Human embryo: a biological definition

Embryonic and extraembryonic tissues during mammalian development: shifting boundaries in time and space

The first few days of embryonic development in eutherian mammals are dedicated to the specification and elaboration of the extraembryonic tissues. However, where the fetus ends and its adnexa begins is not always as self-evident during the early stages of development, when the definitive body axes are still being laid down, the germ layers being specified and a discrete form or bodyplan is yet to emerge. Function, anatomy, histomorphology and molecular identities have been used through the history of embryology, to make this distinction. In this review, we explore them individually by using specific examples from the early embryo. While highlighting the challenges of drawing discrete boundaries between embryonic and extraembryonic tissues and the limitations of a binary categorization, we discuss how basing such identity on fate is the most universal and conceptually consistent. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.

Developing a Reflexive, Anticipatory, and Deliberative Approach to Unanticipated Discoveries: Ethical Lessons from iBlastoids

In this paper, we explore the recent creation of "iBlastoids," which are 3-D structures that resemble early human embryos prior to implantation which formed via self-organization of reprogrammed adult skin cells. We explore some of the ethical, philosophical, social, and regulatory issues related to this research, with focus particularly on what it means to "anticipate" research outcomes when using novel methods or when serendipitous discoveries are made. We defend the need for reflexive, anticipatory, and deliberative ethical and conceptual work by researchers working in emerging and contentious research domains, in collaboration with interdisciplinary scholars, as well as regulators, funders, and publics.

Embryological development of the human cranio-facial arterial system: a pictorial review

The embryological development of the cerebral vasculature is very complex. Historical and also more recent studies based on human embryos, comparative anatomy and cerebral angiographies allowed us to better understand this vasculature development. The knowledge and understanding of such embryological development are important for physicians interested in neurovascular pathologies. Indeed, all vascular variants and almost all vascular pathologies, such as aneurysms, dolichoectasia, atherosclerosis, and neurovascular conflicts could be explained by an alteration during the embryological life. There are also many variants of these vascular structures present in normal developed adults, which are variably associated with pathological entities. Understanding the process which leads to the development of the normal cerebral arterial system in humans is, therefore, very important to have a better knowledge of the possible clinical and surgical implications of these anomalies. In this paper, we review the embryological development of the cranio-facial arterial vasculature from its beginning at approximately days 21–50 of intrauterine life, with pictures illustrating each developmental phase.

Comparative hematopoiesis and signal transduction in model organisms

Hematopoiesis is a continuous phenomenon involving the formation of hematopoietic stem cells (HSCs) giving rise to diverse functional blood cells. This developmental process of hematopoiesis is evolutionarily conserved, yet comparably different in various model organisms. Vertebrate HSCs give rise to all types of mature cells of both the myeloid and the lymphoid lineages sequentially colonizing in different anatomical tissues. Signal transduction in HSCs facilitates their potency and specifies branching of lineages. Understanding the hematopoietic signaling pathways is crucial to gain insights into their deregulation in several blood-related disorders. The focus of the review is on hematopoiesis corresponding to different model organisms and pivotal role of indispensable hematopoietic pathways. We summarize and discuss the fundamentals of blood formation in both invertebrate and vertebrates, examining the requirement of key signaling nexus in hematopoiesis. Knowledge obtained from such comparative studies associated with developmental dynamics of hematopoiesis is beneficial to explore the therapeutic options for hematopoietic diseases.

First trimester miscarriage: patient care considerations for the dental team

First trimester miscarriage is common, occurring in approximately 6.4-12.0% of pregnancies. Women who experience first trimester miscarriage will often have no other significant health conditions and the healthcare professional they most frequently visit could be their dentist or dental care professional. For this reason, it is important that the dental team is aware of the management of first trimester miscarriage in order to allow for a better understanding of the patient's experience and situation. The choice of language used by healthcare professionals with patients who are grieving is also important to ensure effective and open communication.This article aims to provide the dental team with knowledge of first trimester miscarriage, how the effects of this can be relevant within the dental setting, and how to communicate effectively and appropriately with patients who have experienced this traumatic event.

Ethical Rationales and Guidelines for the Continued Use of Archival Collections of Embryonic and Fetal Specimens

Benefits from the use of cadavers in anatomical education are well described. Historically, human embryos and fetal cadavers were used in anatomy education to understand development and congenital malformations. Recently, three-dimensional printed models produced from archival fetal specimens, and online repositories of images from archival collections of embryos and fetuses, have been used as an educational tool in human development courses. Given that the archival specimens were likely obtained prior to the era of informed consent, this raises questions about their appropriate and ethical use. Because some institutions in the United States retain archival collections of embryonic and fetal specimens that were once used as educational tools, their existence and utility require frequent reexamination against contemporary ethical frameworks to guide appropriate use or utilization. Four ethical rationales for uses of these collections are examined, including destruction, indefinite storage, use in research, and use in health professions education. Guidelines for the use of archival collections of human embryos and fetuses are presented. Indefinite storage and use in health professions education are supported, while use in research is also permitted, however, such use is limited and dependent on circumstance and purpose. The development of current digital repositories and three-dimensionally printed models based on archival collections that were collected without informed consent, or those promoting commercial opportunity, are not supported. New embryonic and fetal donations obtained with informed consent should include reference to potential uses with new technology and virtual, genetic, or imaging applications.

Therapeutic abortion and ectopic pregnancy: alternative sources for fetal stem cell research and therapy in Iran as an Islamic country

Regenerative medicine as a background of stem cell research and therapy has a long history. A wide variety of diseases including Parkinson's disease, heart diseases, multiple sclerosis, spinal cord injury, diabetes mellitus and etc. are candidate to be treated using different types of stem cells. There are several sources of stem cells such as bone marrow, umbilical cord, peripheral blood, germ cells and the embryo/fetus tissues. Fetal stem cells (FSCs) and embryonic stem cells (ESCs) have been described as the most potent stem cell source. Although their pluri- or multipotent properties leads to promising reports for their clinical applications, owning to some ethical and legal obstacles in different communities such as Muslim countries, care should be taken for therapeutic applications of FSCs and ESCs. Derivation of these cell types needs termination of pregnancy and embryo or fetus life that is prohibited according to almost all rules and teaches in Muslim communities. Abortion and termination of pregnancy under a normal condition for the procurement of stem cell materials is forbidden by nearly all the major world religions such as Islam. Legislated laws in the most of Muslim countries permit termination of pregnancy and abortion only when the life of the mother is severely threatened or when continuing pregnancy may lead to the birth of a mentally retarded, genetically or anatomically malformed child. Based on the rules and conditions in Islamic countries, finding an alternative and biologically normal source for embryonic or fetal stem cell isolation will be too difficult. On the one hand, Muslim scientists have the feasibility for finding of genetically and anatomically normal embryonic or fetal stem cell sources for research or therapy, but on the other hand they should adhere to the law and related regional and local rules in all parts of their investigation. The authors suggest that the utilization of ectopic pregnancy (EP) conceptus, extra-embryonic tissues, and therapeutic abortion materials as a valuable source of stem cells for research and medical purposes can overcome limitations associated with finding the appropriate stem cell source. Pregnancy termination because of the mentioned subjects is accepted by almost all Islamic laws because of maternal lifesaving. Also, there are no ethical or legal obstacles in the use of extra-embryonic or EP derived tissues which lead to candidate FSCs as a valuable source for stem cell researches and therapeutic applications.

Perceptions of embryo status and embryo use in an Australian community

Increasingly, important areas of medical therapy and research rely on the donation and use of human embryos. Yet their use is commonly determined by community tolerance and ethico-legal regulation. The aim of this study was to explore the views of an Australian community about what an embryo is, how it should be used and who should make disposition decisions. The findings of a large representative population survey showed that most participants thought of an embryo as human or potentially human but that this did not affect a majority community view that embryos should be used rather than discarded. This study also found divergent views about what the community perceived to be acceptable uses of embryos. The majority perceived the couple as having the authority to make a disposition decision. Women held different views to men across all three questions. The way an embryo was perceived related significantly to how it should be used and who should decide its disposition. These differences and relationships should be considered when developing clinic practices and ethico-legal frameworks to regulate embryo use in science or treatment.

Oocyte-specific deletion of complex and hybrid N-glycans leads to defects in preovulatory follicle and cumulus mass development

Complex and hybrid N-glycans generated by N-acetylglucosaminyltransferase I (GlcNAcT-I), encoded by Mgat1, affect the functions of glycoproteins. We have previously shown that females with oocyte-specific deletion of a floxed Mgat1 gene using a zona pellucida protein 3 (ZP3)Cre transgene produce fewer pups primarily due to a reduction in ovulation rate. Here, we show that the ovulation rate of mutant females is decreased due to aberrant development of preovulatory follicles. After a superovulatory regime of 48 h pregnant mare's serum (PMSG) and 9 h human chorionic gonadotropin (hCG), mutant ovaries weighed less and contained approximately 60% fewer preovulatory follicles and more atretic and abnormal follicles than controls. Unlike controls, a proportion of mutant follicles underwent premature luteinization. In addition, mutant preovulatory oocytes exhibited gross abnormalities with approximately 36% being blebbed or zona-free. While 97% of wild-type oocytes had a perivitelline space at the preovulatory stage, approximately 54% of mutant oocytes did not. The cumulus mass surrounding mutant oocytes was also smaller with a decreased number of proliferating cells compared with controls, although hyaluronan around mutant oocytes was similar to controls. In addition, cumulus cells surrounding mutant eggs were resistant to removal by either hyaluronidase or incubation with capacitated sperm. Therefore, the absence of complex and hybrid N-glycans on oocyte glycoproteins leads to abnormal folliculogenesis resulting in a decreased ovulation rate.

The beginning of human life : status of embryo. Perspectives in Halakha (Jewish Religious Law)

INTRODUCTION

The Jewish religion is characterized by a strict association between faith and practical precept. Jewish law has two sections, the written and the oral tradition. The foundation of the written law and the origin of authority is the Torah, the first five books of the Scripture. It is an expression of God's revelation, teaching and guiding humanity. The oral laws interpret, expand, and elucidate the written Torah and behavior patterns regulate new rules and customs. The main parts of the oral law are as follows: the Mishnah, the Talmud, Post-Talmudic Codes and. Responsa Literature.

DISCUSSION

Life is a process that has a beginning and an end. The consensus about the time when human life really begins is still not reached among scientists, philosophers, ethicists, sociologists and theologizes. The scientific data suggested that a single developmental moment marking the beginning of human life does not exist. Current biological perspectives on when human life begins range through fertilization, gastrulation, to birth and even after. The development of a newborn is a smoothly continuous process.

RESULTS

Procreation is acknowledged in the Bible to be the gift of God. The (Halachic) Jewish interpretation of when human life begins is extracted predominantly from procreation is acknowledged in the Bible to be the gift of God. The Jewish interpretation of when human life begins is extracted predominantly from The Halachic sources. The Bible does not make any other direct references regarding the beginning of human life.

CONCLUSION

While the Talmud gives the full status of humanness to a child at birth, the rabbinical writings have partially extended the acquisition of humanness to the 13th postnatal day of life for full-term infants. The Babylonian Talmud Yevamot 69b states that: "the embryo is considered to be mere water until the fortieth day." Afterwards, it is considered subhuman until it is born. The issues of abortion, embryo research, multifetal reduction and cloning will be discussed according to Jewish Law perspectives. Life is a process that has a beginning and an end. The consensus about the time when human life really begins is still not reached among scientists, philosophers, ethicists, sociologists and theologizes. The scientific data suggested that a single developmental moment marking the beginning of human life does not exist. Current biological perspectives on when human life begins range through fertilization, gastrulation, to birth and even after. The development of a newborn is a smoothly continuous process.

The debate surrounding human embryonic stem cell research in the USA

Despite its potential for reducing human suffering, the advancement of human embryonic stem cell research has not been given top priority by the US government, and the scientific community has been engaged in a debate on this issue in the USA and beyond. The central question in this debate is whether the promise of stem cells justifies the destruction of human embryos - mainly embryos that are surplus to the needs of patients undergoing infertility treatment. It is argued here that this debate belongs in the same category as the debates on global warming and evolution, because it has much in common with both. It is conducted with a heavy load of scientifically uninformed views and beliefs and framed largely by an implacable opposition with the aim of creating public confusion and doubt. It is primarily politically motivated and, as is true about the debate on evolution, it is rooted in religion. A human embryo is not a human being or person even if it is deserving of - and receives - respect and extraordinary care in the context of assisted human reproduction. Rather than engaging in a futile debate that clouds the way forward in a vital branch of biology, scientists ought to continue to emphasize the importance of human embryo research.