Medical ethics: principles, persons, and perspectives: from controversy to conversation.
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Medical ethics, principles, persons, and perspectives is discussed under three headings: History, Theory, and Practice. Under Theory, the author will say something about some different approaches to the study and discussion of ethical issues in medicine--especially those based on principles, persons, or perspectives. Under Practice, the author will discuss how one perspectives based approach, hermeneutics, might help in relation first to everyday ethical issues and then to public controversies. In that context some possible advantages of moving from controversy to conversation will be explored; and that will then be illustrated with reference to a current controversy about the use of human embryos in stem cell therapy research. The paper begins with history, and it begins in the author's home city of Edinburgh. (+info)
A proposed stem cell research policy.
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The aspirations of scientists and patients for human embryonic stem cell (hESC) research in the U.S. motivate attention to the nitty-gritty of law and regulation and its confluence with such moral consensus as lies within our reach. Federal law and regulation form a tangle. Analysis yields several conclusions not widely appreciated. A legislative enactment is the rate-limiting step of federally funded research, the restriction of research imposed by the previous administration's policy as reprised in current proposals fails to achieve its objective of avoiding complicity in embryo sacrifice, the current administration's policy is another failed noncomplicity scheme under which research cannot be expanded without demolishing its putative justification, and the Food and Drug Administration has already effectively interdicted procreative cloning. While it is not plausible to deny complicity in embryo sacrifice when performing or funding hESC research, one can justify sacrifice of some embryos by an argument whose premises are consistent with a wide range of moral and religious views. This paper proposes a rule of public policy providing for the use of donated embryos barred from the womb. This rule would optimize research while manifesting its moral justification. The rule is suitable for implementation by any government that funds hESC research. The rule's justification provides a cogent argument for such incremental steps toward its implementation as become politically feasible from time to time. (+info)
Monitoring differentiation of human embryonic stem cells using real-time PCR.
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There is a general lack of rapid, sensitive, and quantitative methods for the detection of differentiating human embryonic stem cells (hESCs). Using light microscopy and immunohistochemistry, we observed that morphological changes of differentiating hESCs precede any major alterations in the expression of several commonly used hESC markers (SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, Oct-4, and Nanog). In an attempt to quantify the changes during stochastic differentiation of hESCs, we developed a robust and sensitive multi-marker quantitative real-time polymerase chain reaction (QPCR) method. To maximize the sensitivity of the method, we measured the expression of up- and downregulated genes before and after differentiation of the hESCs. Out of the 12 genes assayed, we found it clearly sufficient to determine the relative differentiation state of the cells by calculating a collective expression index based on the mRNA levels of Oct-4, Nanog, Cripto, and alpha-fetoprotein. We evaluated the method using different hESC lines maintained in either feeder-dependent or feeder-free culture conditions. The QPCR method is very flexible, and by appropriately selecting reporter genes, the method can be designed for various applications. The combination of QPCR with hESC-based technologies opens novel avenues for high-throughput analysis of hESCs in, for example, pharmacological and cytotoxicity screening. (+info)
Human ERas gene has an upstream premature polyadenylation signal that results in a truncated, noncoding transcript.
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The ERas gene is expressed in mouse embryonic stem (ES) cells and promotes their in vitro proliferation and tumorigenicity. We analyzed the expression of the human ERas gene in human ES cells by reverse transcription-polymerase chain reaction (RT-PCR) and serial analysis of gene expression but could not detect a full-length coding transcript. Sequence analysis predicted a premature polyadenylation signal for the human ERas transcript, which we confirmed by 3' RACE analysis. By RT-PCR, we identified a truncated noncoding transcript in human ES cells that is downregulated during differentiation, suggesting conserved tissue specificity of the promoter region. Previous reports and expressed sequence tag databases indicate that orthologues of this gene are expressed in other mammals, including the mouse, dog, and cow, which suggests that it became a silenced pseudogene relatively recently in mammalian evolution. In addition to the premature polyadenylation site, both the human and chimpanzee ERas genes include typical Alu-S retrotransposon insertions that could also influence expression at this locus. The lack of ERas expression in human ES cells suggests that they could have significantly different tumorigenic properties than mouse ES cells. (+info)
Generation of chromosome-specific monoclonal antibodies using in vitro-differentiated transchromosomic mouse embryonic stem cells.
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Monoclonal antibodies (MoAbs) recognizing lineage- and stage-specific human cell-surface antigens are valuable reagents for the characterization and isolation of various specialized cell populations derived from human embryonic stem cells (hESCs). In this report, we examined the use of in vitro differentiated transchromosomic mouse embryonic stem cells (TC-ESCs) as immunogens to obtain MoAbs against human cell-surface antigens. Immunization of a neural-cell population derived from differentiating human chromosome 4 and 11 TC-ESCs resulted in two chromosome-specific MoAbs, h4-neural1 and h11-neural1, respectively. The staining profiles of differentiated TC-ESCs and human embryonic carcinoma cells with these MoAbs were similar to the expression profile of nestin, a well-characterized intracellular marker for neural progenitor cells. We also described the successful purification and identification of the gene for h4-neural1 antigen (CD133, 4p15.32) with immunoaffinity chromatography. This procedure may have significant utility in generating MoAbs useful for understanding the mechanism that regulates the in vitro differentiation of hESCs. (+info)
Essential roles of sphingosine-1-phosphate and platelet-derived growth factor in the maintenance of human embryonic stem cells.
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Human embryonic stem cells (hESCs) have great potential for use in research and regenerative medicine, but very little is known about the factors that maintain these cells in the pluripotent state. We investigated the role of three major mitogenic agents present in serum--sphingosine-1-phosphate (S1P), lysophosphatidic acid (LPA), and platelet-derived growth factor (PDGF)--in maintaining hESCs. We show here that although LPA does not affect hESC growth or differentiation, coincubation of S1P and PDGF in a serum-free culture medium successfully maintains hESCs in an undifferentiated state. Our studies indicate that signaling pathways activated by tyrosine kinase receptors act synergistically with those downstream from lysophospholipid receptors to maintain hESCs in the undifferentiated state. This study is the first demonstration of a role for lysophospholipid receptor signaling in the maintenance of stem cell pluri-potentiality. (+info)
Human umbilical cord blood progenitors: the potential of these hematopoietic cells to become neural.
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The mononuclear fraction from human umbilical cord blood (HUCB) contains a significant number of stem/progenitor cells that in theory could be come any cell in the body, including neurons. Taking into consideration that transdifferentiation would be a very rare event and also knowing that overlapping genetic programs for hematopoiesis and neuropoiesis exist, we undertook a characterization of the HUCB mononuclear fraction, including analysis of cellular subpopulations and their morphology, cell viability, proliferation, and expression of neural and hematopoietic antigens. Two cell populations were apparent-adherent and floating fractions. The adherent fraction was mainly lymphocytes (~53%) expressing hematopoietic antigens. Upon replate, the floating population had many cells that expressed stem cell antigens. More of the cells in this subfraction expressed neural proteins. Neurotrophin receptors trkB and trkC were present in both cell fractions, although expression was higher in the floating fraction. Our initial characterization suggests that a subpopulation of cells exists within the HUCB mononuclear fraction that seems to have the potential to become neural cells, which could then be used in the development of cell-based therapies for brain injuries and diseases. (+info)
Parents' conceptualization of their frozen embryos complicates the disposition decision.
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OBJECTIVE: To ascertain what couples think about their embryos and how they approach making a decision about disposition in light of the fact that the disposition of unused frozen embryos has significant implications for medical research and embryo donation. DESIGN: Ethnographic qualitative interview study. SETTING: Academic research environment. PATIENT(S): Fifty-eight couples who had conceived using a donor oocyte and had at least one frozen embryo in storage. MAIN OUTCOME MEASURE(S): Tape-recorded interviews with 58 wives and 37 husbands were transcribed and analyzed for emergent themes. RESULT(S): With an average of 7.1 embryos per couple, after an average of 4.2 years of storage, 72% of couples with frozen embryos had not reached a disposition decision. Most couples had not anticipated or appreciated the consequences of having surplus embryos. Parents variously conceptualized frozen embryos as biologic tissue, living entities, "virtual" children having interests that must be considered and protected, siblings of their living children, genetic or psychological "insurance policies," and symbolic reminders of their past infertility. CONCLUSION(S): The disposition decision is not only a significant and frequently unresolved issue for couples with stored frozen embryos, but their deeply personal conceptualizations of their embryos contributes to their ambivalence, uncertainty, and difficulty in reaching a decision. (+info)