Embryonic stem cells alone are able to support fetal development in the mouse

The developmental potential of embryonic stem (ES) cells versus 3.5 day inner cell mass (ICM) was compared after aggregation with normal diploid embryos and with developmentally compromised tetraploid embryos. ES cells were capable of colonizing somatic tissues in diploid aggregation chimeras but less efficiently than ICMs of the same genotype. When ICM in equilibrium with tetraploid and ES in equilibrium with tetraploid chimeras were made, the newborns were almost all completely ICM- or ES-derived, as judged by GPI isozyme analysis, but tetraploid cells were found in the yolk sac endoderm and trophectoderm lineage. Investigation of ES contribution in 13.5 day ES in equilibrium with tetraploid chimeras by DNA in situ hybridization confirmed the complete tetraploid origin of the placenta (except the fetal blood and blood vessels) and the yolk sac endoderm. However, the yolk sac mesoderm, amnion and fetus contained only ES-derived cells. ES-derived newborns failed to survive after birth, although they had normal birthweight and anatomically they appeared normal. This phenomenon remains unexplained at the moment. The present results prove that ES cells are able to support complete fetal development, resulting in ES-derived newborns, and suggest a useful route for studying the development of genetically manipulated ES cells in all fetal lineages.     

Embryonic and fetal hemopoiesis: an overview

Our current knowledge of embryonic and fetal hemopoiesis is critically reviewed in this article. In both murine and human systems, embryonic and fetal development is associated with multiple switching in the sites of hemopoiesis. The phenomenon is first extraembryonic, occurring in blood islands of the yolk sac. Hemopoietic stem cells (HSC) appear to derive from hemangioblasts that are of mesodermal origin. Yolk sac milieu is permissive only for erythropoiesis which proceeds synchronously and may be erythropoietin-insensitive. Yolk sac milieu is not permissive for the development of other cell lines. The final product is nucleated red cells. Yolk sac hemopoiesis is an example par excellence of primitive (as compared to definitive) form of hemopoiesis. HSC then seem to migrate via the bloodstream to the liver and spleen to seed these tissues, which then carry the burden of hemopoiesis until birth and for some time thereafter. Here also erythropoiesis predominates, but some granulopoiesis also occurs. Thus, the milieu is not totally impermissive. Hemopoiesis is in definitive form, lacking synchronicity of cell growth with the end product being anucleated cells and synthesized hemoglobin not limited to embryonic type. The site of hemopoiesis is finally transferred to the bone marrow, which is predominantly granulopoietic. Certain cellular and embryological features of these types of hemopoiesis in the context of more recent molecular understanding of stem cell homing are discussed.     

Embryonic and fetal programming of physiological disorders in adulthood

In the past decade, data from numerous epidemiological studies have indicated strong inverse associations between birth weight and risk of coronary heart disease, hypertension, type 2-diabetes, and other diseases in adulthood. The "Barker hypothesis" thus postulates that a number of organ structures and functions undergo programming during embryonic and fetal life. This developmental programming determines the set points of physiological and metabolic responses in adult life. Alterations of nutrient availability during gestation may lead to developmental adaptations, via hormonal maneuvers by the embryo and fetus that readjust these set points. These adaptive measures have short-term benefits to the embryo and fetus, so that the newborn will be better prepared for the adverse environment (e.g., undernutrition). However, adequate nutritional support during postnatal life that enables catch-up growth may create metabolic conflicts that predispose the adult to aberrant physiological functions and, ultimately, increased risk of disease. It is plausible that other adverse in utero conditions, including exposure to developmental toxicants, may similarly alter adult disease susceptibility. This article provides an overview of the Barker hypothesis, its supporting evidence, the current advances in understanding the biological mechanisms underlying this phenomenon, and its implications for developmental toxicology.     

Embryonic development in Erythrocebus patas

The developmental stages of 12 Erythrocebus patas embryos, ranging in gestational age from 30 to 50 days, is described. The pattern of embryogenesis in E. patas closely parallels the anatomic characteristics of human and other nonhuman primate embryos between stages 12 and 23. However, there is a delay in development in E. patas similar to that observed in human embryos which differs from the macaques and baboons. This temporal difference in the embryonic period is an important factor in the design and analysis of early pregnancy studies in this species.     

Embryonic and fetal hemoglobin synthesis in K562 cell line

K562 cell line was grown in liquid suspension and in plasma clot cultures. Morphological studies revealed the presence of a minority of cells, which were identified as erythroblasts. However, the majority of the cells remained unidentified. Biochemical studies confirmed the synthesis of hemoglobin by K562 cells. The pattern of hemoglobin (Hb) production was of the embryonic type, with the presence of small amount of fetal Hb. The addition of several inducers, like Epo and butyrate, was unable to modify the pattern of Hb production of K562. In contrast, the addition of hemin increased the synthesis of Hb and stimulated the synthesis of fetal Hb and probably adult Hb.     

Embryonic skin development and repair

Fetal cutaneous wounds have the unique ability to completely regenerate wounded skin and heal without scarring. However, adult cutaneous wounds heal via a fibroproliferative response which results in the formation of a scar. Understanding the mechanism(s) of scarless wound healing leads to enormous clinical potential in facilitating an environment conducive to scarless healing in adult cutaneous wounds. This article reviews the embryonic development of the skin and outlines the structural and functional differences in adult and fetal wound healing phenotypes. A review of current developments made towards applying this clinical knowledge to promote scarless healing in adult wounds is addressed.     

Embryonic stem cell development in a chemically defined medium

Vertebrate germ layer development is an intricately interwoven process with the organism operating as an integrated whole. To examine these processes we have used embryonic stem (ES) cell in vitro differentiation in a serum-free, chemically defined medium (CDM). In CDM, ES cells differentiate as embryoid bodies to neuroectoderm with upregulation of pax-6, without commensurate expression of Brachyury. In the presence of Activin A, pax-6 and Brachyury mRNAs are readily detectable, suggestive of both neuroectoderm and mesoderm formation, while in the presence of BMP-4 a process resembling primitive streak formation at the molecular level occurs. Neuroectoderm development in CDM alone is consistent with the view that this process can occur by default, as reported in Xenopus, due to the absence or sequestration of mesoderm-inducing factors. Additionally, these data show that BMP-4 alone is capable of instigating a process resembling primitive streak formation in ES cells and possibly in vivo.     

Pregnancy diagnosis and assessment of fetal numbers in the ewe in a commercial setting

Jugular plasma progesterone concentrations were used to accurately predict open ewes (96 +/- 3%) in early pregnancy, but they less accurately predicted subsequent lambing especially during the late breeding season and most of the seasonal anestrus. Progesterone values clearly indicated that 500 I.U. of P.M.S.G. elevated ovulation rate in synchronized ewes, but did not clearly indicate fetal numbers. During late pregnancy (88-108 days), abdominal palpation, doplar ultrasound and serum progesterone analysis were equally efficacious in predicting lambing (86 +/- 9.8%, 90 +/- 9.0% and 87 +/- 4.1%, respectively), but a high percentage of ewes lambed that were diagnosed as nonpregnant (30 +/- 15.0%, 48 +/- 17.3% and 25 +/- 8.4%, respectively). Accuracy of the serum progesterone test improved the later the test was performed, although considerable individual overlap existed. Progesterone values for ewes bearing 1, 2, or greater than 2 fetuses at 94 to 95 days of gestation differed (5.5 +/- 0.3, 8.0 +/- 0.4 and 12.4 +/- 2.1, respectively (P < 0.05), whereas at 103 to 108 days values for ewes carrying two or more fetuses did not differ.     

Embryonic and larval development of a cold adapted Antarctic ascidian

Ova of the Antarctic ascidian Cnemidocarpa verrucosa were mature at 240–245 μm. At 0 to −1.5°C, embryos hatched as swimming tadpoles at 8 days from fertilization, which is close to the ages at which some Antarctic echinoderm and nemertean embryos hatch as blastulae. Comparisons of Antarctic and temperate ascidian larvae suggest that the ascidian’s development rate is affected by low environmental temperatures to about the same extent as embryos and larvae of an echinoid, nemertean, and calanoid copepods. The ascidian’s tadpoles were bright orange and large, >2 mm in length including tunic and >1.5 mm in length without tunic. The large and brightly colored tadpoles were conspicuous when swimming, which supports the hypothesis that larvae of C. verrucosa are chemically defended against predators. Metamorphosed juveniles were found in cultures within 16 days from fertilization, when some unsettled tadpoles still moved but were less active. The potential pelagic period may therefore be 16 or more days with 8 days as an unhatched embryo and up to 8 or more days as a tadpole. The resting metabolic rate of tadpole larvae was 15 pmol O₂ h⁻¹ individual⁻¹ which is equivalent to larval respiration rates in Antarctic echinoderms. A low resting metabolic rate suggests a potential mechanism for the extended larval lifespan in C. verrucosa.     

Embryonic and fetal rat myoblasts express different phenotypes following differentiation in vitro

Myosin heavy chain (MHC) is encoded by a multigene family containing members which are expressed in developmental and fiber type-specific patterns. In developing rats, primary (1°) and secondary (2°) myotjbes can be disfinguished by differences in MHC expression: 1° myotubes coexpress embryonic and slow MHC, while 2° myotubes initially express only embryonic MHC. We have used monoclonal antibodies which recognize the embryonic, slow, neonatal, and adult fast IIB/IIX MHCs to examine MHC accumulation in myoblasts obtained from hindlimbs of embryonic day (ED) 14 and ED 20 Sprague-Dawley rats during differentiation in vitro. Embryonic myoblasts (ED 14), which develop into 1° myotubes in vivo, differentiate as myocytes or small myotubes (i.e., 1–4 nuclei) which express both embryonic and slow MHC. They do not accumulate detectable levels of neonatal or adult fast IIB/IIX MHC. Fetal myoblasts, which develop into secondary myotubes in vivo, fuse to form large myotubes (i.e., 10–50 nuclei) and express predominantly embryonic MHC at 3 days in culture. These myotubes accumulate neonatal and adult fast IIB/IIX isoforms of MHC and eventually contract spontaneously. In contrast to embryonic myotubes, they do not accumulate slow MHC. Our results demonstrate that embryonic and fetal rat myoblasts express different phenotypes in vitro and suggest that they represent distinct myoblast lineages similar to those previously described in chickens and mice. These two lineages may be responsible for the generation of distinct populations of 1° and 2° myotubes in vivo. © 1993Wiley-Liss, Inc.     

双斑蟋的胚胎发育

为了从组织胚胎学角度探究昆虫胚胎发育过程,以双斑蟋Gryllus bimaculatus de Geer的卵为实验材料,通过观察、记录蟋蟀胚胎每一天的形态变化并使用显微摄影方法记录胚胎发育过程,对蟋蟀卵胚胎发育全过程进行系统的观察和研究。根据胚胎形态的发育特点,可将整个胚胎发育过程分为7个阶段:卵裂期、囊胚期、原肠胚、无节幼体期Ⅰ、无节幼体期Ⅱ、无节幼体期Ⅲ、无节幼体期Ⅳ。经历14天,蟋蟀的头部、触角、3对足、尾部、腹部及背部都发育完全,整个胚胎发育随之结束。     

Canine embryonic and fetal development: a review

The progression from a fertilized oocyte to a newborn puppy is a remarkable phenomenon that occurs in a period of approximately two months. Embryonic development encompasses the period of time at which three germ layers differentiate: ectoderm, mesoderm, and endoderm. Organ systems are formed from these germ layers, with most of the reproductive tract being derived from mesoderm. Organogenesis is complete prior to the fetal stage in canine embryos, but sexual differentiation occurs during the fetal stage. Sexual differentiation is a well-coordinated progression of events that is directed initially by the genotype of the developing embryo and fetus. Developing fetuses are inherently female and will develop as such in the absence of a Y chromosome. Male fetuses develop as the Y chromosome causes regression of the female duct system and development of the male duct system. Testicular descent in the canine begins in the fetal stage, but is not completed until after birth.     

Embryonic development clarifies polyphyly in ostracod crustaceans

The present study describes the embryonic developmental process of the bioluminescent ostracod crustacean Vargula hilgendorfii . Optical microscopy, scanning electron microscopy, DAPI staining and video recording were used for observations. This study is the first detailed report of the embryonic development of a myodocopid ostracod. Contrary to previous studies, cleavage occurred in the yolk sphere and no evident cleavage furrow was found. No nauplius stage was found, and five pairs of appendages developed simultaneously. A bivalved carapace developed from two independent buds of the carapace valves. The buds of the left and right valves are enlarged, and become combined. The combined 'one-piece' carapace was divided by the formation of a hinge, and the usual bivalved carapace was formed. On the 16th day, embryos hatched as juveniles with six pairs of appendages, a pair of immature appendages, a pair of compound eyes, a median eye and a bivalved carapace. An important suggestion for the classification of Ostracoda is derived from the observed development of appendages and carapace, because the subclass Ostracoda is defined mainly by the similarities of appendages and the bivalved carapace. The present observations clearly show that the developmental process of Myodocopa differs from that of Podocopa, and supports polyphyly of the Ostracoda.     

Embryonic quail eye development in microgravity.

The US-Russian joint quail embryo project was designed to study the effects of microgravity on development of Japanese quail embryos incubated aboard Mir. For this part of the project, eyes from embryonic days 14 and 16 (E14 and E16) flight embryos were compared with eyes from several groups of ground-based control embryos. Measurements were recorded for eye weights; eye, corneal, and scleral ring diameters; and numbers of bones in scleral ossicle rings. Transparency of E16 corneas was documented, and immunohistochemical staining was performed to observe corneal innervation. In addition, corneal ultrastructure was observed at the electron microscopic level. Except for corneal diameter of E16 flight embryos, compared with that of one of the sets of controls, results reported here indicate that eye development occurred normally in microgravity. Fixation by cracking the shell and placing the egg in paraformaldehyde solution did not adequately preserve corneal nerves or cellular ultrastructure.     

Sulfate in fetal development

Sulfate (SO(4)(2-)) is an important nutrient for human growth and development, and is obtained from the diet and the intra-cellular metabolism of sulfur-containing amino acids, including methionine and cysteine. During pregnancy, fetal tissues have a limited capacity to produce sulfate, and rely on sulfate obtained from the maternal circulation. Sulfate enters and exits placental and fetal cells via transporters on the plasma membrane, which maintain a sufficient intracellular supply of sulfate and its universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) for sulfate conjugation (sulfonation) reactions to function effectively. Sulfotransferases mediate sulfonation of numerous endogenous compounds, including proteins and steroids, which biotransforms their biological activities. In addition, sulfonation of proteoglycans is important for maintaining normal structure and development of tissues, as shown for reduced sulfonation of cartilage proteoglycans that leads to developmental dwarfism disorders and four different osteochondrodysplasias (diastrophic dysplasia, atelosteogenesis type II, achondrogenesis type IB and multiple epiphyseal dysplasia). The removal of sulfate via sulfatases is an important step in proteoglycan degradation, and defects in several sulfatases are linked to perturbed fetal bone development, including mesomelia-synostoses syndrome and chondrodysplasia punctata 1. In recent years, interest in sulfate and its role in developmental biology has expanded following the characterisation of sulfate transporters, sulfotransferases and sulfatases and their involvement in fetal growth. This review will focus on the physiological roles of sulfate in fetal development, with links to human and animal pathophysiologies.     

Embryonic development in ballan wrasse Labrus bergylta

Eight primary embryonic developmental stages were assigned to eggs of ballan wrasse Labrus bergylta using key morphological features following standardized nomenclature: Ia, Ib, II, III, IV, V, VI and VI+, reared from single family clutches under comparable environmental conditions in Ireland and Norway. Development in L. bergylta is typical of demersal marine finfish species with a short egg stage. Hatching occurred c. 123 h post-fertilization (hpf) equivalent to 62·5 degree days at 12·2 ± 1·10° C (mean ±s.d.), after which the larvae swam intermittently near the surface of the water column.     

Iron and copper in fetal development

Copper and iron are both essential micronutrients. Because they can both accept and donate electrons, they are central to many energy dependent chemical reactions. For example, copper is a critical part of ferroxidase enzymes ceruloplasmin, hephaestin and zyklopen, as well as enzymes such as dopamine-β-monoxygenase, while iron is part of the catalytic site of many cytochromes and enzymes involved in fatty acid desaturation. Unsurprisingly, therefore, copper and iron deficiency, especially during pregnancy, when cell proliferation and differentiation are very active, sub-optimal nutrient status can lead to serious consequences. These problems can persist into adulthood, with an increased risk of mental problems such as schizophrenia and, in animal models at least, hypertension and obesity. In this review, we consider what these problems are and how they may arise. We examine the role of copper and iron deficiencies separately during fetal development, in terms of birth outcome and then how problems with status in utero can have long term sequelae for the offspring. We examine several possible mechanisms of action, both direct and indirect. Direct causes include, for example, reduced enzyme activity, while indirect ones may result from changes in cytokine activity, reductions in cell number or increased apoptosis, to name but a few. We examine a very important area of nutrition-interactions between the micronutrients and conclude that, while we have made significant advances in understanding the relationship between micronutrient status and pregnancy outcome, there is still much to be learned.