This paper argues that embryonic development is best understood through the lens of process philosophy rather than traditional substance metaphysics. Drawing on both contemporary developmental biology and process thought, I demonstrate how key phenomena in embryogenesis-including morphogenesis, cellular differentiation, and organismal integration-align naturally with process-philosophical principles. Through critical engagement with major figures in developmental biology and philosophy of biology, including Turing's mathematical theory of morphogenesis and autopoietic approaches to biological organization, I show how persistent difficulties in developmental biology (...) stem from implicit substance-metaphysical assumptions and demonstrate how a process framework better captures the dynamic, relational nature of development. Furthermore, I argue that this perspective provides novel insights into emergence in biological systems while resolving longstanding theoretical difficulties in developmental biology. This theoretical framework has important implications for both biological understanding and experimental practice. (shrink)

Modern synthesis proposes that evolution is a random process, without directionality or purpose. This claim would be in conflict with the teleological proposal of the fifth way of St. Thomas Aquinas, who in his first premise asserts the existence of natural bodies that act for a purpose. This paper discusses theoretical, conceptual arguments, and especially empirical evidence, to show that the morphogenetic processes occurring during embryonic development do indeed have directionality and purpose. Based on this, a scientific teleology (...) is defended, to provide at least minimal support for the empirical validity of the first way. (shrink)

The successes of molecular developmental biology over the last ten years have been particularly impressive in those directions favored by its major paradigms. New technologies have both guided and been guided by the progress of the field. I review briefly some of the major insights into embryonic development that have derived from research in four specific areas: early embryogenesis of various forms; “pattern formation”; evolutionary conservation of regulatory elements; and spatial mechanisms of gene regulation. There remain many major (...) problem areas, some of which may require new orientations to solve. (shrink)

Reproductive diseases are a long‐standing problem and have become more common in the world. Currently, 15% of the world's population suffers from infertility, and half of them are women. Maturation of oocytes, successful fertilization, and high‐quality embryos are prerequisites for pregnancy. With the development of assisted reproductive technology and advanced genetic assays, we have found that infertility in many young female patients is caused by mutations in various developmental regulators. These pathogenic factors may result in impediment of oocyte maturation, (...) failure of fertilization or early embryonic development arrest. In this review, we categorize these clinically‐identified, mutated genetic factors by their molecular characteristics: nuclear factors (PALT2, TRIP13, WEE2, TBPL2, REC114, MEI1 and CDC20), cytoplasmic factors (TLE6, PADI6, NLRP2/5, FBXO43, MOS and BTG4), a factor unique to primates (TUBB8), cell membrane factor (PANX1), and zona pellucida factors (ZP1‐3). We compared discrepancies observed in phenotypes between human and mouse models to provide clues for clinical diagnosis and treatment of related reproductive diseases. (shrink)

Chromosomes are not randomly packed and positioned into the nucleus but folded in higher‐order chromatin structures with defined functions. However, the genome of a fertilized embryo undergoes a dramatic epigenetic reprogramming characterized by extensive chromatin relaxation and the lack of a defined three‐dimensional structure. This reprogramming is followed by a slow genome refolding that gradually strengthens the chromatin architecture during preimplantation development. Interestingly, genome refolding during early development coincides with a progressive loss of developmental potential suggesting a link (...) between chromatin organization and cell plasticity. In agreement, loss of chromatin architecture upon depletion of the insulator transcription factor CTCF in embryonic stem cells led to the upregulation of the transcriptional program found in totipotent cells of the embryo, those with the highest developmental potential. This essay will discuss the impact of genome folding in controlling the expression of transcriptional programs involved in early development and their plastic‐associated features. (shrink)

Two aspects of the chromatin repeat length (r t) are discussed: (i) Why is r t, longer for slowly dividing cells than in rapidly dividing cells?, and (ii) Why is the temporal evolution of r ta decreasing function of time (t) in mammalian cortical neurons, whereas it is an increasing function of t for granule cells around the time of birth? These questions are discussed in terms of a hypothesis which assumes a correlation between deoxyribonucleic acid (DNA) packaging, transcription, and (...) replication. (shrink)

The precocious induction in vivo and in culture of insect and amphibian metamorphosis by exogenous ecdysteroids and thyroid hormones, and its retardation or inhibition by juvenile hormone and prolactin, respectively, has allowed the analysis of such diverse processes of post‐embryonic development as morphogenesis, tissue remodelling, functional reorganization, and programmed cell death. Metamorphosis in vertebrates also shares many similarities with mammalian development in the late foetal and perinatal period. This review describes the regulation of expression of some of (...) the ‘adult’ gene products during metamorphosis in invertebrates and vertebrates. Recent studies on metamorphosis have revealed the important role played by auto‐induction of hormone receptor genes, based on which a model will be presented to explain the activation of ‘downstream’ genes which give rise to the adult phenotype. It will also be argued that metamorphosis is an ideal model for analyzing some of the major mechanisms governing post‐embryonic development. (shrink)

During development some cells are migratory whilst others are stationary. However, the same cell may change its behaviour depending upon its environment. Recent evidence has implicated the extracellular matrix protein fibronectin in the regulation of migratory behaviour. As the structure of this molecule becomes elucidated, it is also becoming possible to interpret this regulation in precise molecular terms.

Possible etiological factors of congenital malformations as well as of human trisomies are considered in the framework of the repressor hypothesis. In this approach gene expression is envisaged from the point of view of the functional variations of the total activation energy for normal gene expression in homeostatic equilibrium. We restrict our attention to variations of the total activation energy under the effect of temperature gradients. We discuss the evidence that hyperthermia may be an etiological factor for trisomies in humans.

Arthrogryposis multiplex congenita (AMC) is a heterogeneous syndrome where multiple joints have reduced range of motion due to contracture formation prior to birth. A common cause of AMC is reduced embryonic movement in utero. This reduction in embryonic movement can perturb molecular mechanisms and signaling pathways involved in the formation of joints during development. The absence of mechanical stimuli can impair joint cavitation, resulting in joint fusion, and ultimately eliminate function. In turn, mechanical stimuli are critical for (...) proper joint formation during development and for mitigating AMC. Studies in experimental animal models have provided a greater understanding on the molecular pathophysiology of congenital contracture formation as a consequence of embryonic immobilization. Elucidation of how the mechanical signaling environment is transduced to initiate a biological response will be necessary to gain a deeper understanding of how mechanical stimuli are intertwined in the molecular regulation of joint development. (shrink)

Despite decades of philosophical and scientific investigation, no consensus has emerged on when human consciousness begins during embryonic development. This paper offers a novel framework that integrates developmental neurobiology with a structural philosophy of judgement. Drawing on the Judgemental Triad and the Pre-Judgemental Field, we identify six stages of ontological and neurobiological progression toward consciousness. We argue that consciousness first becomes structurally possible between gestational weeks 23–26, when affective sensitivity becomes recursively structured through cortical and subcortical integration. This (...) approach offers the first ontologically grounded, biologically consistent model for determining the threshold of conscious emergence. (shrink)

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. (shrink)

Endochondral bone formation can take place in the embryo, during fracture healing, or in postnatal animals after induction by implanted demineralized bone matrix. This matrix‐induced bone formation recapitulates the embryonic sequence of bone formation morphologically and biochemically. The steps in bone formation in both systems include differentiation of cartilage from mesenchyme, cartilage maturation, invasion of the cartilage by blood vessels and marrow precursors, and formation of bone and bone marrow. Recently, bone inductive molecules from demineralized bone matrix have been (...) purified, sequenced and produced as recombinant proteins. While there are similarities between bone development in the embryo and that after induction by these purified molecules, the molecules responsible for bone induction in the embryo have not yet been defined. Because of similarities between the two methods of bone formation, studies of Bone induction by demineralized bone matrix may help to elucidate mechanisms of embryonic bone induction. (shrink)

One of the earliest and most‐fundamental pattern‐ formation events in embryonic development is endoderm and mesoderm specification. In sea urchin embryos, this process begins with blimp1 and wnt8 gene expression at the vegetal pole as soon as embryonic transcription begins. Shortly afterwards, wnt8/blimp1 expression spreads to the adjacent ring of mesoderm progenitor cells and is extinguished in the vegetal‐most cells. A little later, the ring of wnt8/blimp1 activity moves out of the mesoderm progenitors and into the neighboring (...) endoderm cells. Remarkably, this moving ring of gene expression has now been shown to be controlled entirely by transcriptional cis‐regulatory logic.1. BioEssays 30:412–417, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Since their derivation, human embryonic stem (hES) cells have been used for a variety of applications including developmental biology, pathology, chemical biology, genomics, and proteomics. However, their most important potential application is the generation of cells and tissues, which can be used for cell‐based therapies. One of the main drawbacks of hES cell culture is that they are particularly sensitive to dissociation, which is required for passaging, expansion, cryopreservation, and other applications. Recently, it has been discovered that an inhibitor (...) of Rho kinase (ROCKi; Y‐27632) increases the survival rate of dissociated, single hES cells. This breakthrough has allowed new methods in hES cell culture to be developed, with the promise of increasing hES cell numbers into the realm of clinical relevance. In our studies demonstrating that ROCKi dramatically increases hES cell cryopreservation efficiency, we have observed that ROCKi treatment does not decrease hES cell's susceptibility to apoptosis. Rather, we hypothesize that ROCKi treatment desensitizes single hES cells to their environment reducing the odds that individual cells will undergo anoikis. (shrink)

Human embryonic moral status in the embryo debate in the Indian religious school of thoughts is a challenging issue. The paper tries to figure out whether ontological status implies moral status of embryo. Consciousness is an important determinant of animation of human embryo. In this paper an attempt had been made to understand the concept of man and soul in the Hindu philosophical thought. In the process we would also make a critical review of embryology in the Hindu philosophical (...) thought. The study would adopt a conceptual elucidation of morality. The paper made an elaborative study of Puruṣa as found in the Saṃkhya Philosophy and the study of consciousness and animation would try to resolve the related question, when does life begin to have that value? Embryo-protectionist regards embryos as a potential person. The Gita says the human person is individual self-called āttmā, whose nature is of pure consciousness, Brahman/Puruṣa. Consciousness constitutes the essentiality of individual Self. Human embryo developments are elaborately studied in the Yajñavalkya Smṛti, Garbha Upaniṣad, and Suśruta Saṃhitā. The self that remain latent in the embryo gets impetus with the association of consciousness until then it cannot be a human personality. In Hinduism sanctity of life gets combined with autonomy and self-determination. The sanctity of life applies both to the fetus as well as to the overall welfare of the society. The embryo being in an interim stage and the soul not being destroyed upon body annihilation, it may be claimed that since destruction or annihilation of the physical form does not destroy the soul, beneficial embryo research should thus not be abhorrent. The Hindu ethics as examined here precludes the consideration of the situation at hand, and causing the least harm and work according to one’s dharma. (shrink)

The recent success in generating live offspring from embryonic stem cell (ESC) –derived gametes in mice sparked visions of growing tailor-made sperm for men faced with infertility. However, although this development will almost certainly lead to new insights into the processes underlying spermatogenesis and thus in the possible causes of male infertility, it is less certain if deriving sperm from ES cells, which are in turn derived from a sterile man, can make someone a genetic parent. As the (...) gap between newly envisioned reproductive technologies and natural reproduction widens, the question thus needs to be asked if these possible therapies still lead to genetic parenthood. (shrink)

The relationship of embryonal carcinoma (EC) cells, the stem cells of germ cell‐ or embryo‐derived teratocarcinoma tumors, to early embryonic cells came under intense scrutiny in the early 1970s when mouse chimeras were produced between EC cells and embryos. These chimeras raised tantalizing possibilities and high hopes for different areas of research. The normalization of EC cells by the embryo lent validity to their use as in vitro models for embryogenesis and indicated that they might reveal information about the (...) relationship between malignancy and differentiation. Chimeras also showed the way for the potential introduction of genes, selected in EC cells in vitro, into the germ line of mice. Although EC cells provided material for the elucidation of early embryonic events and stimulated many studies of early molecular differentiation, after years of intense scrutiny, they fell short as the means of genetic manipulation of the germ line, although arguably they pointed the way to the development of embryonic stem (ES) cells that eventually fulfilled this goal. (shrink)

Mouse embryonic stem cell lines offer an attractive route for introducing rare genetic alternations into the gene pool since the cells can be pre‐screened in culture and the mutations then transmitted into the germline through chimera production. Two applications of this technique seem ideally suited for a genetic analysis of development are enhancer and gene trap screens for loci expressed during gastrulation and production of targeted mutations using homologous recombination. These approaches should greatly increase the number of mouse (...) developmental mutants available and help to elucidate the genetic hierarchy controlling embryogenesis. (shrink)

While much has been written on the moral and metaphysical status of fetuses in Christian bioethics, little thought has been given to how we might characterize the afterlives of the unborn, especially of those human biological individuals who die before even developing a body that could theoretically be resurrected. In this paper, I therefore undertake an examination of questions surrounding the afterlife, specifically as it relates to early pregnancy loss. I first lay out what I call the “problem of weird (...) heavens” that arises when we consider that significantly more unborn human beings have died than have been born in the history of humankind. I then go on to consider questions surrounding both the soteriological status of the embryo and the status of any resurrected “body” it might have. I conclude with the germs of an alternative approach mirrored on the idea of embryonic resorption and mystical union. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Kennedy Institute of Ethics Journal 14.1 (2004) 47-54 [Access article in PDF] Ethical Guidelines for Human Embryonic Stem Cell Research*(A Recommended Manuscript) Adopted on 16 October 2001Revised on 20 August 2002 Ethics Committee of the Chinese National Human Genome Center at Shanghai, Shanghai 201203 Human embryonic stem cell (ES) research is a great project in the frontier of biomedical science for the twenty-first century. Be- cause the (...) research involves the use of human embryos, it triggers serious debate on ethical issues. Opponents consider the embryo to be an early form of human life that should be respected and not destroyed. However, the majority of scientists support embryonic stem cell research, believing that it offers good prospects for the treatment of diseases that have remained incurable until now and so will benefit humankind. The Ethics Committee of the Department of Ethical, Legal, and Social Implications of the Chinese National Human Genome Center at Shanghai seriously discussed the ethical debate initiated by embryonic stem cell research. We concluded that we should support the scientists of our country in actively carrying out human embryonic stem cell research for the noble cause of "medicine being a beneficent art." For the healthy and orderly development of human embryonic stem cell research in our country, we put forward the following recommended Ethical Guidelines for Human Embryonic Stem Cell Research as a reference for leaders, administrative departments, and related scientists. Preface Article 1. Human embryonic stem cells are the primitive cells that play the main role in the growth and development of a human body. These [End Page 47] primitive cells have the potential for infinite proliferation, self-renewal, and multi-directional differentiation. If scientists can discover the mechanism of differentiation of human embryonic stem cells, it will be possible to induce differentiation of human embryonic stem cells to form various types of human cells for clinical cell therapy. If human embryonic stem cell research can be integrated with modern biomedical engineering techniques, it also will be possible to make repair and replacement of human tissues and organs a reality. Article 2. There are two ways to classify human embryonic stem cells. One way is to classify them according to their potential for differentiation. There could be three kinds of stem cells: totipotent stem cells, pluripotent stem cells, and unipotent stem cells.A totipotent stem cell has the potential to develop into a whole individual. It can differentiate into the more than 200 cell types in the whole body, construct any tissue or organ of the body, and finally develop into a whole individual. The fertilized egg and the cleavage cells at the very early stage of embryonic development are totipotent stem cells.A pluripotent stem cell has the potential to differentiate into many cell types derived from the three embryonic layers. However, it has lost the capacity to develop into a complete organism.A unipotent stem cell is derived from the further differentiation of the pluripotent stem cell. It can differentiate only into one cell type such as a hematopoietic stem cell, neural stem cell, and others.The other way is to classify human stem cells according to their source. There could be two kinds of human stem cells: embryonic stem cells and tissue stem cells (also called adult stem cells). The former involves experimentation with embryos, which has serious ethical implications. Ethical issues associated with the latter are mainly expressed in the various opinions regarding the allocation of health resources. Article 3. Human embryonic stem cells are the group of cells called the blastocyst inner cell mass during the early stage of embryonic development. They are the main source of totipotent stem cells, and hence the focal and hot point in stem cell research. Studies on the clinical application of embryonic stem cells probably will involve use of the somatic cell nucleus transfer (SCNT) technique, which destroys the early human embryo. At present, the ethical and moral debate is very serious in human embryonic stem cell research regarding whether the research will develop... (shrink)

The differentiation of mammalian neurons during development is a highly complex process involving regulation and coordination of gene expression at multiple steps. The P19 mouse embryonal carcinoma cell line is a suitable model system with which to analyze regulation of neuronal differentiation. These multipotential cells can be maintained and propagated in tissue culture in an undifferentiated state. Exposure of aggregated P19 cells to retinoic acid results in the differentiation of cells with many fundamental phenotypes of mammalian neurons. Undifferentiated P19 (...) cells are amenable to genetic manipulations such as transfection and establishment of stable clonal cell lines expressing introduced genes. Proteins that play a key role in the neuronal differentiation of P19 cells are beginning to be identified. These include retinoic acid receptors, the epidermal growth factor receptor and the transcription factors Oct‐3 and Brn‐2. The biological and technical advantages of this system should facilitate deeper analysis of the activities of proteins that play a role in neuronal differentiation. (shrink)

While some people claim that the present disagreement over embryonic stem cell research cannot be resolved, others argue that developing transparency and trust are key elements that could resolve the existing disagreements over such research. This paper reveals that transparency is not necessarily a requirement for advancing ES cell research, since in Israel, for instance, there is no transparency, and research nevertheless flourishes. Moreover, trust is not independent of cultural values and religious beliefs. Because of these beliefs, the environment (...) in Israel for ES cell research has been pragmatic and liberal. The Israeli case illustrates the key role that culture and religion can play in biomedical research; it also suggests that as far as cultural values or religious beliefs of people in Western countries strongly oppose research on embryonic tissue, it would be very difficult, if not impossible, to overcome the disagreements. (shrink)

Embryonic stem cell research holds great promise for biomedical research, but involves the destruction of human embryos. Katrien Devolder explores the tension between the view that embryos should never be deliberately harmed, and the view that such research must go forward. She provides an in-depth analysis of major attempts to resolve the problem.

The developing mammalian heart responds to a variety of conditions, including changes in nutrient availability, blood oxygenation, hemodynamics, or tissue homeostasis, with impressive growth plasticity. This ensures the formation of a functional and normal sized organ by birth. During embryonic and fetal development the heart is exposed to various physiological and potentially pathological changes in the intrauterine environment which dramatically impact on normal cardiac function, tissue composition, and morphology. This paper summarizes the mechanisms employed by the embryonic (...) and fetal heart to adapt to various intrauterine challenges to prevent or minimize postnatal consequences of impaired cardiac development. Future investigations of this growth plasticity might lead to new therapeutic strategies for the prevention of cardiac disease in postnatal life. (shrink)

BackgroundHuman embryonic stem cells (hESC) as a source for the development of advanced therapy medicinal products are considered for treatment of Parkinson’s disease (PD). Research has shown promising results and opened an avenue of great importance for patients who currently lack a disease modifying therapy. The use of hESC has given rise to moral concerns and been the focus of often heated debates on the moral status of human embryos. Approval for marketing is still pending.ObjectiveTo Investigate the perspectives (...) and concerns of patients with PD, patients being the directly concerned stakeholders in the ethical discussion.MethodsQualitative semi-structured interviews related to this new therapy in seventeen patients from two Swedish cities.ResultsThe participants expressed various interests related to the use of human embryos for development of medicinal therapies; however, overall, they were positive towards the use of hESC for treatment of PD. It was deemed important that the donating woman or couple made the choice to donate embryos voluntarily. Furthermore, there were concerns that the industry does not always prioritise the patient over profit; thus, transparency was seen as important. (shrink)

A new human life comes into being not when there is mere cellular life in a human embryo, but when the newly developing body organs and systems begin to function as a whole, the author argues. This is symmetrical with the dealth of an existing human life, which occurs when its organs and systems have permanently ceased to function as a whole. Thus a new human life cannot begin until the development of a functioning brain which has begun to (...) co-ordinate and organise the activities of the body as a whole. (shrink)

When in doubt, for the embryo. New arguments on the moral status of human embryos. - In the first part of our essay we distinguish the philosophical from the legal and political level of the embryo debate and describe our indirect justification strategy. It consists in renouncing a determination of the dignity-giving φ-properties and instead starting from premises that are undoubted by all discussion partners. In the second part we reconstruct and criticize the species, continuum, identity and potentiality arguments. The (...) species argument only has a certain plausibility, if at all, as a critical argument. From the continuum argument and identity argument we take over the idea of numerical identity (NI) and link it with the core idea of the potentiality argument (P). So we come to the NIP argument: (NIP) (1) Every living human body that is the bearer of (or has) potential φ-properties has dignity. (2) Every viable human embryo is a living human body that is the bearer of (or has) potential φ properties. Therefore, (3) Every viable human embryo has dignity. Reversibly comatose people and newborns are protected because they have the potential to have actual personal characteristics in the future; our thesis is that embryos that are capable of development also have the same potential in moral terms. The basic idea of numerical identity, with which we support the second premise, is that every human being, from embryonic existence to adulthood, forms a physical unity. In a detailed part, we deal with the crown princess, gametes, parthenogenesis, somatic cell, pronuclear stage, biological heteronome early embryo, multiple, fusion, Siamese twin, hydatidiform mole and finally trophoblast problems. In a third part, the indirect argument is supplemented by a metatheoretical cautionary argument. It states that in situations where there is doubt as to whether a being falls within the scope of a moral norm, but there are sufficiently strong reasons for this subsumption, it must be assumed that this is the case if the contrary assumption and the positive effects it may have are in no acceptable proportion to the moral harm that would result if that subsumption were not made. The main result of our considerations is therefore: When in doubt, for the embryo. (shrink)

This book provides a comprehensive overview of corporate social responsibility and its development in Africa. It provides in-depth studies on 11 sub-Saharan countries, demonstrating that corporate social responsibility is forming and going through different stages of metamorphosis in the continent. Though corporate and individual attitudes towards sustainability in Africa still leave a lot to be desired, this book showcases how things are rapidly changing for the better in this regard. It demonstrates and provides evidence for the fact that corporate (...) social responsibility contributes significantly to the way sub-Saharan African economies are being transformed, with service sectors expanding, commercial activities diversifying and industrial bases growing through the initiatives of small, medium and large organizations and innovators supported by widespread higher-education program rollouts. The book highlights how progressive and wide-ranging CSR approaches have emerged, and how much they differ from the obsolete approaches of the past, which promulgated negative stereotypes, marginalized communities and positioned them as victims or beneficiaries of development. (shrink)

Restrictions on research on therapeutic cloning are questionable as they inhibit the development of a technique which holds promise for succesful application of pluripotent stem cells in clinical treatment of severe diseases. It is argued in this article that the ethical concerns are less problematic using therapeutic cloning compared with using fertilised eggs as the source for stem cells. The moral status of an enucleated egg cell transplanted with a somatic cell nucleus is found to be more clearly not (...) equivalent to that of a human being. Based on ethical considerations alone, research into therapeutic cloning should be encouraged in order to develop therapeutic applications of stem cells. (shrink)

Combining human embryonic stem cells with SCNT has been a gold standard of stem cell research. Adding a particular individual's genes to pluripotent stem cells might lead to the development of personalized tissue repair or replacement. Enthusiasm for human embryonic stem cell research had flagged in recent years due to controversy over the moral status of in vitro embryos, scientific misconduct by researcher Woo Suk Hwang, and the discovery that induced pluripotent stem cells could be produced from (...) somatic cells. Energy shifted to research on somatic cells, but three successes in the United States during 2013 and 2014 may reinvigorate embryonic stem cell research. (shrink)

Cytoskeletal organization in embryonic skeletal muscle cells has been examined by transmission electron microscopy; the technique involves preparation using the platinum replication method of freezedried samples, with and without cryofracture. The cytoskeletons in developing muscle cells appear to play a role in preserving cell shape as well as in anchoring myofibrils to cell membrane.

Foetal neurones transplanted within the adult mammalian central nervous system survive and differentiate. Study of such transplants has yielded insights into the function, development and plasticity of brain structures, and suggests promising new therapies for a number of neurological disorders.

Recently a growing number of biologists have begun to consider the causal role that processes of embryonic development may play in evolution. This constitutes a reunion of these phenomena which had been linked in the nineteenth century through Haeckel's biogenetic law. This reunion may result in a new subdiscipline of biology, if there is a set of unique concepts and methods which tie the various research approaches together. Such concepts as bauplan, canalization, and developmental constraint, may serve in (...) such a capacity. The methods employed must combine comparative and experimental analyses, with special attention paid to the range of variation in developmental events within each taxon. These concepts and methods are also applicable to the problem of how development evolved, thus the evolution of development may also be considered part of the reunion. The reunion is discussed in terms of the potential participation of various schools of thought found in the current literature. (shrink)

Graphical AbstractNowadays, in the Internet databases era, certain knowledge is being progressively lost. This knowledge, which we feel is essential and should be acquired through education, is the understanding of how the pioneer researchers faced major questions in their field and made their discoveries.

Normal fetal development is dependent upon an intricate exchange between mother and embryo. Several maternal and embryonic elements can influence this intimate interaction, including genetic, environmental or epigenetic factors, and have a significant impact on embryo development. The interaction of the genetic program of both mother and embryo, within the uterine environment, can shape the development of an individual. Accumulating data from animal models indicate that prenatal events may well initiate long‐term changes in the expression of (...) the embryo genetic program, which persist, or may only become apparent, much later in the individual's life. Also, environmental conditions during prenatal development may prompt the adoption of different developmental pathways, leading to alternative life histories. This review focuses on environmental factors, specifically maternally derived molecules, to illustrate how they can influence in utero embryonic development and, by extension, adult life. (shrink)

Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation (...) together with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development. (shrink)

The earliest source of stem cells in humans are embryos at the blastocyst stage (a hollow ball of about 150–200 cells that is 4–5 days old) of their development. Such cells are identified and collected mainly from surplus embryos discarded after in vitro fertilization (IVF). The procedure requires destruction of the blastocyst. However, embryonic stem cells (ESCs) are immortal in culture and can be grown relatively easily and maintained in permanent culture, frozen and thawed, and transported between laboratories (...) once derived from a pluripotent cell collected from the inner cell mass of the blastocyst. (shrink)