SEARCH · PubMed Health

Results for “Early development”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

PubMed1998

Selective outgrowth and differential tropism of amacrine and photoreceptor axons to cell targets during early development in vitro.

The axonal guidance and outgrowth in retinal neurons were investigated in cultures of pure retinal neurons (control) or in cocultures with heterologous BC3H-1 cells. Under control conditions, only about 10% of retinal neurons developed axons; coculturing with BC3H-1 cells induced early axonal outgrowth and guidance to BC3H-1 cells in most amacrine neurons. Both mechanisms were dependent on laminin and neural cell-adhesion molecules (N-CAMs) released by BC3H-1 cells, because they were prevented by antibodies directed against these molecules. The protein kinase C (PKC) inhibitor, staurosporine, reduced the effect of laminin on amacrine axonal outgrowth, suggesting that this effect was mediated by PKC. The occurrence of structures resembling synaptic boutons and the expression of synaptophysin at the amacrine axon ends of heterologous connections suggested that amacrine axons establish true synaptic contacts rather than simply overlapping with the BC3H-1 cells. In contrast to the heterologous contacts with BC3H-1 cells, the amacrine-amacrine axonal contacts observed in the cocultures were independent of laminin and N-CAM. Axonal outgrowth occurred in about 10% of the photoreceptors and was not affected by BC3H-1 cells or by substratum pretreatment with laminin or N-CAM. These results show that different mechanisms affect axonal outgrowth and guidance in amacrine and photoreceptor neurons in vitro, and they suggest that similar mechanisms could contribute to the development of the scaffold of axon pathways in the retina in vivo.

Animals↗

PubMed2006

[Early development and learning conditions: the role of the executive functions].

INTRODUCTION: From the neuroconstructivist approach, cognitive development is understood and studied as a process of successive rearrangement, as are its mechanisms of change and its differential results. The early years of life are essential in being able to explain the differential cognitive, emotional and social competencies. Changes in the executive functions play a crucial role in this process. Understanding it calls for interdisciplinary research that relates neuroanatomical data about the brain with functional and psychological data. AIMS: To further our knowledge in a number of different disciplines about early executive functioning in infants with differential courses of development (typical infants, infants with Down syndrome, infants born with risk factors). We suggest the existence of an early differential gradient of executive functioning. SUBJECTS AND METHODS: A comparative and longitudinal study was conducted into the activity of typical infants (n = 10), infants with a risk factor (n = 6 infants with congenital hypothyroidism; n = 6 infants born underweight) and infants with Down syndrome (n = 6), using a stimulating material, at 1.3 years and again 9 months later. Data was analysed both qualitatively and quantitatively. RESULTS: The two groups that were studied showed different patterns of early executive functioning, and the biggest difference was observed between typical infants and infants with Down syndrome. The infants with risk factors were located on a gradient between these two, although closer to the former but with certain differences. It is also noted how the executive functions develop over the ages that were studied. CONCLUSION: These differences in executive functioning provide us with guidelines on interventions aimed at harmonising early cognitive development.

Child Development↗

PubMed2006

Transcriptional control of pluripotency: decisions in early development.

The pathways controlling the maintenance and loss of pluripotency in cells of the early embryo regulate the formation of the tissues that will support development. Several transcription factors have been identified as being integral to the establishment and/or maintenance of pluripotency, coordinately regulating the expression of genes within pluripotent cells and acting as gene targets of these same processes. Recent advances in understanding the transcriptional regulation of these factors have revealed differences in the transcriptional complexes present within sub-populations of the pluripotent lineage and in the mechanisms regulating the loss of pluripotency on differentiation.

Animals↗

PubMed1974

[Nuclear function during early development of remote fish hybrids].

The participation of paternal genome was studied in the development of remote hybrids obtained as a result of artificial insemination of the loach (Misgurnus fossilis) eggs by the sperm of aquarial Cyprinids (Brachydanio rerio, Danio malabaricus, Barbus tetrazona, Razbora heteromorpha, Carassius auratus) and Cobitids (Acanthophtalmus kuhlii). The hybrids obtained differed at the stage of hatching both from each other and from the loach by some morphological features. To study the function of heterologous nuclei, haploid nucleocytoplasmic hybrids were obtained by means of chromosome inactivation in the loach eggs by heavy doses of X-rays. The participation of paternal genome in development was estimated by comparison of the curves of viability of diploid and haploid hybrids with those of diploid, haploid and "anuclear" loach embryos. Patterns of mortality of embryos and larvae in each hybrid combination (percentage, stage) suggest the functioning of paternal genome already at the early stages of development. The activity of hybrid and heterologous nuclei was also estimated by the onset and the intensity of morphogenetic function which was determined by the time of embryonic death following nuclear inactivation at different stages. The onset of nuclear function in all hybrids coinsides with that in the loach, except B. rerio in which it occurs somewhat earlier. The data obtained prove the participation of paternal genes in development and maintenance of viability of embryos at all developmental stages beginning from the early ones (blastula).

Animals↗

PubMed1999

Immunohistochemical localization of laminin, nidogen, and type IV collagen during the early development of human liver.

There is evidence that basement membrane components control differentiation of liver sinusoids and bile ducts. These processes occur in humans in the 9th gestational week (GW). Distribution of laminin, nidogen, and type IV collagen was studied during human liver development between the 6th and the 10th GW. Laminin and nidogen lined intrahepatic microvessels in the 6th and 7th GW decreasing in quantity at the beginning of the fetal period (9th-10th GW). Type IV collagen was detected in microvessels only from the 9th GW onward. In the early periportal matrix (9th-10th GW) laminin, nidogen, and type IV collagen were diffusely distributed. At these stages, basement membrane zones of larger portal vessels and of early bile ducts were also stained for all three glycoproteins. These results show that laminin and nidogen are localized in microvessels during early human liver development and decrease in concentration at the developmental stage during which microvessels become discontinuous. In contrast, type IV collagen is not present in early microvessels but occurs when laminin and nidogen disappear. The three glycoproteins occur together only in those areas of the developing liver in which, from the 9th GW onward, the differentiation of immature liver cells into biliary epithelium takes place.

Basement Membrane↗

PubMed1984

Fibronectin synthesis during oogenesis and early development of the amphibian Pleurodeles waltlii.

Fibronectin (FN) synthesis during oogenesis and early embryogenesis of the amphibian Pleurodeles waltlii was investigated. The isotopically labelled amino acids [3H]leucine and [35S]methionine were incubated with oocytes or microinjected into embryos. Newly synthesized FN was analysed by polyacrylamide gel electrophoresis, using the high resolution two-dimensional gel system described by O'Farrell. With this method and fluorography we demonstrate that FN synthesis begins during oogenesis. De novo synthesized FN appears during cleavage and gastrulation. Using actinomycin D we show the presence of maternal messenger RNA coding for FN. It is translated during the cleavage and gastrulation stages.

Animals↗

PubMed1977

Noncoincidence of histone and DNA synthesis in cleavage cycles of early development.

The times of histone and DNA synthesis do not coincide in early cleavage of the sea urchin embryo. In fact, the production of histones increases during the interval after DNA synthesis (G2). Enucleate merogones, parthenogenetically activated, synthesize histones encoded upon maternal histone messenger RNA. The pattern of protein synthesis changes following fertilization, in part, but not solely, due to the increasing synthesis of histones relative to other proteins. Regulation of histone synthesis and the loading of newly replicated DNA with histones must themselves undergo change at the time of transition from cleavage cycles to cycles more typical of somatic cells.

Animals↗

PubMed2001

The cholinergic innervation develops early and rapidly in the rat cerebral cortex: a quantitative immunocytochemical study.

A recently developed method for determining the length of cholinergic axons and number of cholinergic axon varicosities (terminals) in brain sections immunostained for choline acetyltransferase was used to estimate the areal and laminar densities of the cholinergic innervation in rat frontal (motor), parietal (somatosensory) and occipital (visual) cortex at different postnatal ages. This cortical innervation showed an early beginning, a few immunostained fibers being already present in the cortical subplate at birth. In the first two postnatal weeks, it developed rapidly along three parameters: a progressive increase in the number of varicosities per unit length of axon, and a lengthening and branching of the axons. Between postnatal days 4 and 16, the number of varicosities increased steadily from two to four per 10 microm of cholinergic axon. The mean densities of cholinergic axons increased from 1.4 to 9.6, 1.7 to 9.3 and 0.7 to 7.2 m/mm(3), and the corresponding densities of varicosities from 0.4 to 3.9, 0.4 to 3.5, and 0.2 to 2.6x10(6)/mm(3) in the frontal, parietal and occipital areas, respectively. The rate of growth was maximal during these first two weeks, after which the laminar pattern characteristic of each area appeared to be established. Adult values were almost reached by postnatal day 16 in the parietal cortex, but maturation proceeded further in the frontal and particularly in the occipital cortex. These quantitative data on the ingrowth and maturation of the cholinergic innervation in postnatal rat cerebral cortex substantiate a role for acetylcholine in the development of this brain region and emphasize the striking growth capacity of individual cholinergic neurons.

Acetylcholine↗

PubMed2000

Early development of nouns and verbs in French: exploring the interface between lexicon and grammar.

Early acquisition of nouns and verbs across languages is a key issue for a number of recent studies that question the reality of the 'noun-bias' and wonder about the reasons why it exists as they explore the role of cognitive vs. more language-specific input factors. Addressing this issue, the present study investigates how the noun and verb word classes develop in the free speech of a French child between the ages of 1;2 and 2;6, from the perspective of semantic and grammatical development. The analyses indicate that, in French acquisition, nouns clearly predominate over verbs until age 1;8 at least, but that verbs are produced in the early stages. Concrete object names among nouns and concrete action verbs among verbs were found to be the most prevalent categories, but they were not the earliest to appear and their distribution revealed an asymmetry in the conceptual packaging of nouns and verbs. Verb grammaticalization, assessed through inflection and auxiliary use, lagged somewhat behind noun grammaticalization, assessed through determiner use. This result supports the hypothesized noun-verb grammatical asynchrony. Verb grammaticalization seems to be related to the production of concrete action verbs, and noun grammaticalization to that of concrete object nouns, indicating interactions between semantic and grammatical development. These findings, discussed in a cross-linguistic perspective, suggest that both conceptual and grammatical packaging are important and interacting factors in noun and verb development, and argue in favour of a constructivist approach to language acquisition.

Child Language↗

PubMed1981

A proposed mechanism for the early development of the human tracheobronchial tree.

The development of the lung in 25 human embryos and early fetuses up to 140 mm crown-rump length was studied by examination of serial histologic sections, morphometry, and selected reconstructions. The proportion of pulmonary tissue consisting of tracheobronchial tree increases during this period. Bronchial cross-sectional diameter, length of the most distal bronchial branches, and thickness of the distal mesenchyme decline during development. The results are consistent with the concept that the dichotomous branching of the growing tracheobronchial tree occurs because of resistance to forward growth f the bronchial branch by compresses mesenchyme, pleura, or adjacent structures. Division and further growth of the bronchus takes place in areas of lower resistance. This process produces a "filling in" of space available for lung development and brings the epithelial and mesenchymal elements into their definitive relationships.

Bronchi↗

PubMed1998

Gestures and words in early development of children with Down syndrome.

This study investigated the development of language and communication in children with Down syndrome (DS). More specifically, the aim was to examine the relations among verbal comprehension, verbal production, and gesture production in the very early stages of development. Forty children (age range: 10-49 months) with DS and 40 children with normal development (age range: 8-17 months) participated in this study. Children with DS came from two Italian health centers. The communicative and linguistic development of children with DS was measured by administering the Italian version of the MacArthur Communicative Development Inventory. The children with DS were severely delayed when compared with normally developing children in reaching the developmental stages. In such children a dissociation emerged between verbal comprehension and production, in favor of comprehension, whereas a synchronous development was found between vocal lexical comprehension and gestural production. The individual differences previously reported in these children are also evident in all domains examined. There were no significant differences between children with DS and typically developing controls matched for lexical comprehension on verbal production. However the two groups differed significantly in gestural development, suggesting a "gesture advantage" in children with DS compared with controls matched for word comprehension. Some possible reasons for this dissociative profile are discussed.

Age Factors↗

PubMed1984

Glycosphingolipids of chicken skeletal muscle in early development and genetic dystrophy.

The acidic and neutral GSL of chicken pectoral muscle and the activities of relevant sialyltransferase and glycosidases have been examined during embryonic and early post-hatching development. At this stage of myogenesis, a prominent shift to the neutral GSL of longer oligosaccharide length involving Forssman glycolipid most prominently and also globoside and GbOse3Cer occurred but the distribution of muscle-type gangliosides was not obviously affected. The glycosidase and sialyltransferase activities decreased dramatically just prior to or at hatching. The fusion-linked change in GSL suggests a role for terminal galactosamine and/or galactose residues in myoblast aggregation. A parallel developmental study of genetic muscular dystrophy revealed similar GSL levels and enzyme activities. A larger proportion of lactosylceramide in dystrophic muscle throughout development suggests a developmental lag in the mutant.

Aging↗

PubMed1993

First appearance, distribution, and origin of macrophages in the early development of the avian central nervous system.

A phagocytic cell system of hemopoietic origin exists in the early avian embryo (Cuadros, Coltey, Nieto, and Martin: Development 115:157-168, '92). In this study we investigated the presence of cells belonging to this system in the central nervous system (CNS) of chick and quail embryos by using both histochemical staining for acid phosphatase and immunolabelling with antibodies recognizing cells of quail hemangioblastic lineage. The origin of these cells was traced in interspecific chick-quail yolk sac chimeras. Hemopoietic cells were detected within the CNS from developmental stage HH15 on, and steadily increased in number at subsequent stages. Analysis of yolk sac chimeras revealed that most of these cells were of yolk sac origin, although some hemopoietic cells of intramebryonic origin were also found in the CNS. Immunocytochemical, histochemical, and ultrastructural characterization allowed us to identify hemopoietic cells in the CNS as macrophages. These cells were consistently found in the brain vesicles and spinal cord, appearing (1) between undifferentiated neuroepithelial cells at dorsal levels of the CNS; (2) in areas of cell death; (3) in the marginal layer in close relationship with developing axons; (4) in large extracellular spaces in the subventricular layer; (5) on vascular buds growing through the marginal and subventricular layers; and (6) in the ventricular lumen. Macrophages in different locations varied in morphology and ultrastructure, suggesting that in addition to their involvement in phagocytosis, they play a role in other processes in the developing CNS, such as axonal growth and vascular development. The first macrophages migrate to the CNS independently of its vascularization, apparently traversing the pial basal lamina to reach the nervous parenchyma. Other macrophages may enter the CNS together with vascular buds at subsequent stages during CNS vascularization.

Acid Phosphatase↗

PubMed2003

Mechanisms controlling early development of the liver.

Over the last decade significant advances have been made in our understanding of the molecular mechanisms that control early aspects of mammalian liver development. Studies using tissue explant cultures and molecular biology techniques as well as the analysis of transgenic and knockout mice have identified signaling molecules and transcription factors that are necessary for the onset of hepatogenesis. This review presents an overview of these studies and discusses the role of individual factors during hepatic development.

Animals↗

PubMed1990

Expression of nerve growth factor receptor mRNA during early development of the chicken embryo: emphasis on cranial ganglia.

In situ hybridization with beta-nerve growth factor receptor (NGF-R) oligonucleotide probes was used to study NGF-R mRNA expression in early chicken embryos. Sections through the region of the visceral arches showed high levels of NGF-R mRNA in mesenchyme of the visceral arches, neural tube and myotomes. Labelling was also seen over E3 primordium of the trigeminal ganglion (V) and in the placodal thickening of the petrosal (IX) and nodose (X) ganglionic primordia. In the E5 embryo, all cranial sensory ganglia (V, VII, VIII, IX, X) expressed NGF-R mRNA although at varying levels with higher levels in the ganglia of the Vth, IXth and Xth cranial nerves than in ganglia of the VIIth and the VIIIth nerves. Within ganglia of the Vth, IXth and Xth cranial nerves, levels of NGF-R mRNA were higher in regions containing placode-derived neurons, than in regions with neural-crest-derived neurons. The placode-derived nodose ganglion (X) expressed NGF-R mRNA at all stages of development. In the E15 embryo and later in development, two thirds of the large neuron-like cells expressed high levels of NGF-R mRNA. Our results show that expression of NGF-R mRNA, in peripheral neurons, is not restricted to cells of neural crest origin. We also show a transient expression of NGF-R mRNA early in development in a wide range of non-neuronal differentiating cells. The high level of NGF-R mRNA in early differentiating tissues suggest that the NGF-R plays a wider role during development than previously anticipated.

Animals↗

PubMed1996

Larval and imaginal pathways in early development of Drosophila.

In holometabolous development, higher insects have two different life forms, the larva and the imago. Both larval and imaginal cells are derived from cells of the blastoderm stage. After the final embryonic wave of mitosis, however, only the imaginal cells remain diploid, proliferate massively and do not differentiate until metamorphosis. The separation of these two pathways was described by many authors as a fundamental process that must take place at a very early stage of development, most probably the blastoderm stage. Mainly by using single cell transplantations at the blastoderm or early gastrula stages, respectively, we found common cell lineages between larval and imaginal structures by clones overlapping in the ectoderm (i.e. larval epidermal cells and imaginal discs within a segment, or larval and imaginal salivary gland cells), the mesoderm (i.e. larval somatic muscles and adepithelial cells), and the endoderm (i.e. larval and imaginal midgut cells). From these findings we conclude that it seems to be a principle in Drosophila embryogenesis that the separation of larval and imaginal pathways is postponed to a later developmental stage.

Animals↗

PubMed1984

Early development and tissue-specific patterns of insulin binding in chick embryo.

We studied the development of insulin binding to its receptor in chick embryos from days 2-18 of the 21-day incubation period. Using partially purified membrane preparations we found that insulin receptors on both brain and liver of day 18 embryos were typical insulin receptors by multiple criteria. Specific insulin binding to preparations of whole embryos was not detected on day 2, but was present by day 3. Insulin receptors were present on both heads and bodies of embryos by day 4. Binding to liver and brains increased with development between days 8 and 18; however, the patterns of increase in the two tissues were quite distinct. In liver, binding was low on day 8, but increased markedly by day 14 (P less than 0.01). Increases after day 14 were less impressive. In contrast, binding to brain preparations was relatively well established by day 8 and did not change significantly between days 8 and 14. An abrupt increase occurred between days 14 and 16 (P less than 0.01), and a second increase took place between days 16 and 18. We have previously shown that insulin is present in chick embryos before known pancreatic development. The current demonstration that insulin receptors are also present early in embryogenesis makes it possible that insulin may influence the embryo at early stages. In addition, the different patterns of increases in insulin binding in liver and brain during mid- to late development suggest complex and tissue-specific mechanisms of regulation.

Animals↗

PubMedDate not supplied

Body axis determination during early development in amphibians.

The specification of the main axes of the body is a phenomenon based on cell communication and is among the early crucial events of embryonic development. Upon fertilization, the amphibian egg reorganizes its cytoplasmic content, leading to the establishment of the future dorsal-ventral axis of the body. Heterogeneous distribution of maternal components confers cellular regionalization after only a few mitoses. Development up to the 4000-cell stage proceeds almost entirely on maternal materials, and during this period there is remodeling of the chromatin to set up specific gene expression in various regions of the embryo. The zygote at this stage has already undertaken cellular interactions leading to mesoderm formation and regionalization. Dorsal mesodermal components then induce the formation of the Spemann's organizer, a structure directly involved in the specification of the anterior-posterior axis of the embryo (head to tail). Molecular analysis of these phenomena has allowed the identification of growth-factor-like and transcription-factor-like proteins that have characteristics typical of specification factors. We will review the recent advances on these molecules and will also discuss the putative role of retinoic acid as a posteriorizing agent.

Animals↗