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PubMed1993

Gamma-tubulin reorganization during mouse fertilization and early development.

gamma-Tubulin, a component of spindle pole bodies in fungal cells and pericentriolar material in vertebrate cells, is thought to play a role in the nucleation of microtubule growth and to define their polarity. In contrast to the adult somatic cells, microtubules are nucleated in the absence of centrioles in mammalian oocytes and early embryos. By studying acentriolar mouse oocytes and their early development following fertilization, we show that gamma-tubulin antibody crossreacts with a 50,000 M(r) protein in unfertilized mouse oocytes and demonstrate that gamma-tubulin distribution is rearranged dramatically during fertilization. In unfertilized mouse oocytes, gamma-tubulin is concentrated in the broad spindle poles of meiotic spindle (MII) and as the distinct foci which form the centers of the cytoplasmic microtubule asters (cytasters). The integrity of these gamma-tubulin foci and their cytoplasmic location is maintained during the drug- or cold-induced depolymerization of microtubules. gamma-Tubulin is also found in the basal body of the mouse sperm. During fertilization, the gamma-tubulin is found at the cytastral centers as well as in the incorporated sperm basal body complex, and the gamma-tubulin foci coalesce at the perinuclear microtubule organizing regions of the two pronuclei at the first mitotic prophase. During mitosis, gamma-tubulin is found associated with broad bands that form the poles of the first mitotic spindle. By the late preimplantation stage, when newly generated centrioles have been reported to arise, gamma-tubulin remains localized at the centrosome of mitotic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Understanding hypoxia-induced gene expression in early development: in vitro and in vivo analysis of hypoxia-inducible factor 1-regulated zebra fish insulin-like growth factor binding protein 1 gene expression.

Insulin-like growth factor binding protein 1 (IGFBP-1) is a hypoxia-inducible gene that plays an important role in regulating embryonic growth and development under hypoxic stress. The molecular mechanisms underlying hypoxia-induced IGFBP-1 gene expression in the embryonic tissues are not well understood. Here we report that the hypoxia-inducible factor 1 (HIF-1) pathway is established in early embryogenesis and mediates hypoxia-induced IGFBP-1 expression. Hypoxia increased the HIF-1 activity, and HIF-1alpha overexpression or CoCl2 treatment resulted in elevated IGFBP-1 expression in zebra fish embryos. Although the zebra fish IGFBP-1 promoter contains 13 consensus hypoxia response elements (HREs), deletion and mutational analysis revealed that only the HRE positioned at -1090/-1086 is required for the hypoxia and HIF-1 induction. Further experiments revealed that there is an HIF-1 ancillary sequence (HAS) adjacent only to the functional HRE. Mutation of this HAS greatly reduced the responsiveness of the IGFBP-1 promoter to hypoxia and HIF-1. The HAS does not directly bind to HIF-1 or affect the binding of the HRE to HIF-1. The HAS is bound to a nuclear protein(s), and this HAS binding activity is reduced by hypoxia. These results suggest that HIF-1 mediates hypoxia-induced IGFBP-1 gene expression in early development by selectively interacting with the -1090/-1086 HRE and its adjacent HAS.

Animals↗

PubMed2002

dELL, a drosophila homologue of transcription elongation factor ELL (Eleven-nineteen Lysine rich Leukemia), is required for early development.

ELL (Eleven-nineteen Lysine rich Leukemia) is known to be an elongation factor resembling elongin for RNA polymerase II transcription. A homologue of human ELL (hELL) was identified in Drosophila melanogaster (dELL) and several cDNA clones were isolated from the embryonic cDNA library. We showed that dELL is expressed mainly in the ovaries and early embryonic stages by developmental Northern blot. dELL encodes a protein of 912 amino acids which is substantially longer than the hELL (612 aa). Immunostaining revealed that dELL was localized to nuclei in early embryos and to nuclei of nurse cells and follicle cells in the ovary suggesting its important role in early development of drosophila. To elucidate the function of this gene in drosophila, P-element mobilization was performed by utilizing a P-element inserted upstream of dELL. Southern analysis showed that isolated mutants are internal P-element deletions. These P-element deletions can now be used to isolate dELL mutations by EMS mutagenesis.

Amino Acid Sequence↗

PubMed1987

Early development of photoreceptors in the ventral retina of the zebrafish embryo.

The first photoreceptor outer segments in the retina of the zebrafish Brachydanio rerio appear in the embryo 2.5 days after fertilization, as revealed by scanning and transmission electron microscopy. These outer segments arise in a small region ventral to the exit of the optic nerve. Ultrastructural features of the developing photoreceptor cells, especially those that distinguish the rods and cones, are described. By 3 days after fertilization, the time of hatching, photoreceptor outer segments are widespread in the retina. However, at this time and in the young larva the early developing ventral region remains distinctive because of its conspicuous population of rods.

Animals↗

PubMed1993

[Studies on the early development of nucleocytoplasmic hybrid embryos between mouse and rabbit by nuclear transplantation].

Nuclear transplantation has been proved to be a very powerful method in researching the relationship between nucleus and cytoplasm during embryogenesis. Electrofusion is a new means of cell fusion which is being improved in the past nearly ten years. In this study, we produced interorder nucleocytoplasmic hybrid embryos between mouse and rabbit with these two techniques. Two phenomena, i.e. premature chromosome condensation (PCC) and nuclear swelling, were observed after mouse 8-cell stage blastomeres were fused into rabbit enucleated oocytes. After 4.5-days cultured in mouse oviducts, 5.4% reconstituted embryos developed into blastocysts. By karyotype examination, it was known that only mouse chromosomes were presented in the blastomeres, one blastocyst even had a normal mouse karyotype (2 n = 40, XX). As a conclusion, we consider it is possible to obtain normal early development of interspecies nucleocytoplasmic hybrid embryos between mouse and rabbit.

Animals↗

PubMed1988

Kinetics of histone gene expression during early development of Xenopus laevis.

Using literature data for transcriptional and translational rate constants, gene copy numbers, DNA concentrations, and stability constants, we have calculated the expected concentrations of histones and histone mRNA during embryogenesis of Xenopus laevis. The results led us to conclude that: (i) for X. laevis the gene copy number of the histone genes is too low to ensure the synthesis of sufficient histones during very early development, inheritance from the oocyte of either histone protein or histone mRNA (but not necessarily both) is necessary; (ii) from the known storage of histones in the oocyte and the rates of histone synthesis determined by Adamson & Woodland (1977), there would be sufficient histones to structure the newly synthesized DNA up to gastrulation but not thereafter (these empirical rates of histone synthesis may be underestimates); (iii) on the other hand, the amount of H3 mRNA recently observed during early embryogenesis (Koster, 1987, Koster et al., 1988) could direct a higher and sufficient synthesis of H3 protein, also after gastrulation. We present a quantitative model that accounts both for the observed H3 mRNA concentration as a function of time during embryogenesis and for the synthesis of sufficient histones to structure the DNA throughout early embryogenesis. The model suggests that X. laevis exhibits a major (i.e. some 14-fold) reduction in transcription of histone genes approximately 11 hours after fertilization. This reduction could be due to a decrease in the number of transcribed histone genes, a decreased rate constant of transcription with continued transcription of all the histone genes, and/or a reduction in the time during the cell cycle in which histone mRNA synthesis takes place. Alternatively, the histone mRNA stability might decrease approximately 16-fold 11 hours after fertilization.

Animals↗

PubMed2004

Diets containing soy protein isolate increase hepatic CYP3A expression and inducibility in weanling male rats exposed during early development.

Hepatic CYP3A enzymes were studied in weanling male Sprague-Dawley rats exposed to diets from gestational d 4 in which the sole protein source was either casein (CAS) or soy protein isolate (SPI). At age 25 d, rats were gavaged with corn oil or one of the CYP3A inducers, dexamethasone (DEX) and clotrimazole (CLT), at a dose of 50 mg/kg. Little CYP3A1 (CYP3A23), CYP3A2, or CYP3A9 mRNA was observed in CAS-fed weanling rats but CYP3A18 mRNA was readily detectable in Northern blots. In contrast, consumption of SPI without inducer treatment resulted in the expression of CYP3A1 (CYP3A23), and CYP3A2 mRNAs, expression of CYP3A apoprotein in hepatic microsomes, and a 2-fold greater turnover of the CYP3A substrate midazolam (P < 0.05). DEX induced CYP3A1, CYP3A2, and CYP3A9 (P < 0.05), but not CYP3A18 mRNA expression in rats fed both diets. Hepatic CYP3A apoprotein expression and midazolam 4-hydroxylation in SPI-fed rats was greater than that of CAS-fed rats after DEX treatment (P < 0.05). CLT also induced CYP3A2 mRNA 2-fold in rats fed both diets but CYP3A apoprotein expression in microsomes from SPI-fed CLT rats was double that of CLT-treated rats fed CAS (P < 0.05). The elevation of CYP3A apoprotein due to SPI and the CYP3A apoprotein induction by DEX and CLT treatment yielded no significant diet x inducer interaction. Analysis of heterologous nuclear RNA expression by RT-PCR using intron-specific primers for CYP3A1 revealed a 14-fold increase in RNA transcription in CAS-fed rats after treatment with DEX (P < 0.05) but no increase in rats fed SPI compared with rats fed CAS even though CYP3A1 mRNA and CYP3A apoprotein were significantly elevated. These data demonstrate that exposure to SPI during early development can increase CYP3A expression via post-transcriptional mechanisms and suggest that early soy consumption has potential effects on the metabolism of a wide variety of CYP3A substrates.

Animals↗

PubMed1999

Germ cell migration and early development of the gonads in the trisomy 16 mouse--an animal model for Down's syndrome.

The aneuploid condition of patients with Down's syndrome (trisomy 21) frequently leads to a sub- or infertility of these individuals. Gonads from adults and fetuses with trisomy 21 demonstrated histologically a remarkable reduction in germ cells. Disorders in the germ cell migration, the early development of the gonads as well as meiotic defects are thought to contribute to this pathomorphology. To gain information about premeiotic defects, investigations on the trisomy 16 mouse, an animal model for Down's syndrome, were carried out. By means of morphometric studies a delay in migration and a reduction in primordial germ cells was evaluated in trisomic mice of embryonic day 11 (E11). At day E13 a generalized growth retardation of the developing gonads was obvious in trisomic animals. Additionally performed electron microscopic examinations revealed signs of germ cell demise in trisomy 16 mice. Thus, the mechanisms of a diminished proliferation capacity, impaired migration and premature death of germ cells represent premeiotic disorders that presumably contribute to the pathomorphology observed in the gonads of individuals with Down's syndrome.

Alkaline Phosphatase↗

PubMed1992

Transcriptional regulation by folate: inducible gene expression in Dictyostelium transformants during growth and early development.

The Dictyostelium discoidin genes are induced in bacteria-grown cells shortly before the onset of development but are also highly expressed during growth in axenic medium. We here show that axenically growing cells strongly respond to the extracellular signal folate by suppressing discoidin synthesis while cell growth and development is not substantially affected. Repression occurs via two previously identified promoter elements, the dIE and the dAXE. Removal of the signal molecules or setting cells up for development results in rapid reactivation of the promoter. Based on this observation, we constructed the transformation vector pVEII and describe a convenient method which allows for controlled expression of a gene of interest in growing cells and also for external modulation in early development. Deletion constructs of the discoidin promoter can be used in addition to vary transcriptional activity over about one order of magnitude.

Animals↗

PubMed1976

Effect of 5-fluorouracil and cycloheximide on the early development of Phycomyces blakesleeanus spores and the activity of N-acetylglucosamine synthesizing enzymes.

The development of germinating Phycomyces spores was not inhibited by 5-fluorouracil (1mM) until the emergence of the germination tube. Fluorouracil was incorporated into RNA as efficiently as uracil; it did not inhibit the synthesis of proteins and the increase in respiratory activity during early development. Cycloheximide inhibited development as well as the increase in respiration and protein synthesis. This suggested that protein synthesis or some other cycloheximide dependent process, but no mRNA synthesis, was needed for the first developmental stages. The activity of two enzymes involved in the synthesis of N-acetylglucosamine increased markedly during germination. THis increase was inhibited by both 5-fluorouracil and cycloheximide; this suggested that those enzymes were synthesized on mRNA formed during germination.

Acetylglucosamine↗

PubMedDate not supplied

Membrane digestion and nutrient assimilation in early development.

Advances in the study of membrane digestion are described which relate to techniques for the separation of the apical glycocalyx and the study of the distribution of enzymes between the latter and the cell membrane. The regulatory properties of brush border enzymes have been demonstrated. Membrane digestion by pancreatic enzymes adsorbed on the mucosal surface and by enteric enzymes predominates in early development, whereas intraluminal digestion develops during the transition to definitive (adult) nutrition. Substrate and other, non-substrate factors are involved in the regulation of intraluminal and membrane digestion in ontogeny. The importance of lipid components of the diet for the maintenance of proximal-distal gradients of enzyme activity in the small intestine during the transition from milk to adult nutrition is discussed. At this period of development hydrocortisone affects both the synthesis of enzymes and their incorporation into the enterocyte membrane. The inducibility of different enzymes is not identical. The hypothesis has been proposed that stress is one of the factors inducing or repressing the synthesis of brush border enzymes. These effects are mediated through the hypothalamus, adrenals, hypophysis and thyroid. The experimental findings demonstrate that various stressors are responsible for the induction of sucrase, maltases, gamma-amylase, peptidases and alkaline phosphatase, and for the repression of lactase in suckling rats.

Aging↗

PubMed1981

Desmosines in human urine. Amounts in early development and in Marfan's syndrome.

Desmosines from 24 h human urine samples were isolated, characterized and quantified. The desmosines are in peptidyl form (1000--1500 molecular weight), and their amount is decreased by two-thirds between 7 and 25 years of age. Patients with Marfan's syndrome have significantly lower urinary amounts of desmosines than do comparable controls during the early development period.

Adolescent↗

PubMedDate not supplied

Early development of NADPH diaphorase-expressing neurons in the brain of the urodele amphibian Pleurodeles waltl.

The distribution of nitrergic cells was studied in the brain of the urodele amphibian Pleurodeles waltl during embryonic and larval stages by means of NADPH-diaphorase histochemistry. The first positive neurons were observed at embryonic stage 30 in the ventrolateral area of the caudal rhombencephalon. Subsequently (stage 33b), weakly reactive cells appeared in the isthmic tegmentum, the mesencephalic tegmentum, the hypothalamus, and the nucleus of the solitary tract. At initial larval stages (34-38), two new groups of NADPH-diaphorase-positive cells appeared in the caudal telencephalon (the amygdaloid region) and in the middle reticular nucleus. During the beginning of the active larval life (stages 39-42), reactive cells were found in the granule cell layer of the olfactory bulb and in the telencephalic pallium. As in the adult, the nitrergic cells in the central nervous system are widely distributed during early development, pointing to important roles of nitric oxide through ontogenesis. The sequence of appearance of nitrergic cells suggests an early involvement in reticulospinal control most likely related to locomotor behavior.

Aging↗

PubMed1998

Control of gene expression in Xenopus early development.

We examine the control of gene expression before and through the MBT in Xenopus laevis. The generalized repression of transcription that occurs before the midblastula transition (MBT) is regulated by a dynamic competition between chromatin and transcription complex assembly. Conditions favoring the access of basal factors (TBP) or transactivators can overcome this transcriptional repression. Changes in DNase I hypersensitivity patterns of the chromatin during early development show that it is more accessible to DNase I before the MBT (and by extension to other DNA interacting proteins) than after the MBT. We also show that at the level of genomic domains, organization of the chromatin matrix attachment sites is random before MBT. We propose that these three components, chromatin domain structure, DNA accessibility, and the transcription complex-chromatin dynamic competition, combine to regulate transcription in the embryo before and through the MBT.

Animals↗

PubMed2005

Two formulations of the industrial surfactant, Toximul, differentially reduce mouse weight gain and hepatic glycogen in vivo during early development: effects of exposure to Influenza B Virus.

Previous studies demonstrated that young mice exposed chronically to industrial surfactant (IS) do not exhibit obvious adverse health effects, but do have persistently reduced body weights and compromised hepatic energy metabolism. The present study examined the time course of effects of two formulations of the Toximul (Tox) class of anionic/nonionic IS on body weights and liver glycogen (+/-virus) during early development. Results showed that effects differed in two commonly used strains of mice. In CFW mice, 12 days' exposure to Tox resulted in retardation of weight gain that was most obvious several days after exposure ceased. In this strain effects were greater with Tox 3409F than with Tox MP-A and appeared to be reversible except when the mice were treated with both Tox 3409F and FluB. Weights of the CD-1 mice were not affected by either Tox treatment alone, but were significantly reduced on postnatal day 20 when Tox exposure had been combined with FluB infection. Postnatal replenishment of hepatic glycogen stores during the first three weeks also occurred at different rates in CFW and CD-1 mice. The effects of Tox (+/-FluB) on glycogen also varied with mouse strain and Tox formulation. In CFW mice, exposure to either formulation resulted in significant (55-59%) reductions in glycogen, although reductions were not evident until nine days after Tox exposure stopped. By contrast, hepatic glycogen in CD-1 mice was reduced both during and after dermal exposure to Tox 3409F, whereas no effect was observed with Tox MP-A. Notably, the 3409F effect was reversible in the CD-1 mice, but reversal did not occur in mice also infected with FluB. Tox MP-A+FluB-treated mice exhibited only a transient glycogen reduction. These results illustrate the importance of mouse strain and formulation specificities in assessing biological effects of xenobiotic surfactants. As well, they emphasize that chronic IS exposure can induce changes in growth and energy substrate availability in young mice that may not be evident unless there is a precipitating cofactor such as a viral infection.

Animals↗

PubMed2005

Early development of neurophysiological processes involved in normal reading and reading disability: a magnetic source imaging study.

This longitudinal study examined the development of the brain mechanism involved in phonological decoding in beginning readers using magnetic source imaging. Kindergarten students were assigned to 2 groups: those who showed mastery of skills that are important predictors of proficient reading (low-risk group) and those who initially did not show mastery but later benefited from systematic reading instruction and developed average-range reading skills at the end of Grade 1 (high-risk responders). Spatiotemporal profiles of brain activity were obtained during performance of letter-sound and pseudoword naming tasks before and after Grade 1 instruction. With few exceptions, low-risk children showed early development of brain activation profiles that are typical of older skilled readers. Provided that temporoparietal and visual association areas were recruited into the brain mechanism that supported reading, the majority of high-risk responder children benefited from systematic reading instruction and developed adequate reading abilities.

Analysis of Variance↗

PubMed2006

Delineation of the roles played by RasG and RasC in cAMP-dependent signal transduction during the early development of Dictyostelium discoideum.

On starvation, the cellular slime mold Dictyostelium discoideum initiates a program of development leading to formation of multicellular structures. The initial cell aggregation requires chemotaxis to cyclic AMP (cAMP) and relay of the cAMP signal by the activation of adenylyl cyclase (ACA), and it has been shown previously that the Ras protein RasC is involved in both processes. Insertional inactivation of the rasG gene resulted in delayed aggregation and a partial inhibition of early gene expression, suggesting that RasG also has a role in early development. Both chemotaxis and ACA activation were reduced in the rasG- cells, but the effect on chemotaxis was more pronounced. When the responses of rasG- cells to cAMP were compared with the responses of rasC- and rasC- rasG- strains, generated in otherwise isogenic backgrounds, these studies revealed that signal transduction through RasG is more important in chemotaxis and early gene expression, but that signal transduction through RasC is more important in ACA activation. Because the loss of either of the two Ras proteins alone did not result in a total loss of signal output down either of the branches of the cAMP signal-response pathway, there appears to be some overlap of function.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed2007

Expression of enzymes involved in thyroid hormone metabolism during the early development of Xenopus tropicalis.

BACKGROUND INFORMATION: There are significant indications that amphibians require TH (thyroid hormones) prior to their involvement in the regulation of metamorphosis and before the development of a functional thyroid. RESULTS: In order to investigate the potential role for TH in pre-metamorphic Xenopus tropicalis we have cloned cDNAs for, and analysed the expression of, TPO (thyroid peroxidase), 5'DII (type II iodothyronine deiodinase) and 5DIII (type III iodothyronine deiodinase), enzymes involved in TH metabolism. Zygotic expression of TPO was detected in neurula stage embryos. Expression was observed in the notochord and later in the thyroid. The notochord was also a common site of expression for 5'DII and 5DIII. Other sites of 5'DII expression are the otic vesicles, retina, liver, blood-forming region, branchial arches and brain. 5DIII is also expressed in the brain, retina, liver, developing pro-nephros, blood-forming region and branchial arches. Embryos exposed to the TPO inhibitor methimazole showed a distinctive dose-dependent phenotype of a crimped notochord and shortened axis, together with alterations in (125)I(-) uptake. CONCLUSIONS: These data suggest a novel extrathyroidal role for TH during early development, and support the proposal that embryos require thyroid signalling for normal development prior to metamorphosis.

Animals↗