METAPHILOSOPHY, Issue 2-3 2007
KATRIEN DEVOLDER
Abstract: We argue in this essay that (1) the embryo is an irredeemably ambiguous entity and its ambiguity casts serious doubt on the arguments claiming its full protection or, at least, protection against its use as a means for stem cell research, (2) those who claim the embryo should be protected as "one of us" are committed to a position even they do not uphold in their practices, (3) views that defend the protection of the embryo in virtue of its potentiality to become a person fail, and (4) the embryo does not have any rights or interests to be protected. Given that many are willing to treat the embryo as a means in other practices, and that human embryonic stem cell (hESC) research holds great potential to benefit many people, one cannot but conclude that hESC research is permissible and, because of its immense promise for alleviating human suffering, even obligatory. [source]

EFFECTS OF UV RADIATION ON GROWTH AND PHLOROTANNINS IN FUCUS GARDNERI (PHAEOPHYCEAE) JUVENILES AND EMBRYOS,

JOURNAL OF PHYCOLOGY, Issue 3 2004
Brianne E. Henry
Diminishing levels of atmospheric ozone are increasing UV stress on intertidal algae. Early developmental stages tend to be more susceptible to environmental stresses; however, little research has examined how these stages are protected from UV radiation (UVR). Many brown algae contain high levels of phlorotannins, which are thought to function in screening UVR. In this study, we tested the effects of ambient levels of UV-B and UV-A on growth and phlorotannin production in 1- to 2-cm juvenile and microscopic postsettlement embryos of the intertidal alga Fucus gardneri Silva. Algae were grown in four light treatments: 1) ambient light; 2) under cellulose acetate, which lowered light quantity but did not affect light quality; 3) under MylarTM, which filtered UV-B; and 4) under PlexiglasTM, which blocked UV-A and UV-B. Over a 3-week period, UV-B inhibited and UV-A enhanced the growth of F. gardneri embryos, whereas the growth of juveniles was not affected. Phlorotannin concentrations of both embryos and juveniles did not differ in any of the light treatments. Our results suggest that embryos of F. gardneri are susceptible to UV light but develop a tolerance to it as they mature. This tolerance may result from increases in phlorotannin concentrations that occur during maturation; however, phlorotannin production in embryonic or juvenile stages is either not induced by UV light or takes more than 3 weeks to occur. [source]

IN VITRO SOMATIC EMBRYOGENESIS AND REGENERATION OF SOMATIC EMBRYOS FROM PIGMENTED CALLUS OF KAPPAPHYCUS ALVAREZII (DOTY) DOTY (RHODOPHYTA, GIGARTINALES),

JOURNAL OF PHYCOLOGY, Issue 3 2003
C. R. K. Reddy
In vitro somatic embryogenesis and regeneration of somatic embryos to whole plants through micropropagules was successfully demonstrated from pigmented uniseriate filamentous callus of Kappaphycus alvarezii (Doty) Doty in axenic cultures. More than 80% of the explants cultured on 1.5% (w/v) agar-solidified Provasoli enriched seawater (PES) medium showed callus development. The callus induction rate was consistently higher for laboratory-adapted plants. The excised callus grew well in subcultures and maintained its growth for prolonged periods if transferred to fresh medium in regular intervals. Some subcultured calli (<10%) did undergo transformation and produced densely pigmented spherical or oval-shaped micropropagules (1,5 mm in diameter) that subsequently developed into young plantlets in liquid PES medium. The micropropagule production was further improved through somatic embryogenesis by a novel method of culturing thin slices of pigmented callus with naphthaleneacetic acid (NAA) or a mixture of NAA and 6-benzylaminopurine. Transfer of embryogenic callus along with tiny somatic embryos to liquid medium and swirling on orbital shaker facilitated rapid growth and morphogenesis of somatic embryos into micropropagules that grew into whole plants in subsequent cultivation in the sea. The daily growth rate of one tissue cultured plant was monitored for seven generations in field and found to be as high as 1.5,1.8 times over farmed plants. The prolific somatic embryogenesis together with high germination potential of somatic embryos observed in this study offers a promising tool for rapid and mass clonal production of seed stock of Kappaphycus for commercial farming. [source]

KILLING EMBRYOS FOR STEM CELL RESEARCH

METAPHILOSOPHY, Issue 2-3 2007
JEFF MCMAHAN
Abstract: The main objection to human embryonic stem cell research is that it involves killing human embryos, which are essentially beings of the same sort that you and I are. This objection presupposes that we once existed as early embryos and that we had the same moral status then that we have now. This essay challenges both those presuppositions, but focuses primarily on the first. I argue first that these presuppositions are incompatible with widely accepted beliefs about both assisted conception and monozygotic twinning. I then argue that we never existed as embryos. If this last claim is right, killing an embryo does not kill someone like you or me but merely prevents one of us from existing. [source]

DONATING FRESH VERSUS FROZEN EMBRYOS TO STEM CELL RESEARCH: IN WHOSE INTERESTS?

BIOETHICS, Issue 9 2007
CAROLYN MCLEOD
ABSTRACT Some stem cell researchers believe that it is easier to derive human embryonic stem cells from fresh rather than frozen embryos and they have had in vitro fertilization (IVF) clinicians invite their infertility patients to donate their fresh embryos for research use. These embryos include those that are deemed ,suitable for transfer' (i.e. to the woman's uterus) and those deemed unsuitable in this regard. This paper focuses on fresh embryos deemed suitable for transfer , hereafter ,fresh embryos', which IVF patients have good reason not to donate. We explain why donating them to research is not in the self-interests specifically of female IVF patients. Next, we consider the other-regarding interests of these patients and conclude that while fresh embryo donation may serve those interests, it does so at unnecessary cost to patients' self-interests. Lastly, we review some of the potential barriers to the autonomous donation of fresh embryos to research and highlight the risk that female IVF patients invited to donate these embryos will misunderstand key aspects of the donation decision, be coerced to donate, or be exploited in the consent process. On the basis of our analysis, we conclude that patients should not be asked to donate their fresh embryos to stem cell research. [source]

Potential roles for BMP and Pax genes in the development of iris smooth muscle

DEVELOPMENTAL DYNAMICS, Issue 2 2005
Abbie M. Jensen
Abstract The embryonic optic cup generates four types of tissue: neural retina, pigmented epithelium, ciliary epithelium, and iris smooth muscle. Remarkably little attention has focused on the development of the iris smooth muscle since Lewis ([1903] J. Am. Anat. 2:405,416) described its origins from the anterior rim of the optic cup neuroepithelium. As an initial step toward understanding iris smooth muscle development, I first determined the spatial and temporal pattern of the development of the iris smooth muscle in the chick by using the HNK1 antibody, which labels developing iris smooth muscle. HNK1 labeling shows that iris smooth muscle development is correlated in time and space with the development of the ciliary epithelial folds. Second, because neural crest is the only other neural tissue that has been shown to generate smooth muscle (Le Lievre and Le Douarin [1975] J. Embryo. Exp. Morphol. 34:125,154), I sought to determine whether iris smooth muscle development shares similarities with neural crest development. Two members of the BMP superfamily, BMP4 and BMP7, which may regulate neural crest development, are highly expressed by cells at the site of iris smooth muscle generation. Third, because humans and mice that are heterozygous for Pax6 mutations have no irides (Hill et al. [1991] Nature 354:522,525; Hanson et al. [1994] Nat. Genet. 6:168,173), I determined the expression of Pax6. I also examined the expression of Pax3 in the developing anterior optic cup. The developing iris smooth muscle coexpresses Pax6 and Pax3. I suggest that some of the eye defects caused by mutations in Pax6, BMP4, and BMP7 may be due to abnormal iris smooth muscle. Developmental Dynamics 232:385,392, 2005. © 2004 Wiley-Liss, Inc. [source]

Comparative sensitivity of embryo,larval toxicity assays with African catfish (Clarias gariepinus) and zebra fish (Danio rerio)

ENVIRONMENTAL TOXICOLOGY, Issue 6 2001
Lien T. H. Nguyen
Abstract Embryo,larval toxicity tests with the African catfish (Clarias gariepinus) were conducted with five chemicals (Cr, Cd, Zn, NaPCP and malathion) and three environmental samples. The sensitivity of the 5-day assay was compared to that of the 12-day embryo,larval toxicity tests with the zebra fish (Danio rerio). The ratios of the C. gariepinus and D. rerio LC50 values ranged from 0.4 for Cr to 8.9 for Zn. The ratios of subchronic values ranged from 0.25 for NaPCP to 3.1 for Cd indicating a more comparable sensitivity of the two species. For the three sediment pore waters, the ratios were 0.6, 1.1, and 2.4 and the subchronic values were identical for the two species. The results suggest that, considering the short-test duration and its sensitivity, the 5-day embryo,larval tests with C. gariepinus may be a potential alternative for short-term embryo,larval toxicity testing with fish. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 566,571, 2001 [source]

Embryo of an annual fish (Austrolebias charrua) in the last dormancy stage, diapause III

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 1 2009
Article first published online: 22 JAN 200
Embryo of an annual fish (Austrolebias charrua) in the last dormancy stage, diapause III. The embryo, surrounded by a transparent vitelline envelope, is in the pre-hatching stage. A prominent eye and part of the pigmented body and tail are apparent. Why annual fishes? Annual fishes (Order Cyprinodontiformes) are a special kind of teleost, found in Africa and South America, with developmental strategies closely related to their life cycle. These fishes inhabit temporary pools that undergo drying during summer, when all adults die. The embryos remain buried in the bottom mud and are resistant to desiccation. In the subsequent rainy season they hatch a few hours after the pool is flooded and a new reproductive cycle begins. This developmental pattern is characterized by the presence of a unique stage between cleavage and embryogenesis, dispersion-aggregation of blastomeres and because the embryos show reversible developmental arrests (diapauses) at different stages. Annual fish embryos are transparent, large, hardy and easy to maintain in the laboratory. Adults show continuous production of eggs and juveniles reach sexual maturity a few weeks after hatching (an unusual condition in fishes). Their particular developmental features confer unique opportunities for research on cell behavior during early development, the effect of environmental factors on development, the regulation of diapauses and the mechanisms involved in sex determination, among others topics. Image provided by Nibia Berois, Universidad de la República, Montevideo, Uruguay. [source]

Embryo medley from the Woods Hole Embryology Course of 2008

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 10 2008
Article first published online: 17 OCT 200
Top edge: Body wall of the annelid Pristina leidya (Jesse Meik and Ian Swinburne). Right edge: Embryo of the grasshopper, Schistocerca americana (R'ada Massarwa). Bottom edge: Drosophila melanogaster embryo (Courtney Karner). Bottom left corner: Mouse embryo (Marie-Therese Noedl). Left upper row: Adult annelid Pristina leidyi (Michelle Collins and Stephanie Lepage). Middle upper row: Embryo of the squid Loligo pealii (Andrew Chervenak). Right upper row: larva of the colonial ascidian, Botrylloides (Jessica Gray). Left lower row: Chick embryo (Benjamin Schlager). Middle lower row: Xenopus laevis (Brooke Armfield and Zacharias Kontarakis). Right lower row: Third instar CNS and disks of Drosophila melanogaster (Jenna Judge). For more information on the Woods Hole Embrylology Course, visit http://www.mbl.edu/education/courses/summer/course_embryo.html [source]

Strange Anatomy: Gertrude Stein and the Avant-Garde Embryo

HYPATIA, Issue 1 2006
Lynn M. Morgan
Today's personable, sanitized images of human embryos and fetuses require an audience that is literally and metaphorically distanced from dead specimens. Yet scientists must handle dead specimens to produce embryological knowledge, which only then can be transformed into beautiful photographs and talking fetuses. I begin with an account of Gertrude Stein's experience making a model of a fetal brain. Her tactile encounter is contrasted to the avant-garde artistic tradition that later came to dominate embryo imagery. This essay shows the embryo visualizations portrayed in a contemporary coffee-table book about gestational development to be a remarkable political achievement predicated, in part, on keeping hidden the unsavory details of anatomical technique that transform dead specimens into icons of life. [source]

The Anatomy of the Human Embryo: A Scanning Electron-Microscope Atlas

JOURNAL OF ANATOMY, Issue 5 2009
Gillian Morriss-Kay
No abstract is available for this article. [source]

Reactive Oxygen Species Scavenging Enzymes and Down-Adjustment of Metabolism Level in Mitochondria Associated with Desiccation-Tolerance Acquisition of Maize Embryo

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2009
Jing-Hua Wu
Abstract It is a well-known fact that a mature seed can survive losing most of its water, yet how seeds acquire desiccation-tolerance is not well understood. Through sampling maize embryos of different developmental stages and comparatively studying the integrity, oxygen consumption rate and activities of antioxidant enzymes in the mitochondria, the main origin site of reactive oxygen species (ROS) production in seed cells, we found that before an embryo achieves desiccation-tolerance, its mitochondria shows a more active metabolism, and might produce more ROS and therefore need a more effective ROS scavenging system. However, embryo dehydration in this developmental stage declined the activities of most main antioxidant enzymes and accumulated thiobarbituric acid-reactive products in mitochondria, and then destroyed the structure and functional integrity of mitochondria. In physiologically-matured embryos (dehydration-tolerant), mitochondria showed lower metabolism levels, and no decline in ROS scavenging enzyme activities and less accumulation of thiobarbituric acid-reactive products after embryo dehydration. These data indicate that seed desiccation-tolerance acquisition might be associated with down-adjustment of the metabolism level in the late development stage, resulting in less ROS production, and ROS scavenging enzymes becoming desiccation-tolerant and then ensuring the structure and functional integrity of mitochondria. [source]

Expression of Genes in the Canine Pre-implantation Uterus and Embryo: Implications for an Active Role of the Embryo Before and During Invasion

REPRODUCTION IN DOMESTIC ANIMALS, Issue 6 2008
S Schäfer-Somi
Contents The aim of the present study was to assess genes expressed in maternal uterine tissue and pre-implantation embryos which are presumably involved in maternal recognition and establishment of canine pregnancy. For this purpose, 10 pregnant bitches were ovariohysterectomized between days 10 and 12 after mating. Four non-pregnant bitches served as controls. Early pregnancy was verified by flushing the uterine horns with PBS solution. The collected embryos (n = 60) were stored deep-frozen (,80°C). Uterine tissue was excised, snaps frozen in liquid nitrogen and homogenized using TRI Reagent. All embryos from one litter were thawed together and also homogenized in TRI Reagent. RT-PCR was performed to prove mRNA expression of progesterone receptor, key enzymes of the prostaglandin synthesis pathway, selected growth factors, cytokines, immune cell receptors, major histocompatibility complex (MHC) and matrix-metalloproteinases (MMP). Only pregnant uteri revealed the presence of mRNA for interferon (IFN)-,, IL-4 and CD-8, which resembles the milieu in humans and other mammalians. Similarly, in day 10 embryos, mRNA for transforming growth factor-,, insulin-like growth factor-1,-2, hepatocyte growth factor, leukaemia inhibitor factor, tumour necrosis factor-,, interleukin-1,,-6,-8, cyclooxygenase-2, CD4+ cells, and MMP-2 and -9 were detected, but not MHC-I or -II. We therefore suppose that the canine embryo, like its human counterpart, actively initiates measures to prevent attacks from the maternal immune system to prepare its own adhesion, nidation, growth and further development. [source]

Stage-specific Expression of Leukaemia Inhibitory Factor and its Receptor in Rabbit Pre-implantation Embryo and Uterine Epithelium During Early Pregnancy

REPRODUCTION IN DOMESTIC ANIMALS, Issue 1 2004
T Lei
Contents Leukaemia inhibitory factor (LIF) has been shown to play an important role in the development and implantation of blastocysts in mice. In the current study, the reverse transcription,polymerase chain reaction (RT-PCR) was employed to examine the expression patterns of LIF and its receptor (LIFR) genes in rabbit embryos during pre-implantation development, and the uterine expression of LIF and LIFR was also evaluated by Western blotting. Transcripts for LIFR were detected within morula and blastocyst-stage embryos, while the LIF mRNA was only found in blastocysts (from early to fully expanded blastocoel cavities), indicating that embryo-derived LIF can act in an autocrine manner on the process of blastocyst formation. The expression levels of LIF and LIFR in uterine epithelium were gradually increased during pre-implantation period and reached their highest levels on days 6.5 of pregnancy, just before the time of blastocyst implantation, suggest that paracrine LIF circuit should exist between the endometrium and the early embryos, which may be involved in the embryo-maternal dialogue and important for the blastocyst implantation. The data present here show the stage-specific and dynamic expression patterns of LIF and LIFR, both in embryos and endometrium, during early pregnancy in rabbits, which indicated that LIF might play an important role in the pre-implantation development and subsequent implantation of rabbit embryos. [source]

Development of the Tarsometatarsal Skeleton by the Lateral Fusion of Three Cylindrical Periosteal Bones in the Chick Embryo (Gallus gallus)

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 9 2010
Yuichi Namba
Abstract An avian tarsometatarsal (TMT) skeleton spanning from the base of toes to the intertarsal joint is a compound bone developed by elongation and lateral fusion of three cylindrical periosteal bones. Ontogenetic development of the TMT skeleton is likely to recapitulate the changes occurred during evolution but so far has received less attention. In this study, its development has been examined morphologically and histologically in the chick, Gallus gallus. Three metatarsal cartilage rods radiating distally earlier in development became aligned parallel to each other by embryonic day 8 (ED8). Calcification initiated at ED8 in the midshaft of cartilage propagated cylindrically along its surface. Coordinated radial growth by fabricating bony struts and trabeculae resulted in the formation of three independent bone cylinders, which further became closely apposed with each other by ED13 when the periosteum began to fuse in a back-to-back orientation. Bone microstructure, especially orientation of intertrabecular channels in which blood vasculature resides, appeared related to the observed rapid longitudinal growth. Differential radial growth was considered to delineate eventual surface configurations of a compound TMT bone, but its morphogenesis preceded the fusion of bone cylinders. Bony trabeculae connecting adjacent cylinders emerged first at ED17 in the dorsal and ventral quarters of intervening tissue at the mid-diaphyseal level. Posthatch TMT skeleton had a seemingly uniform mid-diaphysis, although the septa persisted between original marrow cavities. These findings provide morphological and histological bases for further cellular and molecular studies on this developmental process. Anat Rec 293:1527,1535, 2010. © 2010 Wiley-Liss, Inc. [source]

Insight into Early Pregnancy Events: The Emerging Role of the Embryo,

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 5 2004
Eytan R Barnea
First page of article [source]

Embryonic holoprosencephaly: pathology and phenotypic variability

CONGENITAL ANOMALIES, Issue 4 2006
Shigehito Yamada
ABSTRACT Holoprosencephaly (HPE) is one of the major brain anomalies caused by the failure of cleavage of the prosencephalon during the early stage of development. Over 200 cases of HPE in the Kyoto Collection of Human Embryos were observed grossly and histologically, with special emphasis on the anomalies of the brain, face and eye. The facial anomalies of HPE human embryos after Carnegie stage (CS) 18 could be classified into cyclopia, synophthalmia, ethmocephaly, cebocephaly, and premaxillary agenesis, similarly as the classical classification for postnatal cases. On the other hand, HPE embryos at CS 13,17 showed some characteristic facies which are different from those in older embryos. In the present paper, pathology and phenotypic variability in HPE embryos were discussed from the embryopathological point of view. Recently, the molecular mechanism of HPE has been clarified by the techniques of gene manipulation, and various HPE genes have been identified by gene analysis of familial HPE cases. HPE is one of the major CNS anomalies which have been extensively studied and provides a clue to the mechanisms of normal and abnormal development of craniofacial structures. [source]

Diabetic embryopathy: Studies using a rat embryo culture system and an animal model

CONGENITAL ANOMALIES, Issue 3 2005
Shoichi Akazawa
ABSTRACT The mechanism of diabetic embryopathy was investigated using in vitro experiments in a rat embryo culture system and in streptozotocin-induced diabetic pregnant rats. The energy metabolism in embryos during early organogenesis was characterized by a high rate of glucose utilization and lactic acid production (anaerobic glycolysis). Embryos uninterruptedly underwent glycolysis. When embryos were cultured with hypoglycemic serum, such embryos showed malformations in association with a significant reduction in glycolysis. In a diabetic environment, hyperglycemia caused an increased glucose flux into embryonic cells without a down-regulation of GLUT1 and an increased metabolic overload on mitochondria, leading to an increased formation of reactive oxygen species (ROS). Activation of the hexamine pathway, subsequently occurring with increased protein carbonylation and increased lipid peroxidation, also contributed to the increased generation of ROS. Hyperglycemia also caused a myo-inositol deficiency with a competitive inhibition of ambient glucose, which might have been associated with a diminished phosphoinositide signal transduction. In the presence of low activity of the mitochondrial oxidative glucose metabolism, the ROS scavenging system in the embryo was not sufficiently developed. Diabetes further weakened the antioxidant system, especially, the enzyme for GSH synthesis, ,-GCS, thereby reducing the GSH concentration. GSH depletion also disturbed prostaglandin biosynthesis. An increased formation of ROS in a diminished GSH-dependent antioxidant system may, therefore, play an important role in the development of embryonic malformations in diabetes. [source]

Radiological protection for diagnostic examination of pregnant women

CONGENITAL ANOMALIES, Issue 1 2002
Tomoko Kusama
ABSTRACT, Application of diagnostic X-ray examination to pregnant women is complicated since risks to both mother and embryo/fetus must be considered. Embryos and fetuses are more sensitive to radiation than adults or children. The threshold doses for fetal death, malformations and mental retardation which are deterministic effects, are reported to be 100,200 mGy or higher. The relative risk for childhood cancer due to radiation at an absorbed dose of 10 mGy during embryonic/fetal development has been estimated at 1.4. However, the absorbed dose of the embryo/fetus during X-ray diagnostic examination in which the X-ray beam does not irradiate the embryo/fetus directly such as maternal skull and chest X-ray is extremely low, less than 0.01 mGy. Thus these diagnostic procedures are not a problem from the perspective of radiological protection of the embryo/fetus. However, for pelvic CT scan and barium enema in which the uterus is directly within the X-ray beam, the absorbed doses to the embryo/fetus are about 20,80 mGy and 10,20 mGy, respectively. Therefore, medical staff must pay careful attention to the embryo/fetus in application of these examinations. Pregnant women who were not aware of pregnancy at the time of their diagnostic exposure have great anxiety about radiation from such X-ray examinations. However, fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy. [source]

Vascular endothelial growth factor in edematous mouse embryos induced by retinoic acid in utero

CONGENITAL ANOMALIES, Issue 2 2001
Yoshiko Yasuda
ABSTRACT, Vascular endothelial growth factor (VEGF) is induced by hypoxic environment and contributes to vascular formation in both developing embryos and adults. Exogenous retinoic acid (RA) induces avascular yolk sacs with anemic stunted embryos of day 9 and 10 of gestation when RA is given to pregnant mice on day 6, 6.5 or 7 of pregnancy (Yasuda et al., 1996). We undertook the present studies to find out whether VEGF is activated and plays any role in those RA-exposed embryos. Embryos were obtained from dams given 60 mg/kg of RA on day 6 or 7 of pregnancy and sacrificed three days later. Most RA-exposed embryos showed edematous swelling without prominent vascular nets, but had beating heart tubes on day 9 and day 10 of gestation. Microscopic examination of developing tissue components showed various degrees of degeneration, and distension of the dorsal aorta when the body cavity was dosed. Northern blot analysis revealed expression of VEGF mRNA in the RA-exposed and control embryos. The highest expression of VEGF mRNA was seen in the embryos of day 10 exposed to RA on day 7, and these embryos had a significantly lower ATP content than did the controls (p < 0.01). Immunoreactive VEGF was detectable in both experimental and control embryos; in the former it was especially visible in the distended neuroepithelium, endothelium and membranes. These VEGF-immunoreactive regions also expressed another permeability factor, bradykinin. These findings suggest that VEGF upregulated by hypoxic conditions in edematous embryos induced by RA exposure in utero acts as hyperpermeability. [source]

Visualization of stochastic Ca2+ signals in the formed somites during the early segmentation period in intact, normally developing zebrafish embryos

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 7 2009
Christina F. Leung
Localized Ca2+ signals were consistently visualized in the formed somites of intact zebrafish embryos during the early segmentation period. Unlike the regular process of somitogenesis, these signals were stochastic in nature with respect to time and location. They did, however, occur predominantly at the medial and lateral boundaries within the formed somites. Embryos were treated with modulators of [Ca2+]i to explore the signal generation mechanism and possible developmental function of the stochastic transients. Blocking elements in the phosphoinositol pathway eliminated the stochastic signals but had no obvious effect, stochastic or otherwise, on the formed somites. Such treatments did, however, result in the subsequently formed somites being longer in the mediolateral dimension. Targeted uncaging of buffer (diazo-2) or Ca2+ (NP-ethyleneglycoltetraacetic acid [EGTA]) in the presomitic mesoderm, resulted in a regular mediolateral lengthening and shortening, respectively, of subsequently formed somites. These data suggest a requirement for IP3 receptor-mediated Ca2+ release during convergence cell movements in the presomitic mesoderm, which appears to have a distinct function from that of the IP3 receptor-mediated stochastic Ca2+ signaling in the formed somites. [source]

Effects of prenatal visual stimulation on growth and heart rate in bobwhite quail (Colinus virginianus)

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 4 2006
Merry J. Sleigh
Abstract This study examined the effects of prenatal visual stimulation on bobwhite quail embryos' growth and heart rate. No differences in growth rate were found between embryos exposed to visual stimulation during the late prenatal period and control embryos. Embryos exposed to visual stimulation throughout incubation maintained lower heart rates in response to visual stimulation than did naïve embryos. In a subsequent experiment, naïve embryos that underwent an egg-opening procedure exhibited heart rates that were lower than embryos measured in intact eggshells. Embryos in opened eggs maintained lower heart rates than comparison embryos across time; however, a less invasive egg-opening procedure led to a quicker heart rate recovery than did a more invasive egg-opening procedure. These findings indicate that prenatal heart rate responses may be mediated by multiple features of the organism's developmental context, including intensity and duration of sensory stimulation. © 2006 Wiley Periodicals, Inc. Dev Psyshobiol 48: 315,324, 2006. [source]

An evaluation of the etiology of reduced CYP1A1 messenger RNA expression in the Atlantic tomcod from the Hudson River, New York, USA, using reverse transcriptase polymerase chain reaction analysis

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2001
Nirmal K. Roy
Abstract Adult Atlantic tomcod, Microgadus tomcod, from the Hudson River, New York State, USA, exhibit reduced inducibility of hepatic cytochrome P4501A1 (CYP1A1) mRNA compared with adult tomcod from the cleaner Miramichi River, New Brunswick, Canada, when treated with coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo- p -dioxin. In contrast, little difference in CYP1A1 inducibility is observed between tomcod from these two rivers when treated with polycyclic aromatic hydrocarbons (PAHs). We sought to determine if impaired hepatic CYP1A1 inducibility in Hudson River tomcod results from a multigenerational, genetic adaptation or a single generational, physiological acclimation. Embryos and larvae from controlled experimental crosses of Hudson River and Miramichi River parents were exposed for 24 h to water-borne PCB congener 77 (10 ppm), benzo[a]pyrene (BaP; 10 ppm), or dimethysulfoxide, and CYP1A1 expression was assessed in individual larva using competitive reverse transcriptase polymerase chain reaction (RT-PCR) analysis. The CYP1A1 mRNA was significantly induced in larvae from both populations by BaP (47- and 52-fold) and PCB 77 (9- and 22-fold), although levels of expression were higher in offspring of Miramichi matings. Most important, CYP1A1 mRNA was significantly induced by PCB 77 in larvae from Hudson River parents. Concentrations of dioxin, furan, and PCB congeners were measured in livers and eggs of female tomcod from these two locales to quantify the extent of maternal transfer of contaminants. For both rivers, wet-weight contaminant concentrations were significantly higher (4,7 times) in livers than in eggs of the same females, suggesting that a threshold level of contaminants may have to be reached before CYP1A1 transcription is impaired. We conclude that reduced inducibility of hepatic CYP1A1 mRNA in adult tomcod from the Hudson River is most consistent with single-generational acclimation. [source]

Cellular and molecular basis of cadmium-induced deformities in zebrafish embryos

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000
Shuk Han Cheng
Abstract Cadmium is known to cause developmental defects in a varietyof vertebrate species, but relatively little is known about the underlying molecular mechanisms. In this study, we used zebrafish (Danio rerio) embryos as a model system to investigate cadmium-induced toxicities. Fertilized embryos collected at 5-h after fertilization were incubated for 18 h in culture media containing 1 to 1, 000 ,M CdCl2. The median embryolethal concentration (LC50) was 168 ,M, whereas the median effect concentration (EC50) for total adverse effect (mortality and developmental defects) was 138 ,M. Six major types of deformities were observed: head and eye hypoplasia, hypopigmentation, cardiac edema, yolk sac abnormalities, altered axial curvature, and tail malformations. The frequency of malformations increased with cadmium concentration. Somites of embryos with altered axial curvature were investigated using the antimyosin antibody MF-20. This study demonstrated, to our knowledge for the first time, reduced myotome formation in cadmium-induced spinal deformity. Embryos with head and eye hypoplasia were studied using the anti-neural tissue antibody zns-2, and a poorly developed central nervous system was revealed. Head and eye hypoplasia were associated with lack of expression of the sonic hedgehog gene, which controls the patterning of the neural tube and somites. Genes involved in tail formations, such as evenskipped 1 and no tail, were ectopically expressed in embryos with tail malformations. Our data support the hypothesis that fish embryonic malformations induced by cadmium might be mediated through ectopic expression of developmental regulatory genes. [source]

GEOGRAPHIC VARIATION IN ACID STRESS TOLERANCE OF THE MOOR FROG, RANA ARVALIS.

EVOLUTION, Issue 2 2003

Abstract Spatially varying directional selection together with restricted gene flow among populations is expected to lead to local adaptation. One environmental factor that potentially causes strong directional selection, but is little explored in evolutionary terms, is naturally and anthropogenically induced acidity. We studied local adaptation to acidity in four Swedish populations (two originating from areas that have suffered from severe anthropogenic acidification during the 1900s and two from areas which have remained neutral due to higher buffering capacity) of the moor frog Rana arvalis in a laboratory experiment by investigating whether differences in acid tolerance correspond to population origin. Embryos were raised from fertilization to hatching at three different pH levels (pH 4.0, 4.25 and 7.5), corresponding to levels experienced by these populations in nature, and acid stress tolerance was measured in terms of embryonic survival, hatchling size, and age. Evidence for local adaptation in all of these traits was found, the acid origin embryos having higher survival and less impaired growth performance under acid conditions than the neutral origin embryos. Our estimated rates of divergence (0.007,0.102 haldanes) suggest a rapid adaptation process in response to anthropogenic environmental change, and that the different traits have evolved at relatively similar rates. [source]

Novel regulation of yolk utilization by thyroid hormone in embryos of the direct developing frog Eleutherodactylus coqui

EVOLUTION AND DEVELOPMENT, Issue 5 2010
Srikanth Singamsetty
SUMMARY Thyroid hormone (TH) is required for metamorphosis of the long, coiled tadpole gut into the short frog gut. Eleutherodactylus coqui, a direct developing frog, lacks a tadpole. Its embryonic gut is a miniature adult form with a mass of yolky cells, called nutritional endoderm, attached to the small intestine. We tested the TH requirement for gut development in E. coqui. Inhibition of TH synthesis with methimazole arrested gut development in its embryonic form. Embryos treated with methimazole failed to utilize the yolk in their nutritional endoderm, and survived for weeks without further development. Conversely, methimazole and 3,3,,5-tri-iodo- l -thyronine, the active form of TH, stimulated gut development and utilization and disappearance of the nutritional endoderm. In Xenopus laevis, the receptor for TH, TR,, is upregulated in response to TH. Similarly, EcTR,, the E. coqui ortholog, was upregulated by TH in the gut. EcTR, expression was high in the nutritional endoderm, suggesting a direct role for TH in yolk utilization by these cells. An initial step in the breakdown of yolk in X. laevis is acidification of the yolk platelet. E. coqui embryos in methimazole failed to acidify their yolk platelets, but acidification was stimulated by TH indicating its role in an early step of yolk utilization. In addition to a conserved TH role in gut development, a novel regulatory role for TH in yolk utilization has evolved in these direct developers. [source]

A 49 kDa microtubule cross-linking protein from Artemia franciscana is a coenzyme A-transferase

FEBS JOURNAL, Issue 24 2003
Mindy M. Oulton
Embryos and larvae of the brine shrimp, Artemia franciscana, were shown previously to possess a protein, now termed p49, which cross-links microtubules in vitro. Molecular characteristics of p49 were described, but the protein's identity and its role in the cell were not determined. Degenerate oligonucleotide primers designed on the basis of peptide sequence obtained by Edman degradation during this study were used to generate p49 cDNAs by RT-PCR and these were cloned and sequenced. Comparison with archived sequences revealed that the deduced amino acid sequence of p49 resembled the Drosophila gene product CG7920, as well as related proteins encoded in the genomes of Anopheles and Caenorhabditis. Similar proteins exist in several bacteria but no evident homologues were found in vertebrates and plants, and only very distant homologues resided in yeast. When evolutionary relationships were compared, p49 and the homologues from Drosophila, Anopheles and Caenorhabditis formed a distinct subcluster within phylogenetic trees. Additionally, the predicted secondary structures of p49, 4-hydroxybutyrate CoA-transferase from Clostridium aminobutyricum and glutaconate CoA-transferase from Acidaminococcus fermentans were similar and the enzymes may possess related catalytic mechanisms. The purified Artemia protein exhibited 4-hydroxybutyrate CoA-transferase activity, thereby establishing p49 as the first crustacean CoA-transferase to be characterized. Probing of Western blots with an antibody against p49 revealed a cross-reactive protein in Drosophila that associated with microtubules, but to a lesser extent than did p49 from Artemia. [source]

Molecular characterization of artemin and ferritin from Artemia franciscana

FEBS JOURNAL, Issue 1 2003
Tao Chen
Embryos of the brine shrimp, Artemia franciscana, exhibit remarkable resistance to physiological stress, which is temporally correlated with the presence of two proteins, one a small heat shock/,-crystallin protein termed p26 and the other called artemin, of unknown function. Artemin was sequenced previously by Edman degradation, and its relationship to ferritin, an iron storage protein, established. The isolation from an Artemia expressed sequence tag library of artemin and ferritin cDNAs extends this work. Artemin cDNA was found to contain an ORF of 693 nucleotides, and its deduced amino-acid sequence, except for the initiator methionine, was identical with that determined previously. Ferritin cDNA is 725 bp in length with an ORF of 516 nucleotides. Artemin amino-acid residues 32,185 are most similar to ferritin, but artemin is enriched in cysteines. The abundance of cysteines and their intramolecular spatial distribution suggest that artemin protects embryos against oxidative damage and/or that its function is redox regulated. The conserved regions in artemin and ferritin monomers are structurally similar to one another and both proteins assemble into oligomers. However, modeling of the quaternary structure indicated that artemin multimers lack the central space used for metal storage that characterizes ferritin oligomers, implying different roles for this protein. Probing of Northern blots revealed two artemin transcripts, one of 3.5 kb and another of 2.2 kb. These transcripts decreased in parallel and had almost disappeared by 16 h of development. The ferritin transcript of 0.8 kb increased slightly during reinitiation of development, then declined, and was almost completely gone by 16 h. Clearly, the loss of artemin and ferritin during embryo development is due to transcriptional regulation and proteolytic degradation of the proteins. [source]

Direct DNA delivery into zebrafish embryos employing tissue culture techniques

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 1 2001
Raquel Sussman
Abstract Summary: The production of transfected fish embryos requires expertise in injecting the fertilized eggs and/or expensive equipment for electroporation or microprojectiles. This article demonstrates that by exposure to DNA constructs conjugated with transfecting reagents dechorionated Danio rerio embryos are capable of acquiring extracellular DNA and expressing reporter genes. Embryos incubated with pCMVluc complexed with GeneJammer or GenePORTER expressed luciferase 24,48 h after exposure. pCMVGFP DNA mixed with the same agents generated embryos that exhibited differential patterns of expression of green fluorescent protein (GFP). Embryonic development varied depending on the procedure employed and the reporter gene utilized. Expression of the luciferase gene did not interfere with the subsequent development of the embryos. In contrast, the embryos expressing a high level of GFP were affected, probably due to a very active promoter. These results demonstrate the ease of obtaining transfected fish embryos, which facilitate the mass production of new genotypes and extend the procedure to laboratories with limited resources. genesis 31:1,5, 2001. © 2001 Wiley-Liss, Inc. [source]

Truncation of the MLL gene in exon 5 by gene targeting leads to early preimplantation lethality of homozygous embryos

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 4 2001
Paul Ayton
Abstract Summary: The mixed lineage leukemia gene (MLL) was originally identified through its involvement in reciprocal translocations in leukemias. MLL codes for a large multidomain protein and bears homology to the Drosophila developmental control gene trithorax in two small domains in the amino terminal region, the central zinc finger domain and the carboxy SET domain. Like the Drosophila trx, MLL has also been shown to be a positive regulator of Hox gene expression. We have targeted Mll (the murine homologue of MLL) in exon 5 causing expression of three truncated in-frame Mll transcripts. These transcripts retain all or some of the AT hook motifs and the DMT domain. This mutant allele causes early in vivo preimplantation lethality of homozygous embryos prior to the 2-cell stage. Embryos cultured in vitro progress to the 2-cell stage, but further development is arrested. The heterozygotes exhibit mild skeletal defects as well as defects in some neuroectodermal derivatives. genesis 30:201,212, 2001. © 2001 Wiley-Liss, Inc. [source]