Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

published_or_final_version / abstract / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / Pathology / Master / Master of Medical Sciences

At the Third Turner Resource Network Symposium, a working group presented the results of collaborative discussions about the importance of autopsy in Turner syndrome (TS). Considerable gaps in understanding the causes of death in TS can only be closed by more frequent death investigations and autopsies. The presentation included an overview of autopsy methods, strategies for utilizing autopsy, and biobanking to address research questions about TS, and the role of palliative care in the context of autopsy. This review highlights strategies to promote autopsy and tissue donation, culminating with an action plan to increase autopsy rates in the TS community.

The primary aim of this study was to determine the effectiveness of array-based technology for detecting and quantifying the presence of mosaicism. This aim was achieved by studying individuals having mosaicism for Down syndrome. SNP arrays were performed on 13 samples from individuals with mosaicism for trisomy 21, 13 samples from individuals with normal chromosome 21complements (negative controls) and 5 samples from individuals with full or partial trisomy 21 (positive controls). In addition, BAC arrays were processed on 6 samples from individuals with mosaicism for trisomy 21, 3 negative controls and 1 positive control. These studies have shown that array-based technology is effective for detecting mosaicism that is present in 20% or more cells with the results being consistent for both platforms. We also demonstrated the strength of array-based technology to identify previously unrecognized chromosomal mosaicism. A second aim of this study was to gain insight regarding the effect that trisomy 21 has on telomere attrition and the frequency of chromosomal instability. This study provides the first reported measure of both chromosome-specific telomere lengths and the frequency of acquired chromosome abnormalities in trisomic cells and isogenic euploid cells obtained from the same individuals. A chromosome-specific telomere length assay was performed on lymphocytes obtained from 24 young individuals with mosaicism for Down syndrome. While differences in overall telomere signal intensities were observed between the euploid and trisomic cells within a person, strikingly similar profiles for chromosome-specific telomere intensities were observed between the cell types within a person. Analyses were also completed on lymphoblast samples obtained from 8 older individuals with mosaicism for Down syndrome, including 5 individuals without dementia and 3 individuals with dementia. In the older study subjects, a significant inverse correlation was observed between telomere length and the frequency of micronuclei, suggesting that telomeric shortening is leading to an increased frequency of chromosomal instability, possibly through dicentric chromosome formation. However, further studies of more individuals, especially additional analyses of older individuals, are needed. These future studies may help to identify genomic regions of interest and serve to inform investigators of potential candidate genes in the etiology of dementia.

L’infertilité concerne 8 à 12% des couples en âge de procréer. Face à ce problème, des prises en charge médicales peuvent être proposées comme la fécondation in vitro (FIV) et l’injection intracytoplasmique de spermatozoïde (ICSI). Toutefois, le taux d’échec de ces techniques reste relativement élevé. Dans la première partie, l’impact des facteurs maternels et paternels sur les résultats de 194 cycles de FIV et 586 cycles d’ICSI a été étudié. L’âge maternel, le nombre d’ovocytes ponctionnés et matures influencent principalement les résultats. Ni l’âge paternel ni les paramètres spermatiques (numération et mobilité) ne s’associent significativement à l’échec des techniques d’assistance médicale à la procréation (AMP). Seule la morphologie du spermatozoïde injecté a une influence sur la fécondation en ICSI. En deuxième partie, l’apoptose, la fragmentation de l’ADN et le contenu chromosomique avant et après tri cellulaire à l’aide des microbilles magnétiques ont été étudiés chez des hommes avec un taux de fragmentation de l’ADN spermatique anormal et chez des hommes porteurs d’une anomalie chromosomique constitutionnelle. Une diminution significative des spermatozoïdes apoptotiques avec un ADN fragmenté et chromosomiquement déséquilibrés a été observée. Le tri cellulaire aboutissant à une sélection de spermatozoïdes de meilleure qualité pourrait s’avérer une méthode de référence pour l’AMP. Dans une troisième partie, un protocole fiable a été élaboré pour étudier le transcriptome des spermatozoïdes. La mise au point de ces technologies permettra de mieux comprendre les causes d’échec des techniques d’AMP et ainsi améliorer leur taux de réussite. / Infertility concerns 8-12% of couples of reproductive age. Various medical treatments such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are available to address this problem. However the rate of failure of these procedures remains relatively high.In the first part of this work the impact of maternal and paternal factors on the results of 194 IVF cycles and 586 ICSI cycles was studied. Results are mainly affected by maternal age, the number of oocytes retrieved and the number of mature oocytes collected. Neither paternal age nor spermatic parameters (number and mobility) are significantly associated with the failure of Assisted Reproductive Technologies (ART). Only the morphology of the sperm injected during ICSI influences fertilization rate.In the second part of this work apoptosis, DNA fragmentation and the chromosomal content before and after cell sorting with magnetic micro beads were studied in men with an abnormal level of sperm DNA fragmentation and in men with a constitutional chromosome abnormality. A significant decrease of apoptic spermatozoa with fragmented DNA and chromosome imbalance was observed. Thus cell sorting leading to the selection of better quality spermatozoa could become a reference method for ART.In a third part of the work a reliable protocol for the study of spermatic transcriptomes is designed.The development of these technologies will lead to a better understanding of the underlying causes ofART failure and thus increase the success rate.