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PubMed2001

Expression of Xenopus L-arginine:glycine amidinotransferase (XAT) during early embryonic development.

We have isolated a full-length cDNA encoding Xenopus L-arginine:glycine amidinotransferase (XAT), which shares a highly conserved sequence with human, chick and rat amidinotransferase. Although there are some studies about its structure and function in energy metabolism of adult tissues in some other species, little is known about its roles during early embryonic development. Characterization of embryonic expression indicates that XAT is differentially expressed around the yolk plug including the dorsal blastopore area at early gastrula stages and is extensively expressed in the midline of the neural plate of early neurula stages. Sections reveal that its transcripts are located in the notochord. In the tailbud stage signals are found both in the notochord and trunk area, whereas only faint signals can be found in the cephalic part.

Amidinotransferases↗
PubMed1997

Maternal thyroid hormones in Japanese quail eggs and their influence on embryonic development.

We addressed the relationship between the thyroid status of hens and the thyroid hormone content of their eggs, as well as the influences of egg hormones on embryonic development. Methods for measuring thyroid hormones in egg yolk were verified by demonstrating consistency in the recovery of yolk thyroid hormones following a methanol/chloroform extraction and in the measurement of thyroid hormones by RIA for a range of hormone concentrations in yolk extracts. Untreated hens produced eggs with yolk thyroxine (T4) concentrations that were low relative to plasma T4, but yolk triiodothyronine (T3) concentrations comparable to those of plasma. Hens dosed twice daily with T4 (1 or 3x the daily thyroid secretion rate, TSR, of T4 per dose) had significantly higher plasma and egg yolk T4 concentrations than did control hens dosed with saline. In general, the T4 concentration of egg yolk varied with the thyroid status of the hen. When the relationship between each hen's plasma T4 and the yolk T4 concentration of her eggs was examined, hens appeared to regulate T4 deposition into yolk at "levels" characteristic of the "levels" of thyroid status produced by the different doses of T4. Embryonic pelvic cartilage, a thyroid hormone-responsive tissue, showed enhanced growth and differentiation in embryos from eggs of hens given the highest dose of T4. Specifically, alkaline phosphatase activity (a marker of differentiation) and pelvic cartilage wet and dry weights were significantly greater in embryos from high T4 eggs (hens on the 3x TSR dose) than those in controls. However, embryos from high T4 eggs did not differ in general body growth (body weight, length, and general morphology) or hatchability compared to controls. In a single T3 experiment, hens were dosed twice daily with 1 microg T3. The embryos from eggs of these hens had accelerated differentiation/maturation of pelvic cartilages (sampled at Day 12) compared to those from control eggs; body growth did not differ from that of controls.

Animals↗
PubMed1990

Transcription of endogenous and injected cytoskeletal actin genes during early embryonic development in Xenopus laevis.

The transcriptional regulation of a cytoskeletal actin gene during Xenopus laevis embryonic development has been investigated. New transcripts of this gene begin to accumulate at approximately the mid-gastrula stage, between 12 and 16 hours after fertilization, replenishing maternal supplies of this transcript. To study the molecular processes which act to determine the timing of transcriptional activation of this gene, a gene-injection assay was devised, utilizing a cloned copy of the gene which has been marked by a small DNA insertion. Accurately-initiated transcripts of the injected gene accumulate in concert with those of the endogenous gene, showing that injected genes can undergo developmental regulation. As little as 485 nucleotides of upstream sequence is sufficient for proper temporal control of activation of an injected gene. The results presented here demonstrate the feasibility of a microinjection assay for the identification of regulatory gene sequences and transacting regulatory factors in amphibian embryos. Such an assay will be useful in achieving an understanding of general transcriptional control mechanisms acting in early development, and should also provide a means to study certain aspects of long-standing developmental problems, such as cytoplasmic localization and embryonic induction.

Actins↗
PubMed1987

Changes in cyclic nucleotide levels during embryonic development of chick hearts.

The effects of isoproterenol, acetylcholine (Ach), and adenosine, on cyclic AMP (cAMP) and cyclic GMP (cGMP) contents were examined in chick hearts at various stages of embryonic development. The basal cAMP content was highest (87.7 +/- 1.3 pmol/mg protein) in young (3-day) embryonic chick hearts and decreased during development (9.6 +/- 0.6 pmol/mg protein in 9-19-day-old hearts). On the other hand, the cGMP content was lowest (45.5 +/- 2.3 fmol/mg protein) in young (3-day) embryonic chick hearts and increased during development (338 +/- 15.0 fmol/mg protein in 14-19-day-old hearts). Iso increased the cAMP concentration in embryonic hearts at all ages. Ach and Ado had no effect on the cAMP content at all ages. However, the Isoproterenol-induced stimulation of cAMP was inhibited by Ach and Adenosine at all ages. In young embryonic hearts, Ach and Ado increased cGMP concentration only slightly, whereas these agents caused a substantial increase in cGMP concentration in the older hearts. Thus, there was a clear age difference in the effects of Ach and Adenosine on the cGMP and cAMP concentrations. Nitroprusside and hydrogen peroxide increased cGMP concentration in older hearts (greater than 5-day-old) but not in the 3-day-old embryonic hearts. Thus, guanylate cyclase activity may be low in young (3-day-old) hearts. It summary, the cGMP level is very low in young embryonic chick hearts, and increases markedly during development. The changes in cGMP are reciprocal to those of cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1997

Differential expression patterns of the PEA3 group transcription factors through murine embryonic development.

ERM, ER81 and PEA3 are three highly related transcription factors belonging to the ETS family. Together they form the PEA3 group within this family. Little data is yet available regarding the roles of these three genes during embryonic development. A prerequisite to investigations in this field is to obtain an accurate spatio-temporal expression map for the erm, er81 and pea3 genes. To this end, we have used in situ hybridization to compare their expression patterns during critical stages of murine embryogenesis. We report that all three genes are expressed in numerous developing organs coming from different embryonic tissues. The three genes appeared co-expressed in different organs but presented specific sites of expression, so that the resultant expression pattern could in fact reveal several distinct functions depending upon isolated and/or various combinations of the PEA3 member expression. These results suggest that erm, er81 and pea3 genes are differentially regulated, probably to serve important functions as cell proliferation control, tissue interaction mediator or cell differentiation, all over successive steps of the mouse organogenesis.

Amino Acid Sequence↗
PubMed1999

Induction of somatotroph differentiation in vivo by corticosterone administration during chicken embryonic development.

Somatotroph differentiation in the embryonic pituitary of avian and mammalian species can be stimulated by glucocorticoids in vitro, and this effect can be augmented by concomitant treatment with growth hormone-releasing hormone (GHRH). Owing to its isolation from maternal influences, the chick embryo is a useful model for studying humoral regulation of pituitary cell differentiation. Somatotroph differentiation in chickens occurs between embryonic day (e-) 14 and e-16, and treatment of e-12 pituitary cells with e-16 serum or corticosterone induces growth hormone (GH) cell differentiation within 2 d in culture. The objective of the present study was to determine whether direct administration of embryonic serum and corticosterone to developing chick embryos was effective in vivo in inducing somatotroph differentiation prematurely. The albumen of fertile eggs was injected on e-11 with 300 approximately microL of 0.9% saline or 150 microL of serum from e-12 or e-16 chick embryos diluted 1:1 with saline. The embryos were allowed to develop until e-14, when pituitaries were dispersed and the resulting pituitary cells were subjected to reverse hemolytic plaque assays (RHPA) and immunocytochemistry to detect GH-secreting and GH-containing cells, respectively. Injection of e-16 serum increased (p < 0.01) GH-secreting and GH-containing cells to 11.5 +/- 1.0% and 1 7.4 +/- 3.3% of all pituitary cells, compared to 5.0 +/- 0.3% and 5.5 +/- 0.9% for saline-injected controls, respectively. Day 12 serum increased GH-containing cells to 9.8 +/- 0.9%, without changing percentages of GH-secreting cells. In experiment 2, saline, e-16 serum, and corticosterone were injected on e-11, and pituitary cells were subjected to GH RHPA on e-14. GH secretors were increased by e-16 serum and corticosterone. In experiment 3, we tested whether GHRH would magnify the effect of corticosterone, as we had seen in extended 6-d cultures previously. Saline, corticosterone, and corticosterone plus GHRH were injected on e-11, and pituitary cells were subjected to GH RHPA on e-18. Treatment with corticosterone alone and combined with GHRH increased the percentage of GH-secreting cells. However, combined treatment with corticosterone and GHRH was not more effective than corticosterone alone. The present findings demonstrate that glucocorticoid administration can stimulate somatotroph differentiation in living vertebrate embryos isolated from maternal interactions.

Animals↗
PubMed2005

Nucleocytoplasmic ratio of fully grown germinal vesicle oocytes is essential for mouse meiotic chromosome segregation and alignment, spindle shape and early embryonic development.

BACKGROUND: This study examined the effect of nucleocytoplasmic ratio of fully grown germinal vesicle (GV) oocytes on meiotic chromosome segregation and alignment, spindle shape, Ca(2+) oscillations and capacity of early embryonic development in mouse. METHODS: GV oocytes with reduced volume (equal to 1/5 to 4/5 of an intact oocyte) were made by micromanipulation to remove different amounts of cytoplasm, and then matured and fertilized in vitro. RESULTS: When >1/2 of GV oocyte cytoplasm was removed, the time-course of GV breakdown (GVBD) was delayed and oocyte maturation rate decreased significantly. Abnormal chromosome segregation rate increased if >1/2 of the cytoplasm was removed from the oocyte. Length and structure of meiotic spindle and chromosome alignment were also impaired by the reduction of cytoplasmic volume. Once matured in vitro, the oocytes could undergo Sr(2+)-induced Ca(2+) oscillations and form pronuclei in a manner independent of nucleocytoplasmic ratio, but their ability to develop to 2-cell embryos was affected if >1/2 of their cytoplasm was removed from the GV oocytes. CONCLUSIONS: These results suggest that nucleocytoplasmic ratio is essential for normal meiotic chromosome segregation, spindle formation and chromosome alignment over the metaphase spindle, and development to 2-cell stage, for which 1/2 of the volume of the GV oocyte appears to be a threshold.

Animals↗
PubMed2000

Ontogeny of corticosterone-inducible growth hormone-secreting cells during chick embryonic development.

We reported that corticosterone administration into the albumen of fertile chicken eggs on embryonic day (e) 11 induces an increase in the population of GH-secreting cells. The present study evaluated the ontogeny, dose response, localization, and persistence of the glucocorticoid-induced increase in the somatotroph population during chicken embryonic development. Corticosterone (0, 0.02, 0.2, and 2 microg in 300 microl saline) was injected into separate eggs on e9, e10, e11, and e12, and the population of GH-secreting cells was assessed 2 days later using reverse hemolytic plaque assays. Corticosterone treatment on e9 or e10 was unable to increase the population of GH-secreting cells on e11 or e12. In contrast, 0.2 and 2 microg of corticosterone on e11 increased the population of GH-secreting cells on e13 (P < 0.05, n = 3 experiments) to 8.2 +/- 0.6 and 6.4 +/- 0.5% of all cells, respectively, relative to controls (2.4 +/- 0.2%). For e14 embryos treated on e12, only the 2 microg dose increased the proportion of GH-secreting cells (6.4 +/- 0.6%) relative to controls (3.6 +/- 0.4%). In a second experiment, 0, 0.02, 0.2, 2, and 20 microg of corticosterone were injected on e0, e8, e9, e10, e11, and e12, and the population of GH-secreting cells was assessed on e13 in all groups. No dose of corticosterone was effective when given on e0, e8, e9, or e10. The 0.2 microg and 2 microg doses increased the population of GH-secreting cells (7.6 +/- 0.9% and 6.7 +/- 0.8%, respectively) relative to controls (2.3 +/- 0.4%) when injected on e11 (P < 0.05, n = 4 experiments). The 2-microg dose also increased GH cell abundance when injected on e12 (5.6 +/- 0.4%), relative to controls (2.7 +/- 0.5%). Treatment with 20 microg on e11 and e12 induced the greatest responses (10.3 +/- 1.1% and 8.7 +/- 0.9%, respectively). However, in subsequent experiments, administration of 20 microg on e11 resulted in embryonic death by e18. In a third set of experiments, two groups of eggs were injected either with 2 microg of corticosterone in saline or saline alone on e11, and the number of GH-secreting cells was estimated on e13, e16, e19, and the day of hatch (d1). The population of GH-secreting cells in corticosterone treated embryos was significantly higher than in saline treated embryos only on e13 (7.1 +/- 0.8% and 2.7 +/- 0.3%, respectively). No significant differences were observed on e16 (12.4 +/- 1.5% and 13.6 +/- 1.2%), e19 (19.0 +/- 1.0% and 18.2 +/- 1.7%) and d1 (23.8 +/- 2.1% and 25.1 +/- 1.8%) between corticosterone treated and control embryos, respectively. In a fourth set of experiments, whole mount in situ hybridization indicated that injection of corticosterone on e11 induced GH messenger RNA expression in the caudal part of the pituitary gland on e13, where somatotrophs are located normally later in development. We conclude that corticosterone administration in ovo can increase the population of GH-secreting cells in the caudal anterior pituitary only during a small window of development between e11 and e13 and that this premature increase of GH-secreting cells does not affect the percentage of GH-secreting cells later in development.

Animals↗
PubMed1994

Early expression of the KAL gene during embryonic development of the chick.

The human KAL gene is responsible for the X chromosome-linked Kallmann syndrome, which consists of the association of hypogonadotropic hypogonadism and anosmia. The human and chicken KAL genes have been isolated. Using in situ hybridization, we studied KAL gene expression during development of the chick. We have previously reported that, from embryonic day 8, the expression is almost restricted to definite neuronal populations in the central nervous system, most of which still express the gene after hatching. Here we report that the KAL gene is also expressed during early embryonic development (days 2-8) in various endodermal, mesodermal, and neurectodermal derivatives. In most endodermal and mesodermal derivatives, the expression is transient and precedes cell differentiation. In contrast, the expression in the nervous system concerns postmitotic central neuroblastic populations, most of which still express the gene after differentiation. In accordance with such a spatio-temporal pattern of expression, we suggest that the KAL gene is involved both in morphogenetic events and in neuronal late differentiation. In addition, the absence of detectable expression of the KAL gene either in the embryonic olfactory epithelium or in the surrounding nasal mesenchyme reinforces the hypothesis that Kallmann's syndrome results from a central olfactory target cell defect.

Animals↗
PubMed2005

MicroRNA expression in zebrafish embryonic development.

MicroRNAs (miRNAs) are small noncoding RNAs, about 21 nucleotides in length, that can regulate gene expression by base-pairing to partially complementary mRNAs. Regulation by miRNAs can play essential roles in embryonic development. We determined the temporal and spatial expression patterns of 115 conserved vertebrate miRNAs in zebrafish embryos by microarrays and by in situ hybridizations, using locked-nucleic acid-modified oligonucleotide probes. Most miRNAs were expressed in a highly tissue-specific manner during segmentation and later stages, but not early in development, which suggests that their role is not in tissue fate establishment but in differentiation or maintenance of tissue identity.

Animals↗
PubMed1992

Structural and functional post-embryonic development of a non-rectifying electrical synapse in the crayfish.

The post-embryonic development of the non-rectifying septate synapse between homologous lateral giant (LG) fibre segments has been investigated using electron microscopy and electrophysiology. In adults, the LG-LG synapse is characterized by closely apposed membranes (approximately 4 nm separation) traversed by regularly spaced particles, and large (60-80 nm) spherical vesicles on both sides of the junction. In newly hatched crayfish the junction between lateral giant fibre segments comprises regions of close membrane apposition as seen in the adult along with non-specialized areas of wide (10-15 nm) membrane separation. Vesicles associated with these junctions are small (25-40 nm) and pleomorphic. The number of vesicles is low by comparison with adult junctions; in most sections of hatchling junctions there are normally fewer than five vesicles, although as many as 30 have occasionally been seen. During development the non-specialized areas of wide membrane separation become rare and the vesicle population changes to a mixture of small pleomorphic forms and larger (60-80 nm) spherical ones. However even at two months the number of large spherical vesicles is markedly less than that at the adult synapse, while small pleomorphic vesicles are still abundant. Despite the difference between the adult and hatchling vesicle populations, intracellular recordings have shown that the synapse is fully functional as a non-rectifying electrical junction on hatching and that the intracellular marker Lucifer Yellow can pass between adjacent lateral giant fibre neurons.

Animals↗
PubMed1985

Nuclear ADP-ribosylation in the chick lens during embryonic development.

Nuclear ADP-ribosyltransferase is present in cells from the chick lens throughout embryonic development. The activity does not decrease when the cells become post-mitotic and commence terminal differentiation but declines slowly in both epithelia and fibre cells. At all stages studied the enzyme retains its ability to be activated by DNA strand breaks induced either by X-irradiation or by the action of an endogenous endonuclease. There is no correlation between the enzyme activity or the levels of its substrate NAD+ and the changes in DNA repair capacity which have been observed during the development of the lens.

Animals↗
PubMed1994

Acetylcholine receptor and myogenic factor gene expression in Torpedo embryonic development.

The mRNA levels of acetylcholine receptor (AChR) and myogenic factors were followed during embryonic development of Torpedo skeletal muscle and its homologue, the electric organ. A different developmental pattern of AChR gene expression was found in these two tissues: a slight decrease in the muscle, and a marked increase, concomitant with synapse formation, in the electric organ. However, the developmental pattern of MyoD and MRF4 mRNA levels was similar in both tissues, with no significant changes during development. This is in contrast with the sharp increase in the expression of AChR in the electric organ and may suggest that the burst in the expression of AChR during the differentiation of myotubes into electrocytes is not regulated by changes in the myogenic factor mRNA levels.

Animals↗
PubMed1998

Embryonic development of the inner ear and otolith of the rainbow trout Oncorhynchus mykiss.

The embryonic development of the inner ear, especially the sensory epithelia and otoliths in the rainbow trout Oncorhynchus mykiss, was studied by light and electron microscopy. Light microscopically, the auditory vesicle, saccular otolith and statoacoustic ganglion were first observed by 12 days after fertilization, while the utricular otolith appeared at 15 days after fertilization. Both the saccular and utricular maculae were more developed at 22 days after fertilization, and well developed by 27 days. The crista ampullaris of the horizontal canal was also developed at 27 days after fertilization, while the other cristae were not yet distinguished. Electron microscopically, vesicular structures and short microvilli were found on the sensory epithelia of the maculae by 15 days after fertilization. At 22 days after fertilization, the saccular otolith possessed 7 incremental layers, and developing cilia, microvilli, and aggregates of secretory materials also appeared on the apical surface of the sensory epithelia. At 27 days after fertilization, the apical surface of each hair cell was covered with a hair bundle consisting of a single kinocilium and a bundle of stereocilia. These findings are discussed with special regard to the environmental factors on early development in fishes.

Animals↗
PubMed2001

Embryonic development of the freshwater snail Biomphalaria glabrata under microgravity conditions (STS-89 mission).

The embryonic development of the fresh-water snail Biomphalaria glabrata was examined under microgravity-conditions and compared with the ground control and standard embryos, putting special emphasis on the shell formation. The process of shell formation may be particularly sensitive to the change of gravitational forces. The project aimed at determining whether the processes of mineralization during the formation of the exoskeleton in the growing snail embryo take place normally under microgravity conditions. Twenty-four adult individuals of the tropical freshwater snail B. glabrata were maintained 9 days in the Closed Equilibrated Biological Aquatic System (CEBAS Minimodule) on Space Shuttle flight STS-89. The animals produced spawning packs throughout the duration of the mission so that embryos of all developmental stages were achieved. The embryos developed slightly slower in the CEBAS than under standard conditions, and in older embryos a decreased mineralization of the shell was detected. These phenomena, however, were observed in the flight module as well as in the ground control specimens and was not an effect caused by the microgravity conditions. Embryos of B. glabrata showed a correct morphogenesis under microgravity, no teratological effects were noticed, and the shell formation proceeded normally.

Animals↗
PubMed1978

Embryonic development of the pineal gland of the chicken (Gallus gallus).

A study of the embryonic development of the pineal gland of the chicken was performed with the optical microscope. The time of apparition of the first outline, as a derivative of the roof of the third ventricle, was fixed at 3 days. The major portion of the pineal parenchyma is derived from the frontal wall of the outline. All the vesicles and follicles were formed by solid mammilliform projections which subsequently presented a central lumen. In no case was a communication of the follicular cavities with the pineal recess observed. Three categories of vesicles or follicles can be distinguished according to their origin.

Animals↗