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PubMed1982

Microscopic studies on chick thrombocytes in early development.

Thrombocytes of early chick embryos were observed in blood smear and whole embryo preparations stained with PAS. In the blood smear preparations, thrombocytes usually had one large glycogen mass in the cytoplasm until 3 days of incubation, and it became progressively smaller with the advance of embryonal development. While, the application of PAS to whole embryo preparations was shown to be a very useful method for observation of the blood cells in embryos at early stages when their blood could not be collected. Thrombocytes were clearly identified in situ in the embryo by PAS staining even in very early stages when no blood circulation occurred. At stage 12, distribution of the thrombocytes coincided with that of blood islands, but was limited within the area opaca. Mitotic figures of the thrombocytes were frequently found in and near the blood islands. This suggests that blood islands are the proliferation sites of the thrombocytes in early chick embryos.

Animals↗

PubMed1975

Microtubule protein pools in early development.

Microtubule protein pools have been demonstrated to exist in unfertilized eggs and the early embryonic stages of several organisms. The microtubule pool of the sea urchin embryo is constant in size (about 0.4% of the total embryo protein) throughout early development. Protein withdrawn from this pool for organelle assembly is replaced by new synthesis. Eggs and embryos of Drosophila similarly contain a pool of microtubule proteins (larger than or equal to 0.4% of the total embryo protein, congruent to 3% of the soluble protein), which is constant in size throughout early development. The Drosophila egg microtubule proteins are easily purified by self-assembly in vitro of microtubules, and are similar to microtubule proteins from other organisms in molecular weight and other properties. Synthesis of microtubule proteins in sea urchin embryos is supported by oogenetic mRNA. This appears also to be the case in molluscan (Ilyanassa) embryos. It is not known whether Drosophila embryos synthesize microtubule proteins during the early stages of development.

Animals↗

PubMed1990

Identification of early developing axon projections from spinal interneurons in the chick embryo with a neuron specific beta-tubulin antibody: evidence for a new 'pioneer' pathway in the spinal cord.

The early development of interneurons in the chick embryo spinal cord was studied using a monoclonal antibody against a neuron-specific beta-tubulin isoform. Early developing interneurons were divided into two cell groups on the basis of their location and the pattern of growth of their axons. One group is composed of cells that establish a primitive longitudinal pathway (PL-cells), whereas the other group contains cells constituting a circumferential pathway (C-cells). The onset of axonal development in both cell groups occurs at stage (st.) 15 (embryonic day, (E), 2) in the branchial segments, which is prior to axonogenesis of motoneurons. PL-cells develop in the region between the floor plate and the motoneuron nucleus. Their axons are the first neuronal processes ('pioneer axons') to arrive in the ventrolateral marginal zone and they project both rostrally and caudally to establish a primitive longitudinal association pathway at the ventrolateral surface of the neural tube. This pathway is formed before axons of C-cells arrive in the ventrolateral region. The first C-cells are initially located in the most dorsal portion of the neural tube, whereas later appearing C-cells are also located in both intermediate and ventral regions of the neural tube. The axons of C-cells project ventrally, without fasciculating, along the lateral border of the neural tube. Some of their axons enter the ipsilateral ventrolateral longitudinal pathway at st. 17. We often observed apparent contacts and interactions between preexisting axons of PL-cells and newly arriving axons of C-cells. The axons of commissural C-cells first enter the floor plate at st. 17 and cross the midline at st. 18. Axons of C cells begin to join the contralateral ventrolateral longitudinal pathway at st. 18+ to st. 19. In the floor plate region, contacts between growth cones and axons were often observed. However, axons in the floor plate at these stages were not fasciculated. These observations establish the timing and pattern of growth of axons from two specific populations of early developing interneurons in the chick spinal cord. Additionally, we have identified an early and apparently previously undescribed 'pioneer' pathway that constitutes the first longitudinal pathway in the chick spinal cord.

Animals↗

PubMed1990

Maternal mRNA expression in early development: regulation at the 3' end.

Early development in many animals is programmed by maternal mRNAs inherited by the fertilized egg. Many of these RNAs are translationally dormant in immature oocytes, but are recruited onto polysomes during meiotic maturation or fertilization. Polyadenylation plays a major role in controlling the translation of maternal mRNA during these times of development. Polyadenylation, in turn, is dependent upon two cis elements that reside in the 3'-terminal region of responsive mRNAs. In two cases, the factors that interact with these regions have been examined. The half-life of maternal mRNA also is regulated by polyadenylation, which again is controlled by 3'-terminal cis elements. The recent literature covering these topics is reviewed.

Animals↗

PubMed1980

The early development of the nervous system in staged insectivore and primate embryos.

The early development of the nervous system was studied in stage embryos of hemicentetes semispinosus, Microcebus murinus, Alouatta seniculus, Cebus appella, Cebus albifrons, macaca mulatta, and Homo sapiens. The specimens were assigned to Carnegie stages 11-13. Serial transverse sections were examined and graphic reconstructions were prepared. The early development of the neural tube is basically similar in all the species investigated but differences in detail are noticeable. The mesencephalic flexure serves in all cases as a landmark for malpighi's tripartite subdivision of the brain. The nonhuman embryos seem to show a little more variation than the human in the closure of the neuropores in relation to somitic count. With the exception of the later-appearing terminal-vomeronasal component, all major portions of the neural crest as classified by O'Rahilly ('65) are represented in both the nonhuman and the human embryos studied. No crest is present at the level of rhombomere 1, nor at rhombomere 3 except in the platyrrhines and some human embryos, nor at rhombomere 5 except in certain human specimens. An indication of the division of the trigeminal ganglion into its primary divisions is rare at stage 11 (C. apella), may be visible at stage 12 (Alouatta, macaca, Homo), and is definite (in Homo) at stage 13. Ganglionic contributions from head ectoderm (epipharyngeal placodes), as previously described in the human and some other vertebrate embryos, were sought and found in Cebus apella. In both nonhuman and human, a tendency is noted whereby the rostral limit of the occipitospinal crest, high at stage 11, seems to descend relatively at stage 12, and ascend again at stage 13 (at least in the human) to become associated with the appearance of the accessory and hypoglossal nerves. In general, the motor components of the nerves are identifiable before the sensory elements, and, in the present study, nerve fibers were first observed in the human at stage 13 in some of the cranial nerves and in the ventral roots of the spinal nerves.

Animals↗

PubMed2000

Molecular characterization of the expression of distinct classes of cyclins during the early development of tomato fruit.

Early fruit development in tomato (Lycopersicon esculentum Mill.) proceeds from two distinct phases of growth, essentially cell division and cell expansion. In this study, we investigated the expression characteristics of the key cell-cycle regulators, mitotic and G1 cyclins, during tomato fruit development. We isolated six genes designated Lyces;CycA1;1, Lyces;CycA2;1, Lyces; CycA3;1, Lyces;CycB1:1 and Lyces;CycB2;1 encoding tomato mitotic cyclins, and Lyces;CycD3;1 encoding a G1 cyclin. The accumulation of transcripts was predominantly associated with mitotically active organs: developing fruits, young leaves and roots, and with cell-suspension cultures under appropriate sugar feeding conditions. Transcripts for all the isolated cyclin genes could be detected in the epidermis and pericarp of fruit tissues where some slight mitotic activity still remained at the onset of ripening. However, Lyces;CycA3;1 and Lyces;CycD3;1 were expressed in the gel tissue at the late stage of fruit development, suggesting that they are involved in endoreduplication of the differentiated and giant cells of the gel tissue.

Amino Acid Sequence↗

PubMed2002

Twins early development study (TEDS): a multivariate, longitudinal genetic investigation of language, cognition and behavior problems in childhood.

The Twins Early Development Study (TEDS) focuses on the early development of the three most common psychological problems in childhood: communication disorders, mild mental impairment and behavior problems. The TEDS twins were assessed longitudinally at 2, 3, 4 and 7 years of age in order to investigate genetic and environmental contributions to change and continuity in language and cognitive development; it is multivariate in order to examine the origins of comorbidity; and it uses a large sample in order to study abnormal development in the context of normal development. The twins were identified from birth records of twins born in the UK in 1994-96. More than 15,000 pairs of twins have been enrolled in TEDS and the participating families are representative of the UK. The measures at 2, 3 and 4 years are administered by parents. At 7 years, children are assessed for language and cognitive development using telephone testing, parents and children are interviewed about behavior problems, and teachers also assess behavior problems as well as academic achievement. One set of findings is that the same genes largely contribute to both language and cognitive problems and the same genes affect normal and abnormal development, a result that suggests that general impairment may be a better target for genetic research than specific language impairment independent of nonverbal cognitive problems. DNA has been obtained so far for more than 4000 pairs and is being used initially in molecular genetic studies of language problems and hyperactivity.

Birth Certificates↗

PubMed1983

NAD turnover during early development of Xenopus laevis.

The NAD pools of Xenopus laevis oocytes and early embryos can be radioactively labelled by microinjection of [adenine-3H]NAD. This technique is used to study the metabolism of NAD in oocytes and during early development. The rate at which NAD is degraded in vivo has been monitored by determining the rate of transfer of adenine residues from the NAD pool into other nucleotides and polynucleotides. In oocytes, NAD turnover is extremely slow, with a half-life of about 400 h. NAD turnover increases dramatically after fertilisation, and the half-life of the compound decreases to 37 h in 5-h-old embryos and to 10 h in 40-h-old embryos. 2 mM 3-aminobenzamide, a specific inhibitor of poly(ADP-ribose) polymerase, reduces the NAD turnover rate by about 20%, whereas 5 mM isonicotinic acid hydrazide, a specific inhibitor of NAD glycohydrolase, produces no significant inhibition. This indicates that a significant fraction of the considerable NAD turnover observed involves poly(ADP-ribose) polymerase. Our results indicate that poly(ADP-ribose) polymerase is active during early development and suggest that this activity may be involved in one or more aspects of the nuclear metabolism of the embryo.

Animals↗

PubMed1999

Molecular and biochemical characterization of the involvement of cyclin-dependent kinase A during the early development of tomato fruit.

Following fruit set, the early development of tomato (Lycopersicon esculentum Mill.) fruit comprises two distinct phases: a cell division phase and a consecutive phase of cell expansion until the onset of ripening. In this study, we analyzed cytological and molecular changes characterizing these early phases of tomato fruit development. First we investigated the spatial and temporal regulation of the mitotic activity during fruit development. The DNA content of isolated nuclei from the different fruit tissues was determined by flow cytometry analysis. The results confirm the data of mitotic activity measurements and show that cell differentiation, leading to expanded cells, is characterized by endoreduplication. Second, we isolated two cDNAs, named Lyces;CDKA1 (accession no. Y17225) and Lyces;CDKA2 (accession no. Y17226), encoding tomato homologs of the cyclin-dependent kinase (CDK) p34(cdc2). Tomato CDKA gene expression was followed at both the transcriptional and translational levels during fruit development. The transcripts for Lyces;CDKA1 and Lyces;CDKA2 and the corresponding CDKA proteins are predominantly accumulated during the phase of cell division between anthesis and 5 d post anthesis (DPA). In whole fruits, the maximum CDK activity was obtained between 5 and 10 DPA. The determination of the kinase activity using protein extracts from the different fruit tissues was in agreement with mitotic activity analysis. It showed the particular disappearance of the activity in the gel tissue as early as 15 DPA. The overall data of CDK activity measurements suggest a strong post-translational regulation of CDK at the temporal and spatial levels during early tomato fruit development.

Amino Acid Sequence↗

PubMed1997

Oocyte influences on early development: the regulatory proteins leptin and STAT3 are polarized in mouse and human oocytes and differentially distributed within the cells of the preimplantation stage embryo.

Unique protein domains, concentration gradients, and asymmetric protein distributions or polarities are principle forces establishing the identity and fate of individual cells during early development in lower vertebrates and invertebrates. Here, we present evidence that these same forces exist during mammalian development in the form of two representative regulatory proteins, leptin and STAT3. Leptin, the 16 kDa cytokine product of the obese gene (ob) is involved in the activation of STAT3, a member of the signal transducer and activation of transcription family of proteins. We examined the temporal and spatial aspects of leptin and STAT3 immunofluorescence in mouse and human oocytes and preimplantation stage embryos. The findings demonstrate that both leptin and STAT3 are polarized in the oocyte and, as a consequence of their location and the position of the cleavage planes with respect to these protein domains: (i) differences in allocation of these proteins between blastomeres occur at the first cell division such that by the 8-cell stage; (ii) unique cellular domains consisting of leptin/STAT3 rich and leptin/STAT3 poor populations of cells are generated. By the morula stage, a cell-borne concentration gradient of these proteins extending along the surface of the embryo is observed. A potential role of these proteins in early development is indicated at the morula stage where the 'inner' cells consist of blastomeres that contain little, if any, leptin/STAT3 while 'outer' cells contain both leptin/STAT3 rich and poor cells. This pattern persists through the hatched blastocyst stage with little, if any, leptin/STAT3 detected in the inner cell mass and populations of leptin/STAT3 rich and poor cells forming the trophoblast. We have examined oocytes from mutant C57BL/6J ob/ob mice which are both obese and infertile (although fertility can be restored by the exogenous provision of leptin) and have found STAT3 and the mutant (truncated) leptin protein to be present and polarized, suggesting the possibility that the truncated leptin protein may still contain operational domains which are functional during oocyte development and early embryogenesis. Furthermore, analysis of leptin and STAT3 in intact ovarian follicles suggests that these proteins may be maternally derived and in particular, that a subpopulation of follicle cells may be partly responsible for the establishment of their polarized distribution in the oocyte. The results are discussed with respect to the proposition that leptin and STAT3 have critical roles in early mammalian development, and may be involved in the determination of the animal pole of the oocyte and in the establishment of the inner cell mass and trophoblast in the preimplantation stage embryo.

Animals↗

PubMed1998

Using EC and ES cell culture to study early development: recent observations on Indian hedgehog and Bmps.

Despite great technological advances in the study of mammalian development in the past two decades, certain problems in early development, such as how the extraembryonic lineages are established, have remained intractable. We suggest that teratocarcinoma (EC) and embryonic stem cells (ES) remain useful in vitro tools for studying some of these problems. We present a continuation of our studies on the role of IHH-based signaling in early development and demonstrate that the IHH N-peptide is expressed in the outer visceral endoderm cells of both the EC and ES-derived embryoid body. We also show that Bmp2 is upregulated and Bmp4 downregulated during the differentiation of F9 EC cells into embryoid bodies, whereas both genes are upregulated when J7 ES cells differentiate into embryoid bodies. We also examine the spatial localization of Ihh, Bmp2, and Bmp4 in day 6.5-7.0 and 7.5-8.0 embryos by in situ hybridization analysis. These data support the EC temporal expression data in that all 3 genes are expressed in visceral endoderm. Bmp4 expression appears to be limited to extraembryonic regions, where mesoderm as well as visceral endoderm are stained. Ihh and Bmp2 are expressed in extraembryonic tissues and the embryo proper. Functional roles for the observed expression patterns are discussed.

Animals↗

PubMed2000

Chronic marginal iron intakes during early development in mice result in persistent changes in dopamine metabolism and myelin composition.

Marginal iron (Fe) deficiency is prevalent in children worldwide, yet the behavioral and biochemical effects of chronic marginal Fe intakes during early development are not well characterized. Using a murine model, previous work in our laboratory demonstrated persistent behavioral disturbances as a consequence of marginal Fe intakes during early development. In the present study, Swiss-Webster mice fed a control Fe diet (75 microgram Fe/g diet, n = 13 litters) or marginal Fe diet (14 microgram Fe/g diet, n = 16 litters) during gestation and through postnatal day (PND) 75 were killed on PND 75 for assessment of tissue mineral concentrations, dopamine metabolism, myelin fatty acid composition, and c- and m-aconitase activities. In addition, these outcomes were assessed in a group of offspring (n = 13 litters) fed a marginal Fe diet during gestation and lactation and then fed a control diet from PND 21-75. Marginal Fe mice demonstrated significant differences in brain iron concentrations, dopamine metabolism and myelin fatty acid composition relative to control mice; however, no difference in c- or m-aconitase activity was demonstrated in the brain. The postnatal consumption of Fe-adequate diets among marginal Fe offspring did not fully reverse all of the observed biochemical disturbances. This study demonstrates that chronic marginal Fe intakes during early development can result in significant changes in brain biochemistry. The persistence of some of these biochemical changes after postnatal Fe supplementation suggests that they are an irreversible consequence of developmental Fe restriction.

Aconitate Hydratase↗

PubMed2000

Early development of the secretory cavity of peltate glands in Humulus lupulus L. (Cannabaceae).

Early development of the secretory cavity of chemically fixed peltate glands in Humulus lupulus L. showed secretions with different densities, light, gray and dark, in the cytoplasm of disc cells and in the periplasmic space adjacent to the developing secretory cavity. Secretions were detected in the disc cell wall and subsequently in the developing secretory cavity under the subcuticular wall of the sheath. Light and gray secretions in the cavity possessed a membrane-like surface feature. Secretions were in contact with the irregular inner surface of the cuticle. Secretions contributed to the thickening of the cuticle, whereas the membrane-like surface feature contributed to a network of Cannabis striae distributed throughout the cuticle. This study supports an early development and organization of the secretory cavity in H. lupulus, parallel to those in Cannabis, and may represent common features for lipophilic glands in angiosperms.

Cannabis↗

PubMed1981

Cellular titers and subcellular distributions of abundant polyadenylate-containing ribonucleic acid species during early development in the frog Xenopus laevis.

The distribution of cytoplasmic messenger ribonucleic acids (RNAs) in translationally active polysomes and inactive ribonucleoprotein particles changes during early development. Cellular levels and subcellular distributions have been determined for most messenger RNAs, but little is known about how individual sequences change. In this study, we used hybridization techniques with cloned sequences to measure the titers of 23 mitochondrial and non-mitochondrial polyadenylate-containing [poly(A)+]RNA species during early development in the frog Xenopus laevis. These RNA species were some of the most abundant cellular poly(A)+ RNA species in early embryos. The concentrations of most of the non-mitochondrial (cytoplasmic) RNAs remained constant in embryos during the first 10 h of development, although the concentrations of a few species increased. During neurulation, we detected several new poly(A)+ RNA sequences in polysomes, and with one possible exception the accumulation of these sequences was largely the result of new synthesis or de novo polyadenylation and not due to the recruitment of nonpolysomal (free ribonucleoprotein) poly(A)+ RNA. We measured the subcellular distributions of these RNA species in polysomes and free ribonucleoproteins during early development. In gastrulae, non-mitochondrial RNAs were distributed differentially between the two cell fractions; some RNA species were represented more in free ribonucleoproteins, and others were represented less. By the neurula stage this differential distribution in polysomes and free ribonucleoproteins was less pronounced, and we found species almost entirely in polysomes. Some poly(A)+ RNA species transcribed from the mitochondrial genome were localized within the mitochondria and were mapped to discrete fragments of the mitochondrial genome. Much of this poly(A)+ RNA was transcribed from the ribosomal locus. Nonribosomal mitochondrial poly(A)+ RNA species became enriched in polysome-like structures after fertilization, with time courses similar to the time course of mobilization of cytoplasmic poly(A)+ RNA.

Animals↗

PubMed2004

Effects of methoxychlor, dieldrin and lindane on sea urchin fertilization and early development.

We have studied the effects of methoxychlor (MXC), dieldrin, and lindane on fertilization and early development of sea urchin egg. These organochlorine pesticides have often been found in polluted ground and water near agricultural sites, and have therefore been detected from time to time in the food chain and in drinking water. They have been reported to alter various reproduction functions in various animals including marine populations. We observed that the rate of fertilization decreased when the sperm was incubated with dieldrin or lindane. Treatment of eggs with each pesticide did not prevent fertilization, but increased the rate in polyspermy, delayed or blocked the first mitotic divisions, and altered early embryonic development. Moreover, all pesticides could alter several intracellular biochemical pathways that control first mitotic divisions and early development, including intracellular calcium homeostasis, MPF (mitosis promoting factor) activity and formation of the bipolar mitotic spindle. We found that lindane was the most potent of the three pesticides to alter all biochemical events. All these effects were observed at relatively high concentrations. However, bio-accumulation in sediments and aquatic organisms have been reported. Sea urchin eggs may then be in contact with very high concentrations of these pesticides in areas where these pesticides are not handled or stocked properly, and then develop into abnormal embryos.

Animals↗

PubMed1997

Effects of cyclin A2 noncoding regions on reporter gene translation during early development of Xenopus laevis.

The repression of translation of Xenopus cyclin A2 transcripts during early development was examined by analyzing the effects of cyclin A2 noncoding regions using a CAT reporter system. On their own, the 5' and 3' UTRs (untranslated regions) were unable to inhibit reporter translation until approximately the time of the midblastula transition. Transcripts containing the 3' UTR were polyadenylated after fertilization and the midblastula transition. When both noncoding regions flanked a CAT reporter gene, translation was repressed at all stages of development examined in spite of their polyadenylation after fertilization. From these data, we conclude that the 5' and 3' UTRs interact synergically to prevent translation during early development and that the poly(A) tail is insufficient to promote their translation.

Animals↗

PubMed2000

Early development of human gastric H,K-adenosine triphosphatase.

BACKGROUND: Little is known about the early development of the gastric acid secretion in human neonates. The purpose of this study was to examine the early development of gastric H,K-adenosine triphosphatase (ATPase) by analyzing human gastric biopsy specimens. METHODS: Eighty-eight neonates from week 25 to week 42 of gestation who were treated in a neonatal intensive care unit underwent gastroscopy with biopsy specimens obtained from the corpus. The expression of gastric H,K-ATPase protein in the gastric biopsy specimens was assessed by Western blot analysis, using an antibody directed against the gastric H,K-ATPase. The amount of H,K-ATPase expressed was compared with age, gender, clinical factors, diseases, and the macroscopic and histologic findings at endoscopy. RESULTS: The expression of human gastric H,K-ATPase increased significantly with gestational age. There was a significant increase in the expression of gastric H,K-ATPase during the first 82 days after birth. Boys had a significantly higher expression of gastric H,K-ATPase than girls did, when it was adjusted for gestational and postnatal age. Neither the clinical features nor treatments showed significant correlations with the expression of human gastric H,K-ATPase when controlling for gestational and postnatal age. CONCLUSIONS: This study shows that human gastric H,K-ATPase is expressed from week 25 of gestation, which agrees with earlier findings of gastric pH in preterm infants. The amount of enzyme expressed increases with gestational and postnatal age. The authors speculate that the susceptibility to gastric lesions seen in neonates is not related to the amount of H,K-ATPase. However, studies elucidating the ontogeny of gastric mucosal defense mechanisms are warranted.

Biopsy↗

PubMed1995

Cloning of a Xenopus laevis cDNA encoding focal adhesion kinase (FAK) and expression during early development.

Focal adhesion kinase (FAK) is a widely produced nonreceptor protein-tyrosine kinase thought to participate in signalling pathways activated in response to cell interaction with the extracellular matrix. Fibronectin-dependent cell adhesion mediated by integrin receptors plays a critical role in mesodermal cell migration during amphibian gastrulation in early development. As a first step toward understanding the role of FAK in Xenopus laevis (Xl) early development, we isolated cDNAs encoding Xl FAK and deduced the entire amino acid (aa) sequence. Xl FAK has 89-91% overall identity to the homologs previously described from mouse, human and chicken sources. Within the catalytic domain, the aa identity is about 97%. Northern blot analysis revealed that abundant maternal FAK transcript is present in Xl eggs, with levels decreasing slightly through cleavage and early blastula stages. At early gastrulation, the FAK mRNA level becomes modestly elevated, followed by a steady decline through late gastrulation. The mRNA level undergoes a further drop at the neurula stage, then begins a steady increase through the tailbud and tadpole stages. These data indicate that the steady-state level of FAK mRNA is regulated during Xl early development, and are consistent with a proposed role for FAK in the process of gastrulation.

Amino Acid Sequence↗