (75% of samples) than that of the low- density fraction (25% of samples). In the high-density fraction, there was a higher incidence of single, rather than double or multiple deletions and the deletions were predominantly small scale (0.1-4.0kb). There was a strong correlation between nDNA fragmentation, the number of mtDNA deletions (r=0.7, p

The European Convention on Human Rights after Enlargement

The Council of Europe has dramatically enlarged its membership over the past decade, encompassing the vast majority of the formerly Communist states of Central and Eastern Europe. With this dramatic enlargement, the Council has sought to secure its place in the complex institutional architecture of post-Cold War Europe, building on its traditional strengths in the promotion of democratic governance and human rights. Yet, both inside and outside the organisation, voices have been raised to suggest that the Council has lowered its admission standards in a manner which risks compromising the legitimacy of the European Convention on Human Rights. Against the background of these ongoing controversies, this article assesses the impact of enlargement on the European human rights system. Focusing on the composition of the European Court of Human Rights and the initial pattern of cases from the Central and East European member states, it is demonstrated that the short-term impact of enlargement has been quite limited. Nevertheless, it is clear that the Court will face major new challenges over the coming years. In part, the Court will have to assume the role of an adjudicator of transition. More generally, there will also be mounting pressures for it to (re)cast itself more clearly as a European constitutional court.

Analysing spatio-temporal change by use of national historical Geographical Information Systems: Population change during and after the Great Irish Famine

Several countries have made large investments in building historical Geographical Information Systems (GIS) databases containing census and other quantitative statistics over long periods of time. Making good use of these databases requires approaches that explore spatial and temporal change.

Assessment of DNA integrity and morphology of ejaculated sperm from fertile and infertile men before and after cryopreservation

Cryopreservation of human spermatozoa is extensively used in artifical insemination and IVF programmes. Despite various advances in cryopreservation methodology, the recovery rate of functional post thaw spermatozoa remains mediocre, with sperm motility being significantly decreased after freezing. The aim of this study was to investigate the effects of cryopreservation on both DNA integrity and morphology of spermatozoa from fertile and infertile men. Semen samples were obtained from 17 fertile men and 40 infertile men. All samples were prepared by discontinuous Percoll density centrifugation ( 95.0:47.5). Samples were divided into aliquots to allow direct comparison of fresh and frozen spermatozoa from the same ejaculate. Aliquots for cryopreservation were mixed with a commercial cryoprotectant and frozen by static phase vapour cooling before plunging into liquid nitrogen. Thawing was carried out slowly at room temperature. Sperm DNA integrity was determined using a modified alkaline single cell gel electrophoresis ( comet ) assay and sperm morphology analysed using the Tygerberg criteria. DNA of semen and prepared sperm from fertile men was found to be unaffected by cryopreservation. In marked contrast, spermatozoa from infertile men were significantly damaged by freeze- thawing. Cryopreservation had a detrimental effect on morphology of semen and prepared sperm from fertile and infertile men.