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Alan Trounson

Publications and source records attributed to Alan Trounson.

25 records · Page 2Linked to original sources
PubMed2002

Human embryonic stem cells: mother of all cell and tissue types.

Pluripotential embryonic stem (ES) cells have been derived very efficiently from spare human embryos produced by IVF and grown in culture to the nascent blastocyst stage. The inner cell mass (ICM) is isolated by immunosurgery and grown on selected embryonic fibroblast monolayer cultures. ICM cells lose their memory for axis during formation of ES cell colonies and are then unable to integrate tissue formation with a body plan. ES cells form teratomas in vivo with cells and tissues representative of the three major embryonic lineages (ectoderm, mesoderm, endoderm). The ES cells are continuously renewable and can be directed to differentiate into early progenitors of neural stem cells (Noggin cells) and from there into mature neurons and glia (astrocytes and oligodendrocytes). The neural stem cells formed from human ES cells repopulate the brains of newborn mice when injected into the lateral cerebral ventricles, forming astrocytes dominantly in the parenchyma. The human neural cells can be observed migrating from the subventricular areas along the rostral migratory stream. Human neurons can be found in the olfactory bulb. Human ES cells can also be directed into cardiomyocytes when co-cultured with visceral endoderm-like cells (END-2). These observations provide further scope to explore stem cell therapies, gene therapies and drug discovery. For compatible transplantation, ES may need to be derived with a range of HLA types or by nuclear transplantation or stem cell fusion.

Animals↗
PubMed2002

Technical advances and pitfalls on the way to human cloning.

There exists a widespread consensus that the cloning of human beings to term would be detrimental to both the mother and child and of little value to society. However, the ambition of a few organisations and the recent advances in cellular and molecular technologies that led to the cloning of Dolly the sheep, for example, have meant that such a procedure will be possible if not illegal in the near future. The science associated with the cloning technologies practiced in other mammalian species reported to date provide important advances in our understanding of how cells function during early developmental processes and commit themselves to specific developmental pathways. However, many technological insufficiencies remain. Both technological advances and several of the associated insufficiencies are outlined in this review.

Animals↗
PubMed2001

Fertilization of mouse oocytes using somatic cells as male germ cells.

Female and male mouse somatic cells were injected into mouse F(1) oocytes. The cells used included cumulus cells (female) and muscle derived fibroblasts (male). The ability of the cells to fertilize oocytes and support embryonic development was examined. Following activation of the injected oocytes, two second polar bodies were extruded and two pronuclei were formed, one derived from the oocyte chromosomes and the other from the somatic cell chromosomes in a similar way to that observed following fertilization with secondary spermatocytes. Both second polar bodies contained DNA. The fertilization rates by cumulus cells were 10-29%. This was dependent on the artificial activation protocol and on the age of the oocytes. Older oocytes recovered 16-17 h after human chorionic gonadotrophin (HCG) injection were more likely to produce two second polar bodies and two pronuclei than young oocytes which were retrieved at 13-14 h after HCG injection (P < 0.01). The fertilization rates with fibroblasts were 29% using the most effective activation regime and aged oocytes. Most (80-90%) of the 'zygotes' produced by somatic cells cleaved to two cells in culture and ~50% reached the morula stage. However, the developmental competence of the embryos to reach blastocysts was limited. The present study demonstrates that mouse somatic cells undergo haploidization when injected into metaphase II oocytes, fertilize oocytes as diploid male germ cells and support preimplantation development to a degree.

Journal Article↗
PubMedDate not supplied

The fine structure of human embryonic stem cells.

The fine structure of human embryonic stem (ES) cell colonies was analysed by transmission electron microscopy (TEM) after 35 passages of in-vitro culture. Most cells formed compact, saucer-shaped colonies with epithelioid cells on the periphery and polygonal cells within the colony. Three morphological types of cells were identified based on their fine structure: undifferentiated cells resembling inner cell mass (ICM) cells of blastocysts; protein-synthesizing cells at the onset of cellular differentiation; and compact masses of secretory cells resembling unicellular goblet cells of the intestine. The predominant cell type was the undifferentiated ES cells resembling ICM cells of blastocysts. These cells had large nuclei containing reticulated nucleoli, well-developed rough endoplasmic reticulum (RER), Golgi complexes, elongated tubular mitochondria, lysosomes and typical centrosomes with centrioles associated with microtubules and microfilaments, organizing the cytoskeleton. Some ES cells have very large nuclei and scanty cytoplasms with fewer organelles. The isolated or attached protein-synthesizing cells at the onset of differentiation had extensive RER and large Golgi complexes. The morphologically differentiated cells formed compact colonies and resembled goblet-like cells in microstructure. They had RER and large Golgi complexes associated with secretory vesicles. The epithelioid cells at the periphery were columnar and largely polarized by centrosomes associated with Golgi complexes. Epithelioid cells in all three categories had specialized cell junctions (desmosomes), anchored by tonofilaments, and surface blebs. Isolated cells were seen on the surface, towards the centre of the colony, and their free surfaces had microvilli and larger blebs. Approximately 3-5% of all cells were mitotic, with typical bipolar spindles organized by centrosomes, pivotally located at the poles, and appeared to resemble typical somatic cells.

Blastocyst↗
PubMedDate not supplied

Selected genetic factors associated with male infertility.

Studies into the mechanisms underlying spermatogenesis, the process by which spermatogonia undergo meiosis to become spermatozoa, have identified a number of genetic determinants of male infertility. Indeed, a more comprehensive knowledge of the genetic regulation of spermatogenesis has alleviated the dependence on the use of idiopathic infertility as a classification for sterile men for whom a cause for their infertility is unknown, as genetic factors become more accountable for this phenotype. This review focuses on selected areas implicated in male infertility including: (i) autosomal and sex chromosomal abnormalities; (ii) genetic disorders associated with impaired gonadotrophin secretion or action; (iii) microdeletions within regions of the Y-chromosome containing candidate gene families for spermatogenesis; (iv) the genetic nexus between cystic fibrosis and congenital bilateral absence of the vas deferens; and (v) insights into human infertility as gleaned from animal studies into mechanisms involving the Bcl-2 family of apoptosis regulators and the interaction between the c-kit encoded tyrosine kinase receptor and its ligand, stem cell factor. As significant advances continue to further knowledge of the genetic basis of male infertility, such as those leading to an understanding of the aforementioned areas, greater progress can be made to rectify or at least ameliorate social stigmas associated with sterility.

Animals↗