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PubMed2003

Bisphenol A induces apoptosis in central neural cells during early development of Xenopus laevis.

Bisphenol A (BPA), known to be a xenoestrogen, is widely used in industry and dentistry. In the present study, we investigated the effects of BPA on the early development of Xenopus laevis embryos. Stage 6 embryos were exposed to 10-100 microM BPA. Developmental abnormalities were observed when the embryos were exposed to at least 20 microM BPA, with marked developmental abnormalities, such as crooked vertebrae and developmental defects of the head and abdomen, detected in all embryos up to stage 40. Interestingly, apoptosis occurred specifically in central nervous tissue cells of the brain and spinal cord, as assessed by histological analysis. BPA-induced malformations and apoptosis were not observed in embryos exposed to BPA after stage 10. When embryos were exposed to 10 microM 17beta-estradiol (E2), abnormalities were also observed until stage 40. However, the abnormalities induced by BPA and E2 were different and E2 exposure did not induce apoptosis in the central nervous system. Our results indicated that the developmental abnormalities and apoptosis induced by BPA exposure were not inhibited by the addition of E2. In conclusion, we demonstrated that BPA induced marked malformations and specific apoptosis of central nervous system cells during early development of X. laevis embryos, and that these BPA effects appeared to be due to non-estrogenic activities on developmental processes.

Air Pollutants, Occupational↗

PubMed2004

Anomalous origin of the right coronary artery from the left coronary sinus is associated with early development of coronary artery disease.

BACKGROUND: Anomalous origin of the right coronary artery (RCA) from the left coronary sinus can cause sudden cardiac death. Whether this unique anatomical defect also predisposes to early development of coronary artery disease (CAD) remains uncertain. METHODS: Demography, cardiovascular risk factor profiles and coronary angiograms were reviewed in 1,532 consecutive patients over the past 3 years. RESULTS: Thirteen patients (0.8%) had anomalous RCA from the left coronary sinus, while the rest had normal origin from the right coronary sinus. CAD was found in 9/13 anomalous RCA patients (group A) and in 795/1,519 patients with normal RCA origin (group B). There were no differences in the distributions of age, sex or cardiovascular risk factors between the two groups. The distribution of critical lesions among the 3 major coronary arteries showed no significant differences either. However, among the patients with RCA involvement, the anomalous RCA group was significantly younger (54.8 +/- 4.8 years versus 64.9 +/- 10.1 years; p = 0.022). CONCLUSION: The anomalous RCA from left coronary sinus is associated with early development of CAD. The affected patients are 10 years younger.

Aorta↗

PubMed1990

The early development of the tunica media in the vascular system of rat embryos.

The use of a monoclonal antibody (HHF-35) against muscle-cell-specific actin has led to new insights into the early development and differentiation of the tunica media of blood vessels. The localization of this substance was studied by light and electron microscopy, in 22 rat embryos ranging between 10 and 15 days post coitum. Actin expression was already seen in the mesoderm around the dorsal aortae at 10 days post coitum, i.e. 1.5 day before circular mesenchymal condensations were detectable by light microscopy. These condensations are usually regarded as the first indication of arterial tunica media formation. The actin expression starts in the dorso-medial mesoderm surrounding the dorsal aortae at the level of the developing pharyngeal arch system, followed at 11.5 days by positive cells in the lateral mesoderm. In 12-day-old embryos most of the mesenchymal cells around the dorsal aortae contain actin, except for those aspects of the dorsal aortae which participate in outgrowing and connecting vessels to specific organs, such as the pharyngeal arch arteries, dorsal intersegmental arteries and aorto-pulmonary plexus, which themselves are still negative. At this stage the vitelline and umbilical arteries, which belong to the early developing ventral segmental arteries, are already surrounded by actin-containing mesenchymal cells. From 13 days onwards the tributary arteries, such as the subclavian and vertebral arteries, start to present the first differentiation of a tunica media in a proximo-distal development. In general the actin-negative areas are involved in vascular remodelling, implying the formation of new vessels, as as well as the disappearance of those previously developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗

PubMed2005

Translational regulation during oogenesis and early development: the cap-poly(A) tail relationship.

Metazoans rely on the regulated translation of select maternal mRNAs to control oocyte maturation and the initial stages of embryogenesis. These transcripts usually remain silent until their translation is temporally and spatially required during early development. Different translational regulatory mechanisms, varying from cytoplasmic polyadenylation to localization of maternal mRNAs, have evolved to assure coordinated initiation of development. A common feature of these mechanisms is that they share a few key trans-acting factors. Increasing evidence suggest that ubiquitous conserved mRNA-binding factors, including the eukaryotic translation initiation factor 4E (eIF4E) and the cytoplasmic polyadenylation element binding protein (CPEB), interact with cell-specific molecules to accomplish the correct level of translational activity necessary for normal development. Here we review how capping and polyadenylation of mRNAs modulate interaction with multiple regulatory factors, thus controlling translation during oogenesis and early development.

Adenosine↗

PubMed1984

Autoradiographic analysis of cell proliferation and protein synthesis in the pulmonary trunk of rats during the early development of hypoxia-induced pulmonary hypertension.

The results of this study indicate that both cell proliferation and increased synthesis of extracellular matrix protein contribute to hypertrophy of the rat pulmonary trunk during the early development of hypoxia-induced pulmonary hypertension. As determined by autoradiography after 3H-thymidine injection, pulmonary hypertension results in increased labelling in all cell compartments of the pulmonary trunk wall, the most dramatic response occurring in the adventitia following 3 days' hypoxic exposure. Autoradiography also demonstrated differences in the degree of incorporation of 3H-proline into extracellular protein between hypoxic (3 and 21 days) and control rats. The major focus of 3H-proline incorporation shifted from the adventitia at 3 days to the tunica media at 21 days, although incorporation was significantly higher at 3 compared to 21 days in all wall compartments. The patterns of hyperplasia and matrix protein synthesis in the extrapulmonary arteries of the rat, as reported here, are distinctly different from those seen in many large elastic arteries during development of systemic hypertension. For example, the hyperplastic response of arterial vessels follows a similar temporal sequence in pulmonary and systemic hypertension. However, the adventitia is the region of the pulmonary trunk with highest cell proliferation in pulmonary hypertension while the media is most affected by systemic hypertension. The relevance of the changing patterns of cell proliferation and protein synthesis in the wall of the pulmonary trunk of chronically hypoxic rats to the structural and biochemical properties of this vessel during the early development of pulmonary hypertension is discussed.

Animals↗

PubMed2000

Chronic marginal iron intakes during early development in mice alter brain iron concentrations and behavior despite postnatal iron supplementation.

The objective of this study was to investigate the behavioral and cognitive outcomes associated with chronic marginal iron (Fe) intakes during early development. Offspring (3 males and 3 females/litter) of Swiss-Webster female mice who had been fed a control Fe diet (75 microg Fe/g diet) or marginal Fe diet (14 microg Fe/g diet) for 9 wk before mating were weaned on postnatal (PND) 21. Offspring of marginal Fe dams were fed either the marginal Fe diet (marginal group) or a control diet (replete group) from PND 21 throughout the duration of the study, whereas offspring of control dams consumed the control diet ad libitum (control group). On PND 30, 45 and 60, one male and female per litter underwent grip strength and auditory startle testing. A Morris maze was used to assess cognitive function in males starting at PND 50. Marginal Fe mice consistently demonstrated significantly lower grip strength, which was independent of differences in body weight. In addition, marginal Fe males demonstrated attenuated startle responsiveness, as well as altered performance in the Morris water maze. These differences in performance were found in association with lower brain Fe concentrations. Postnatal Fe supplementation did not reverse all of these disturbances because differences in brain Fe concentrations and maze learning persisted. This study demonstrates that chronic marginal Fe intakes during early development can result in persistent biochemical and behavioral changes in mice.

Animals↗

PubMed1992

Changes in whole body concentrations of cortisol, thyroid hormones, and sex steroids during early development of the chum salmon, Oncorhynchus keta.

Significant amounts of cortisol (20 ng/g) and thyroid hormones thyroxine (T4, 20 ng/g) and triiodothyronine (T3, 10 ng/g), as well as estradiol (8 ng/g) and testosterone (4 ng/g), are present in fertilized eggs of chum salmon. Changes in the concentrations of these hormones in the developing embryo and larvae were monitored until after the emergence of the fry from the gravel bed. Cortisol concentrations in the developing embryo fell steadily from 20 ng/g at fertilization to 2.5 ng/g after 3 weeks, increased slightly to 10 ng/g by 1 week before hatching, and maintained this level during the early stages of yolk sac absorption. During the later stages of yolk sac absorption, cortisol concentrations increased markedly and remained at about 30 ng/g until emergence, when they declined to 10-15 ng/g. In contrast, both T4 and T3 levels were stable during early development, decreased gradually during yolk sac absorption, and increased slightly during emergence. Estradiol and testosterone profiles were similar to that of cortisol during early development. Testosterone levels remained low throughout emergence. Likewise, estradiol levels were low during yolk sac absorption but showed a transient increase at the time of emergence. These hormonal changes are discussed in the context of egg development and subsequent downstream migration.

Animals↗

PubMed1990

Optical studies of early developing cardiac and neural activities using voltage-sensitive dyes.

Using optical methods for monitoring cellular electrical activity based on voltage-sensitive dyes, we have overcome several obstacles to the study of electrical function in the embryonic heart and central nervous system during early development. We have been able to monitor, for the first time, spontaneous electrical activity in the pre-fused cardiac primordia in early chick embryos at the 6- and early 7-somite stages of development and to follow the early development of electrical activity in the pre-contractile heart at the 7- to 9-somite stages. In addition, we have monitored neural responses in the early embryonic chick brain stem by optical means, and determined the spatial pattern of the response.

Action Potentials↗

PubMed1990

Expression of the N-myc proto-oncogene during the early development of Xenopus laevis.

The N-myc proto-oncogene is expressed in a wide range of tissues during mammalian embryogenesis. This observation, along with the oncogenic capacity of this gene, has led to the suggestion that N-myc plays an important role in early development. However, due to the complexity of the expression pattern and the difficulty of manipulating mammalian embryos, little progress has been made towards understanding the developmental function of this gene. To enable a more detailed analysis of the role of this gene in early development, a study of the Xenopus homologue of N-myc was undertaken. Xenopus N-myc cDNA clones were isolated from a neurula library using a murine N-myc probe. Analysis of the timing of expression of N-myc mRNA and of the distribution of N-myc protein during Xenopus development indicate that this gene may be playing an important role in the formation of a number of embryonic structures, including the nervous system. N-myc is initially expressed as a maternal RNA, but this mRNA is degraded by the gastrula stage of development. Zygotic expression does not commence until late neurula. Examination of the distribution of the N-myc protein by whole-mount immunohistochemistry indicates that the early embryonic expression occurs in the central nervous system, the neural crest, the somites and the epidermis. Later expression is mostly within the head and somites. Specific structures within the head that express the protein include the eye, otic vesicle, fore and hindbrain and a number of cranial nerves. The results demonstrate that while N-myc is expressed in the developing nervous system of Xenopus, the timing of expression indicates that it is unlikely to be involved in regulation of the very first stages of neurogenesis.

Animals↗

PubMed2004

G1/S phase cyclin-dependent kinase overexpression perturbs early development and delays tissue-specific differentiation in Xenopus.

Cell division and differentiation are largely incompatible but the molecular links between the two processes are poorly understood. Here, we overexpress G1/S phase cyclins and cyclin-dependent kinases in Xenopus embryos to determine their effect on early development and differentiation. Overexpression of cyclin E prior to the midblastula transition (MBT), with or without cdk2, results in a loss of nuclear DNA and subsequent apoptosis at early gastrula stages. By contrast, overexpressed cyclin A2 protein does not affect early development and, when stabilised by binding to cdk2, persists to tailbud stages. Overexpression of cyclin A2/cdk2 in post-MBT embryos results in increased proliferation specifically in the epidermis with concomitant disruption of skin architecture and delay in differentiation. Moreover, ectopic cyclin A2/cdk2 also inhibits differentiation of primary neurons but does not affect muscle. Thus, overexpression of a single G1/S phase cyclin/cdk pair disrupts the balance between division and differentiation in the early vertebrate embryo in a tissue-specific manner.

Animals↗

PubMed2002

Control of poly(A) polymerase level is essential to cytoplasmic polyadenylation and early development in Drosophila.

Poly(A) polymerase (PAP) has a role in two processes, polyadenylation of mRNA precursors in the nucleus and translational control of certain mRNAs by cytoplasmic elongation of their poly(A) tails, particularly during early development. It was found recently that at least three different PAP genes exist in mammals, encoding several PAP isoforms. The in vivo specificity of function of each PAP isoform currently is unknown. Here, we analyse PAP function in Drosophila: We show that a single PAP isoform exists in Drosophila that is encoded by the hiiragi gene. This single Drosophila PAP is active in specific polyadenylation in vitro and is involved in both nuclear and cytoplasmic polyadenylation in vivo. Therefore, the same PAP can be responsible for both processes. In addition, in vivo overexpression of PAP does not affect poly(A) tail length during nuclear polyadenylation, but leads to a dramatic elongation of poly(A) tails and a loss of specificity during cytoplasmic polyadenylation, resulting in embryonic lethality. This demonstrates that regulation of the PAP level is essential for controlled cytoplasmic polyadenylation and early development.

Animals↗

PubMed2006

Dynamic changes in microtubules and early development of reconstructed embryos after somatic cell nuclear transfer in a non-human primate.

In order to improve somatic cell nuclear transfer (SCNT) efficiency and to understand cellular changes in SCNT, the dynamic changes in microtubules/DNA and early development of SCNT embryos with single or multiple pronuclei were investigated, along with activation timing on efficiency of SCNT, were studied in the Cynomolgus monkey. The confocal images showed that microtubules assembled around condensed DNA at 1h after cell injection; normal or abnormal reconstructed spindle formed at 2 h after cell injection; and reconstructed spindle separated at 2 h after activation. The results of nuclear formation showed that 61.3% of the reconstructed embryos did not form pronuclei; 19.3% formed a single nucleus, and 11.9% and 7.5% formed two and more than two reconstructed pronuclei, respectively. The cleavage and 8-cell development rates of SCNT embryos with pronuclei were significantly higher than those without pronuclei, but there was no difference in development rates among NT embryos with single, two and more then two pronuclei. Activation at 2 h after cell injection yielded more embryos with pronuclei and yielded 8-cell NT embryos more reliably than did activation at 3-4 h. In conclusion, microtubules assembled around condensed DNA at 1-2 h after cell injection, and formed a spindle at 2 h after SCNT, which separated at 2 h after activation; early development was affected by activation time, but no different between single and multiple pronuclei.

Animals↗

PubMed2005

Early development of the facial region in a non-avian theropod dinosaur.

An isolated maxilla of the theropod dinosaur Allosaurus from the Late Jurassic (the Kimmeridgian, 153 million years ago) of Portugal is the first cranial remain of a non-coelurosaurian theropod hatchling reported so far, and sheds new light on the early cranial development of non-avian theropods. Allosaurus hatchlings seem to have been one-seventh or less of the adult length and are thus comparable in relative size to hatchlings of large extant crocodile species, but are unlike the relatively larger hatchlings in coelurosaurs. The snout experienced considerable positive allometry and an increase in tooth count during early development. The element is especially noteworthy for the abundant and well-developed features associated with the paranasal pneumatic system. Pneumatic structures present include all those found in adult allosaurids and most are even more developed than in adult skulls. Together with evidence on the ontogeny of the tympanic pneumatic system in allosaurids, these findings demonstrate that cranial pneumaticity developed early in theropod ontogeny. The strong development of pneumatic features in early ontogenetic stages of non-avian theropods supports the hypothesis that pneumatization of cranial bones was opportunistic and indicates that heterochrony played an important role in the evolution of craniofacial pneumaticity in this group.

Animals↗

PubMed2000

Distribution of fibrillin I in extracellular matrix and epithelia during early development of avian embryos.

Fibrillin microfibrils are widely distributed components of extracellular matrices that function in the formation of elastin, serve structural roles and provide substrates for cell adhesion. To determine when and how fibrillin-1 (fib-1) may function in early development we have examined the temporal and spatial distribution of fib-1 in chicken embryos. Using homologous PCR we amplified and cloned a 407 nt fragment of chicken cDNA that appears to code for an orthologue of FBN-1. Bacterially expressed protein was used to prepare two monoclonal antibodies, both of which recognize a 350 kD band in immunoblots or immunoprecipitates in supernatants of chicken embryonic aorta cells or human MG-63 cells. Both antibodies recognize fibrillar material associated with the surfaces of cultured cells. The antibodies appear to be specific for fib- as there was only weak cross reactivity to a bacterially expressed fragment from the corresponding region of fib-2 and the pattern of immunofluorescence in embryonic tissue is distinctly different from that of JB-3, a fib-2 specific antibody (Rongish et al. 1998). In embryos, fib-1 is first detected at stage 6 in the epiblast during gastrulation. In subsequent stages fib-1 fibers appear in all tissues and are present throughout the first 6 days of development. Immunoreactive fibers are present in basal laminae and mesenchyme filled spaces, but they also form random arrays with an apical-basal polarity within epithelia. Using primers specific for FBN-1 and FBN-2 in RT-PCR reactions we confirm the presence of fib- 1 and fib-2 mRNA in early embryonic stages. This temporal and spatial distribution indicates fib-1 has functions in early development that are distinct from fib-2.

Amino Acid Sequence↗

PubMed1987

Mapping of early development of electrical activity in the embryonic chick heart using multiple-site optical recording.

1. Using a multiple-site optical recording method with a 100-element photodiode array and a voltage-sensitive merocyanine-rhodanine dye, we have been able to monitor, for the first time, spontaneous electrical activity in pre-fused cardiac primordia in the 6- and 7-somite chick embryos. 2. To study the regional development of spontaneous electrical activity in the early embryonic pre-contractile chick heart at the later 7-9-somite stages, we have also recorded optically action potentials simultaneously from the entire heart, and constructed maps of the early development of electrical activity. 3. The data show that during the 6-9-somite stages, the size of the active area gradually increases, and that the development of electrical activity was spatially non-uniform: two peaks of activity were found in the right and left sides of the cono-ventricular region at the 7-8-somite stages. As development proceeded to the 9-somite stage, several peak areas of activity appeared. 4. The results are discussed in relation to the spatial pattern of proliferation of electrically active cells in the early phases of cardiogenesis.

Action Potentials↗

PubMed1995

Poly (A) polymerases in the nucleus and cytoplasm of frog oocytes: dynamic changes during oocyte maturation and early development.

Poly(A) can be added to mRNAs both in the nucleus and in the cytoplasm. During oocyte maturation and early embryonic development, cytoplasmic polyadenylation of preexisting mRNAs provides a common mechanism of translational control. In this report, to begin to understand the regulation of polyadenylation activities during early development, we analyze poly (A) polymerases (PAPs) in oocytes and early embryos of the frog, Xenopus laevis. We have cloned and sequenced a PAP cDNA that corresponds to a maternal mRNA present in frog oocytes. This PAP is similar in size and sequence to mammalian nuclear PAPs. By immunoblotting using monoclonal antibodies raised against human PAP, we demonstrate that oocytes contain multiple forms of PAP that display different electrophoretic mobilities. The oocyte nucleus contains primarily the slower migrating forms of PAP, whereas the cytoplasm contains primarily the faster migrating species. The nuclear forms of PAP are phosphorylated, accounting for their retarded mobility. During oocyte maturation and early postfertilization development, preexisting PAPs undergo regulated phosphorylation and dephosphorylation events. Using the cloned PAP cDNA, we demonstrate that the complex changes in PAP forms seen during oocyte maturation may be due to modifications of a single polypeptide. These results demonstrate that the oocyte contains a cytoplasmic polymerase closely related to the nuclear enzyme and suggest models for how its activity may be regulated during early development.

Amino Acid Sequence↗

PubMed1994

cdc2 kinase sets a memory phosphorylation signal on elongation factor EF-1 delta during meiotic cell division, which perdures in early development.

EF-1 delta is a physiological substrate for cdc2 protein kinase in Xenopus oocytes. The protein is part of the nucleotide exchange factor EF-1 beta gamma delta, involved in the elongation step of protein synthesis. We show that EF-1 delta exists under four isoforms in the prophase oocyte, all phosphorylable by casein kinase II. Each of the prophase isoforms was further separated into a 36 and a 38 kDa form upon phosphorylation by cdc2 kinase which therefore reveals the existence of eight different isoforms. Phosphorylation by cdc2 kinase can be monitored as the electrophoretic mobility dedoublement 36/38 kDa. Developmental regulation of EF-1 delta was analyzed. The cdc2 kinase-induced change occures at meiotic division, after complete oogenesis and perdures during early development. It is therefore a phosphorylation memory signal for early development.

Animals↗

PubMed1984

Early development of descending pathways from the brain stem to the spinal cord in Xenopus laevis.

The early development of descending pathways from the brain stem to the spinal cord has been studied in Xenopus laevis tadpoles. The relatively protracted development of this permanently aquatic amphibian as well as its transparency during development make this animal particularly attractive for experimental studies. Between the 5th and 10th myotome the spinal cord was crushed with a thin needle and dry horseradish peroxidase (HRP) crystals were applied. After a survival time of one day the tadpoles were fixed and the brain and spinal cord were stained as a whole according to a modification of the heavy metal intensification of the DAB-reaction, cleared in cedarwood oil and examined as wholemounts. At stage 28 (the neural tube has just closed) the first brain stem neurons projecting to the spinal cord were found in what appear to be the nucleus reticularis inferior and -medius. At this stage of development the first, uncoordinated swimming movements can be observed. At stage 30/31 (the tailbud is visible) both Mauthner cells project to the spinal cord as well as the interstitial nucleus of the fasciculus longitudinalis medialis situated in the mesencephalon. Towards stage 35/36 (the tail is now clearly visible), a more extensive reticulospinal innervation of the spinal cord appears, now including cells of the nucleus reticularis superior. At this stage also the first vestibulospinal and raphespinal projections were found. At stage 43/44 (the tadpoles have now a well-developed tail) the pattern of reticulospinal projections appears to be completed with the presence of labeled neurons in the nucleus reticularis isthmi. From stage 43/44 on, the number of HRP-positive cells is steadily increasing. At stage 47/48, when the hindlimb buds appear, the descending projections to the spinal cord are comparable with the adult situation except for the absence of a rubrospinal and a hypothalamospinal projection. The observations demonstrate that already very early in development reticulospinal fibers and, somewhat later, Mauthner cell axons and vestibulospinal fibers innervate the spinal cord. Furthermore, a caudorostral gradient appears to exist with regard to the development of descending projections to the spinal cord. However, the interstitial nucleus of the fasciculus longitudinalis medialis forms an exception to this rule.

Animals↗