WARNOCK VERSUS POWELL (AND HARRADINE): WHEN DOES POTENTIALITY COUNT?*

Lockwood's essay is one of three in this issue of Bioethics on potentiality and its applicability to research with human embryos. (See also Richard M. Hare's "When does potentiality count? A comment on Lockwood," and Stephen Buckle's "Arguing from potential.") The author critiques the reasoning behind some of the proposals for regulating such research, particularly the recommendations of Britain's Warnock Committee and Enoch Powell's legislative response, the Unborn Children (Protection) Bill. Lockwood attempts to formulate a logically defensible and morally plausible position on potentiality, arguing that it is potential plus identity, which depends on brain development, which generates moral claims. He concludes that, while there may be practical reasons for banning embryo research after the nervous system begins to develop, it may not be morally wrong to experiment with miscarried fetuses whose brain is developing, but who are nonviable.     

WHEN DOES POTENTIALITY COUNT? A COMMENT ON LOCKWOOD

Michael Lockwood's essay, "Warnock v. Powell (and Harradine): when does potentiality count?," and Hare's response are two of three articles in this issue of Bioethics discussing potentiality and its implications for experimentation with human embryos. (See also Stephen Buckle's "Arguing from potential.") Hare responds to Lockwood's arguments on potential, an embryo's "interests," and what obligations these interests entail. In Hare's view, the interests are those of the grown person the embryo (or fetus or neonate) will become. In formulating regulations on embryo research, legislators ought to be concerned chiefly with the interests of the persons who may come into existence, grading harms differently for gametes, embryos, fetuses, and neonates, and balancing these against the expected good from the experiments.     

Two claims about potential human beings

It seems that at conception something is formed which, due to its genetic make-up, has the potentiality to develop into a full-blown human being. Many believe that in virtue of this potentiality, this organism, the human zygote or early embryo, has in instrinsic value which makes it wrong to use or produce it merely as a means to some end, e.g., some scientific end such as to produce embryonic stem cells. Against this it is here argued, first, that it does not follow from the fact that something has a potential to become a (fully developed) human being that it already is a human being (in a rudimentary sense). In fact, a human being begins to exist no earlier than a couple of weeks after conception, at the stage known as gastrulation. Thus, even granted the questionable assumption that something has instrinsic value in virtue of being a human being, the zygote will not have intrinsic value. Secondly, the value an embryo has in virtue of its potentiality to become a full-blown human being can only be instrumental, a value as a means. But of course it cannot be wrong to treat that which has merely instrumental value as a mere means or instrument to some end.     

The human embryo: a scientist's point of view

...Thus, my judgement is that a human embryo is not a human person, and so we may do experiments on it which involve killing it. But my judgement is also that a human embryo has the potential to become a human being. The consequence of this attribute is that it imposes limits on the kinds of experiments which may be performed on human embryos. It is this which sets the boundaries. Experiments which may harm the embryo while still allowing it subsequently to realise its potential, and become a person, should not be permitted. It is the potentiality of the human embryo which governs our behaviour towards it. Its potential makes it special, and radically different from any other human tissue. This potential which the early embryo has means that great respect must always be accorded it, and great thought and care must surround any dealings with it....     

The argument from potential: a reappraisal

Several criticisms of the argument from potential are reported. It is noted that such criticisms are inspired by two similarly wrong interpretations of potentiality, one confusing it with possibility and another with probability. A brief analysis of the original Aristotelian context in which the concept emerged shows that potentiality cannot be thought of as indicating the provision of some empirical facts in the future, but must rather be referred to the inherent ontological structure of the being in question. It is then argued that such an Aristotelian concept can be useful to express the dynamic structure of the person, as it must be understood according to contemporary phenomenological personalism. In the light of this philosophical tradition, the embryo can be vieewed as a being already possessing the human nature and actively developing its potential for personhood: it also follows that human nature must not be understood as a static and predetermined essence, but rather as the principle of becoming and movement toward further achievements.     

Why Eberl is wrong. Reflections on the beginning of personhood

In a paper published in Bioethics, Jason Eberl has argued that early embryos are not persons and should not be granted the status possessed by them. Eberl bases this position upon the following claims: (1) The early embryo has a passive potentiality for development into a person. (2) The early embryo has not established both 'unique genetic identity' and 'ongoing ontological identity', which are necessary conditions for ensoulment. (3) The early embryo has a low probability of developing into a more developed embryo. This paper examines these claims. I argue against (1) that a plausible view is that the early embryo has an active potentiality to grow into a more developed embryo. Against (2), I argue that neither 'unique genetic identity' nor 'ongoing ontological identity' are necessary conditions for ensoulment, and that 'ongoing ontological identity' is established between early embryos and more developed embryos. Against (3), I argue that the fact that the early embryo has a low probability of developing into a more developed embryo, if true, does not warrant the conclusion that the early embryo is not a person. If Eberl is right that the human soul is that which organises the activities of a human being and that ensouled humans are persons, embryos are persons from conception.     

Segmentation and moral status in vivo and in vitro: a scientific perspective

A basic consideration in research on human embryos is the controversy about when the embryo acquires moral status. The author refutes the contention that segmentation is the determinant of moral status. She notes that segmentation, as a stage in embryonic development, does not coincide with the development of "irreversible individuality" upon which the segmentation argument depends. Dawson also finds a lack of clarity in the meaning of "individuality." These problems, she maintains, prevent segmentation from being morally important and render the proposed 14-day limit on embryo research unnecessary. Dawson concludes that to introduce a time restriction on embryo research is premature because it is based on an inadequate philosophical argument.     

The context of embryonic development and its ethical relevance

Research on human stem cells and embryos creates ethical issues. Here I discuss ten frequently used arguments against research and point out their weaknesses. These arguments include the possessed potentiality of the embryo per se and, in contrast to other cell systems, the "slippery slope" argument, the right of disposal of parents, totipotency versus pluripotency, the burden of proof for research, natural versus artificial, and three arguments based on the precaution principle (the open biological questions, uncertainty regarding clinically applicable therapies, and the problem solving rule). I finally suggest a different answer to the ethical questions concerning research on human embryos and embryonic stem cells, which takes into consideration their biological context.     

Human embryonic stem cell research: why the discarded-created-distinction cannot be based on the potentiality argument

Discussions about the use and derivation of pluripotent human embryonic stem cells are a stumbling block in developing public policy on stem cell research. On the one hand there is a broad consensus on the benefits of these cells for science and biomedicine; on the other hand there is the controversial issue of killing human embryos. I will focus on the compromise position that accepts research on spare embryos, but not on research embryos ('discarded-created-distinction', from now on d-c-d). I will point out that this viewpoint is hard to maintain. The main focus is that the 'revealed beliefs' of its defenders are inconsistent with their 'professed beliefs', more specifically with their main argument, i.e. the potentiality argument. I will point out that (1) the defenders of d-c-d actually grant a relative moral status to the human embryo, (2) this moral status is dependent on internal and external criteria of potentiality, (3) potentiality seen as a variable value that also depends on external criteria cannot justify d-c-d, and (4) an approach to human embryonic stem cell-research that would also allow the use of research embryos is more compatible with the feelings, attitudes and values of those who currently defend d-c-d and, therefore, could lead to a broader consensus and to actions that alleviate individual human suffering.     

The effects of altering the position of cleavage planes on the process of localization of developmental potential in ctenophores.

During the transition from the four- to the eight-cell stage in ctenophore embryos, each blastomere produces one daughter cell with the potential to form comb plate cilia and one daughter cell that does not have this potential. If the second cleavage in a two-cell embryo is blocked, at the next cleavage these embryos frequently form four blastomeres which have the configuration of the blastomeres in a normal eight-cell embryo. At this division there is also a segregation of comb plate-forming potential. By compressing a two-cell embryo in a plane perpendicular to the first plane of cleavage it is possible to produce a four-cell blastomere configuration that is identical to that produced following the inhibition of the second cleavage. However, under these circumstances the segregation of comb plate potential does not occur. These results suggest that the appropriate plane of cleavage must take place for a given cleavage cycle, in order for localizations of developmental potential to be properly positioned within blastomeres.     

Use of Hybrids between Xenopus laevis and Xenopus borealis in Chimera Formation: Dorsalization of Ventral Cells

The combination of Xenopus borealis and X. laevis provides an excellent cell marking system. The potential availability of this system for chimera formation has also been suggested. However, eggs and early embryos of these species differ in size and the fusion of blastomeres of different sizez results in some disturbance in arrangement of blastomeres of a chimera. This disturbance was avoided by use of embryos from X. laevis eggs fertilized with X. borealis sperm, instead of X. borealis embryos. The cells of these hybrids could also be distinguished from the cells of X. laevis.
The fate of animal ventral cells placed in the dorsal region was followed by making a chimera by fusing a right lateral half of an 8-cell X. laevis embryo with that of an 8-cell hybrid embryo. The animal ventral cells in the "dorsal" region were found to become "dorsalized", giving rise to a lateral half of dorsal axial structures. This observation explains a previous finding that the replacement of dorsal cells by ventral ones had no effect on embryogenesis in a composite embryo.     

Artesunate and artelinic acid: association of embryotoxicity, reticulocytopenia, and delayed stimulation of hematopoiesis in pregnant rats

The artemisinin antimalarials cause embryo death and malformations in animals by killing embryonic erythroblasts. Groups of pregnant rats (N = 4) were administered 35 and 48 μmol/kg artesunate and 17.2, 28.7, 48, 96, and 191 μmol/kg artelinic acid as a single oral dose on gestational day (GD) 12. Litters were examined on GD21. The ED(50) for embryo death with artelinic acid (23.4 μmol/kg) was just slightly lower than that for decreased reticulocyte count at 24 hr postdose (33.5 μmol/kg) and both had similarly steep dose responses (maximal effects of total litter loss and ～60% decreases in reticulocyte count at 48 μmol/kg). Results with artesunate were similar. The correlation coefficient between embryo death and decreased reticulocyte count was 0.82 (p<0.01). The close relationship between embryotoxicity and reticulocytopenia is suggestive of a common mechanism-artemisinin-induced mitochondrial damage leading to cell death. At 9 days postdose, treatment with artesunate and artelinic acid also caused increases in counts of reticulocytes, lymphocytes, basophils, and monocytes (up to 3.7 ×, 1.7 ×, 4.7 ×, and 1.7 × control, respectively). This stimulation of hematopoiesis may have been mediated by the direct oxidative conversion of artesunate or artelinic acid to the artemisininyl hydroperoxide within the bone marrow cells or by an indirect increase in reactive oxygen species. The high correlation between embryotoxicity and reticulocytopenia further supports the assertion that therapeutic dosage regimens of artemisinins that cause decreases in reticulocyte count in pregnant women during the putative critical period (approximately postconception wk 3 to 9) are at risk of also causing adverse effects on the embryo.     

Features of the embryonic development of <Emphasis Type="Italic">Dienia ophrydis</Emphasis> (Orchidaceae)

A new Dienia type of the embryogenesis of orchid plants differing from the Liparis type, earlier observed for the tribe Malaxideae, has been described in Dienia ophrydis (J. Köenig) Seidenf. (Orchidaceae). The Dienia-type embryogenesis is characterized by the following features: (1) development of a single-celled suspensor formed by a cb-derivative, (2) linear arrangement of embryo cells at the tetrad stage, (3) atypical origin of some tiers, and (4) no divisions of the ci and cb cells. A hypothesis about the convergent similarity between the Dienia and Caryophyllaceae types of embryogenesis has been proposed. A number of embryo sac and embryo structures typical for D. ophrydis, including “petassum,” “fitting,” and “suspensor mantle,” have been first described. A “petassum” represents the remains of cell walls of the pollen tube and probably the filamentous apparatus of synergids sealing the micropyle side of a fertilized embryo sac. The sole suspensor cell has a special appendix (“fitting”), which connects it to the embryo. The suspensor and the fitting are surrounded by a special envelope (“suspensor mantle”), which does not cover the basal cell of the embryo (ci).     

Potentiality and human embryos

Consideration of the potentiality of human embryos to develop characteristics of personhood, such as intellect and will, has figured prominently in arguments against abortion and the use of human embryos for research. In particular, such consideration was the basis for the call of the US President's Council on Bioethics for a moratorium on stem cell research on human embryos. In this paper, I critique the concept of potentiality invoked by the Council and offer an alternative account. In contrast to the Council's view that an embryo's potentiality is determined by definition and is not affected by external conditions that may prevent certain possibilities from ever being realized, I propose an empirically grounded account of potentiality that involves an assessment of the physical and decisional conditions that may restrict an embryo's possibilities. In my view, some human embryos lack the potentiality to become a person that other human embryos have. Assuming for the sake of argument that the potential to become a person gives a being special moral status, it follows that some human embryos lack this status. This argument is then used to support Gene Outka's suggestion that it is morally permissible to experiment on 'spare' frozen embryos that are destined to be destroyed.     

Does multivariate analysis of post-thaw sperm characteristics accurately estimate in vitro fertility of boar individual ejaculates?

The objective of this study was to determine if a multivariate pattern analysis of frozen-thawed sperm characteristics of boar semen of unknown fertility, thus identifying groups of ejaculates as "good" or "bad" freezers, would estimate their fertilizing potential in an in vitro embryo production (IVP) system. Frozen-thawed spermatozoa from a single ejaculate collected from 46 boars were evaluated for sperm motility and kinematic patterns, for sperm viability and for early changes in sperm membrane stability. All data generated were used for a multivariate pattern analysis (PATN; CSIRO, Canberra, Australia) which objectively classified all ejaculates within a data set in to one of two groups, categorised as "good" (n = 25) or "bad" (n = 21) according with their freezability. In vitro matured oocytes were exposed to 2000 or 4000 frozen-thawed spermatozoa per oocyte for 6h and then cultured in embryo culture medium for either 6h (assurance of fertilization) or 7 days (to collect data on embryo development). Rates of sperm oocyte penetration and of embryo development significantly (p < 0.05) increased in a sperm:oocyte ratio-dependent manner. A similar pattern was observed when sperm characteristics were grouped. Indeed, ejaculates classified as "good" showed significantly (p < 0.05) higher rates of oocyte penetration, cleavage and of blastocyst formation than those classified as "bad". However, variation was still present among individuals (ejaculates, boars) in their ability to produce blastocysts in vitro. It is therefore concluded that despite the presence of a relationship for ejaculates with good semen quality post-thaw (thus grouped as "good") to higher IVP-results, the presence of individual variation does not allow for an accurate estimation of in vitro fertility based solely on the frozen-thawed semen quality parameters of a single ejaculate from a given boar.     

Polypeptide growth factors in animal embryogenesis

Data about polypeptide growth factors in animal cells during embryogenesis and about the sensitivity of these cells to regulatory effect of the factors have been systematically reviewed. The conclusion was drawn that they play an important role in molecular mechanisms controlling cell proliferation and differentiation at the early embryonic stages. Information has also been provided about transforming growth factors and about the products of some proto-oncogenes, which are detected in the embryonic cells in amounts comparable with those in the transformed cells. However, this does not lead to malignant growth. Moreover, microenvironment of an intact embryo exerts an antitransforming influence on tumor cells. Studies of the "normalizing" effect of the embryonic cells may help in developing new methods of suppression of the malignant growth.     

Eugenic Selection Benefits Embryos

The primary question to be addressed here is whether pre‐implantation genetic diagnosis (PGD), used for both negative and positive trait selection, benefits potential supernumerary embryos. The phrase ‘potential supernumerary embryos’ is used to indicate that PGD is typically performed on a set of embryos, only some of which will be implanted. Prior to any testing, each embryo in the set is potentially supernumerary in the sense that it may not be selected for implantation. Those embryos that are not selected, and hence destroyed or frozen, are ‘actually supernumerary’. The argument to be advanced is hypothetical: If embryos may be said to benefit or be harmed by our actions, then PGD used to select for an embryo or embryos with the highest expected Wellbeing benefits potential supernumerary embryos. The argument shows that the ‘non‐identity’ problem is not sufficient to show that eugenic selection does not benefit supernumerary embryos.     

Exploitation of genus <Emphasis Type="Italic">Rhodosporidium</Emphasis> for microbial lipid production

Oleaginous microorganisms are receiving significant attention worldwide for their utility in biodiesel production and the potentiality to produce some specialty-type lipids. There is an increasing interest in isolation/adaption of robust microbe strains and design of innovative fermentation processes to make microbial lipid production a more efficient and economically feasible bio-process. Currently, the genus Rhodosporidium has been considered an important candidate, for the reason that several strains belonging to this genus have shown excellent capabilities of lipid accumulation, broad adaptabilities to various substrates, and co-production of some carotenoids. This paper reviews the current trends in the exploitation of Rhodosporidium species for microbial lipid production, including the utilization of various (single or mixed, pure or waste-derived) substrates, progress of genetic modification and metabolic engineering, innovations in fermentation mode, lipid characterizations and their potential applications. Finally, the constraints and perspectives of cultivating Rhodosporidium species for lipid production are also discussed.     

Interrelationships among whole-body coordination, functional potentiality, and environmental adaptability

The term "adaptability" or "capacity of adaptation" is the central concept in the general advancement and promotion of research in physiological anthropology. Throughout the history of Homo sapiens, mankind has adapted itself to environmental stress. As a result, numerous physiological polymorphisms in humans are present in our planet-wide distribution. Totally regulated physiological function by integration and coordination is referred to as whole-body coordination and is associated with a high degree of adaptability in humans. Functional potentiality also affects environmental adaptability. Thus, whole-body coordination and functional potentiality are necessary for adaptation to environmental changes. There is an interrelationship among functional potentiality, whole-body coordination, physiological polymorphisms, and environmental adaptability.     

Spatial distribution of the capacity to initiate a secondary embryo in the 32-cell embryo of Xenopus laevis

To examine the spatial distribution of dorsal determinants in the early embryos of Xenopus laevis, individual cells from the 32-cell embryo were transplanted into the same tier of the ventral side of a synchronous recipient. Their abilities to initiate a secondary embryo were measured by the incidence of secondary embryos and by the length of the secondary axis relative to the primary embryo. The ability was found to be localized in all cells (A1, B1, C1, and D1) of the dorsal most column and in the vegetal cells (C2 and D2) of the dorsolateral column. Transplanted C1 (subequatorial) cells caused the highest incidence of a secondary embryo and the average relative length of the secondary embryo was also greatest. Effectiveness decreased in the order: D1, B1, D2, C2, and A1. When these results were compared with Dale and Slack's fate map of the 32-cell embryo, it was concluded that the distribution of dorsal determinants is unique and does not coincide with the prospective regions for any tissues, though it is somewhat similar to the prospective region of dorsal endoderm or notochord. From these results it seems that dorsal determinants do not determine a particular tissue in an embryo but rather the "dorsal" region of an embryo.