Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Embryonic Induction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 307 records · Page 17Linked to original sources
PubMed2006

Use of lectins for probing differentiated human embryonic stem cells for carbohydrates.

The carbohydrates present on the surface of differentiated human embryonic stem cells (hESCs) are not yet well established. Here, we have employed a panel of lectins and several anti-carbohydrate antibodies to determine the carbohydrates that are present at day 12 of hESC differentiation as embryoid bodies (EBs). On the basis of staining with fluorescein-labeled lectins, we have determined the presence of both terminal and internally linked alpha-d-mannopyranosyl groups, poly-N-acetyllactosaminyl chains, both alpha2,3- and alpha2,6-linked N-acetylneuraminic acid (Neu5Ac), alpha1,6-linked l-fucosyl, and beta-D-galactosyl groups, and more specifically, the T, Tn, and sialyl-Tn antigens. However, no alpha1,2-linked l-fucosyl, terminal nonreducing alpha-D-galactosyl, N-acetyl-beta-D-glucosaminyl, nor N-acetyl-alpha-D-galactosaminyl groups were found by this approach. We also established the presence of Neu5Acalpha2,3/2,6-Galbeta1,4 GlcNAc-terminated chains on the surfaces of 12-day-old EBs, as indicated by the great enhancement of staining by Erythrina cristagalli agglutinin (ECA) after treatment with neuraminidase. In each case, inhibition of binding by a haptenic sugar or treatment with neuraminidase was used to eliminate the possibility of nonspecific binding of the lectins. A comparison with undifferentiated cell staining revealed an increase in alpha2,3-linked Neu5Ac as well as a change to exclusively alpha1,6-linked l-fucose upon differentiation.

Carbohydrates↗
PubMed1991

Peptide growth factors and proto-oncogenes in mammalian conceptus development.

Development of mammalian conceptuses (embryo and associated membranes) in utero is an extremely complex, programmed orchestration of cellular activities that include proliferation, differentiation, migration, and death. Failure of conceptuses to develop is a significant, though not well-understood, problem in human and animal reproduction. Increased understanding of molecular and cellular processes in these events is ultimately required to determine the mechanisms responsible for developmental failures. Peptide growth factors, their associated proteins (carrier proteins and membrane receptors), and proto-oncogenes (the normal, cellular counterparts of retroviral oncogenic proteins) are intimately involved in normal and abnormal cellular growth regulation. This paper highlights recent work which suggests the involvement of these proteins in critical aspects of conceptus growth and uterine-conceptus interactions during the peri-implantation period.

Animals↗
PubMed1997

cash4, a novel achaete-scute homolog induced by Hensen's node during generation of the posterior nervous system.

In vertebrate embryos, the precursor cells of the central nervous system (CNS) are induced by signaling from the organizer region. Here we report the isolation of a novel vertebrate achaete-scute homolog, cash4, which is expressed in the presumptive posterior nervous system in response to such signaling. cash4 is first expressed in epiblast cells flanking the late-phase organizer (Hensen's node), which retains its ability to induce cash4 during regression to the caudal end of the embryo. We show that these node-derived signals can be mimicked in vivo by the activity of fibroblast growth factor (FGF). We demonstrate that cash4 can substitute for the achaete/scute genes in the fly and that it also has proneural activity in vertebrate embryos. Together these results suggest that cash4 functions as a proneural gene downstream of node-derived signals (including FGF) to promote the formation of the neural precursors that will give rise to the posterior CNS in the chick embryo.

Amino Acid Sequence↗
PubMed1995

Combinatorial signaling by Sonic hedgehog and Wnt family members induces myogenic bHLH gene expression in the somite.

We have demonstrated previously that a combination of signals from the neural tube and the floor plate/notochord complex synergistically induce the expression of myogenic bHLH genes and myogenic differentiation markers in unspecified somites. In this study we demonstrate that Sonic hedgehog (Shh), which is expressed in the floor plate/notochord, and a subset of Wnt family members (Wnt-1, Wnt-3, and Wnt-4), which are expressed in dorsal regions of the neural tube, mimic the muscle inducing activity of these tissues. In combination, Shh and either Wnt-1 or Wnt-3 are sufficient to induce myogenesis in somitic tissue in vitro. Therefore, we propose that myotome formation in vivo may be directed by the combinatorial activity of Shh secreted by ventral midline tissues (floor plate and notochord) and Wnt ligands secreted by the dorsal neural tube.

Animals↗
PubMed1990

Relationship between Merkel cells and nerve endings during embryogenesis in the mouse epidermis.

Close relationships between Merkel cells (MC) and nerve endings (NE) exist in the adult mouse. Because MC may serve as targets for the ingrowth of NE during embryogenesis, the purpose of the present study was to analyze the relationship between MC and NE during embryogenesis. Frozen tissue from whisker pads and backs of NMRI mouse embryos (12-17 d gestational age) were studied by double-labeling indirect immunofluorescence (IIF) with a cytokeratin monoclonal antibody that recognizes MC and with a neurofilament anti-serum. Such an approach allowed the analysis of a large number of MC (up to 5000), thus yielding quantitative data. At day 12 of gestational age, no MC were observed by IIF. From day 13 to 17, the number of MC, as well as their association with NE, progressively increased. On day 13, only 57% of whisker pad MC were NE associated, whereas by day 17, 95% were NE associated. These results were confirmed by electron microscopic (EM) observations. On the back, the same chronologic relationship between MC and NE was observed, but was later in the course of embryogenesis. There was also a time- and zone-dependent increase in MC association with NE in the epidermal zones studied (isthmic, parafollicular, interfollicular). These observations 1) establish the time course of MC and NE contacts during embryogenesis in the mouse epidermis, 2) show that MC are present in the epidermis and appendages before NE reach the epithelium, and 3) support the hypothesis that MC could act as targets for the growing NE.

Animals↗
PubMed1978

The stability of vitamin A-induced metaplasia of mouse vibrissa follicles in vitro.

Tests were made of the stability of the previously described glandular morphogenesis and mucous metaplasia of embryonic mouse vibrissa follicles produced in vitro by excess vitamin A. The changes in individual follicles were observed in living tissue explants and serial sections. Upper lip skin of 13.5-day embryos underwent budding from vibrissa follicles to form branching glands which secreted mucus after 10--14 days in medium containing 4.7 microgram/ml retinol. If this medium was replaced with standard medium after 7 days, glandular morphogenesis and metaplasia continued unaffected, although some hair follicle bases returned to their original morphogenetic program. Similar results were obtained with skin of 13-day embryos treated with vitamin A (6.0 MG/ML) for only 3 days. The moderate degree of glandular morphogenesis in 15-day skin with vitamin A (4.7 microgram/ml) was not altered by the simultaneous addition of a high dose of cortisol (18 microgram/ml). It is suggested that the initiation of glandular morphogenesis of follicles differs from the initiation of mucous metaplasia in embryonic chick epidermis by vitamin A, in that it resembles a new secondary embryonic induction rather than a modulation of the epithelium.

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↗
PubMed1998

Common molecular pathways in skeletal morphogenesis and repair.

The formation of bone is a continual process in vertebrate development, initiated during fetal development and persisting in adulthood in the form of remodeling and repair. The remarkable capacity of skeletal tissues to regenerate has led to the hypothesis that the molecular signaling pathways regulating skeletogenesis are shared during fetal development and adult wound healing. A number of key regulatory pathways that are required for endochondral ossification during fetal development are described, and their reintroduction in fracture repair demonstrated. Secreted proteins such as Sonic and Indian hedgehog exert their effect on pattern formation and chondrogenesis in the appendicular skeleton, partly through regulation of molecules such as bone morphogenic proteins (Bmps) and parathyroid hormone-related peptide (PTHrP). Once chondrocytes have matured and hypertrophied, they undergo apoptosis and are replaced by bone; the transcription factor Cbfal plays a critical role in this process of chondrocyte differentiation and ossification. Analyses of the expression patterns of these genes during fracture healing strongly suggest that they play equivalent roles in adult wound repair. Knowledge acquired through the study of fetal skeletogenesis will undoubtedly contribute to an understanding of fracture repair, and subsequently guide the development of biologically based therapeutic interventions.

Animals↗
PubMed2001

Embryo effects in human implantation: embryonic regulation of endometrial molecules in human implantation.

Embryonic implantation requires coordinated development of the blastocyst and the maternal endometrium. Considerable advances have been made in the understanding of the cell biology of human embryo and maternal endometrium as separate entities. Nevertheless, communication between them and their reciprocal effects on each other constitute an exciting and as-yet unsolved problem in reproductive medicine. Cross-talk among the embryo, endometrium, and the corpus luteum are known to occur in ruminants and primates; more specifically, endometrial-embryonic interactions have been reported in rodents and primates. Here, we present updated information in humans on the embryonic regulation of endometrial epithelial molecules such as chemokines, adhesion molecules, antiadhesion molecules, and leptin during the apposition and adhesion phases of human implantation. Also the embryonic induction of apoptosis in endometrial epithelial cells as a mechanism for crossing the epithelial barrier will be described.

Apoptosis↗
PubMed1996

Cholesterol modification of hedgehog signaling proteins in animal development.

Hedgehog (Hh) proteins comprise a family of secreted signaling molecules essential for patterning a variety of structures in animal embryogenesis. During biosynthesis, Hh undergoes an autocleavage reaction, mediated by its carboxyl-terminal domain, that produces a lipid-modified amino-terminal fragment responsible for all known Hh signaling activity. Here it is reported that cholesterol is the lipophilic moiety covalently attached to the amino-terminal signaling domain during autoprocessing and that the carboxyl-terminal domain acts as an intramolecular cholesterol transferase. This use of cholesterol to modify embryonic signaling proteins may account for some of the effects of perturbed cholesterol biosynthesis on animal development.

Animals↗
PubMed1999

Differences in left-right axis pathways in mouse and chick: functions of FGF8 and SHH.

A molecular pathway leading to left-right asymmetry in the chick embryo has been described, in which FGF8 is a right determinant and Sonic Hedgehog a left determinant. Here evidence is presented that the Fgf8 and Sonic Hedgehog genes are required for left-right axis determination in the mouse embryo, but that they have different functions from those previously reported in the chick. In the mouse FGF8 is a left determinant and Sonic Hedgehog is required to prevent left determinants from being expressed on the right.

Animals↗
PubMed1997

HNF4beta, a new gene of the HNF4 family with distinct activation and expression profiles in oogenesis and embryogenesis of Xenopus laevis.

The transcription factor hepatocyte nuclear factor 4 (HNF4) is an orphan member of the nuclear receptor superfamily expressed in mammals in liver, kidney, and the digestive tract. Recently, we isolated the Xenopus homolog of mammalian HNF4 and revealed that it is not only a tissue-specific transcription factor but also a maternal component of the Xenopus egg and distributed within an animal-to-vegetal gradient. We speculate that this gradient cooperates with the vegetally localized embryonic induction factor activin A to activate expression of HNF1alpha, a tissue-specific transcription factor with an expression pattern overlapping that of HNF4. We have now identified a second Xenopus HNF4 gene, which is more distantly related to mammalian HNF4 than the previously isolated gene. This new gene was named HNF4beta to distinguish it from the known HNF4 gene, which is now called HNF4alpha. By reverse transcription-PCR, we detected within the 5' untranslated region of HNF4beta two splice variants (HNF4beta2 and HNF4beta3) with additional exons, which seem to affect RNA stability. HNF4beta is a functional transcription factor acting sequence specifically on HNF4 binding sites known for HNF4alpha, but it seems to have a lower DNA binding activity and is a weaker transactivator than the alpha isoform. Furthermore, the two factors differ with respect to tissue distribution in adult frogs: whereas HNF4alpha is expressed in liver and kidney, HNF4beta is expressed in addition in stomach, intestine, lung, ovary, and testis. Both factors are maternal proteins and present at constant levels throughout embryogenesis. However, using reverse transcription-PCR, we found the RNA levels to change substantially: whereas HNF4alpha is expressed early during oogenesis and is absent in the egg, HNF4beta is first detected in the latest stage of oogenesis, and transcripts are present in the egg and early cleavage stages. Furthermore, zygotic HNF4alpha transcripts appear in early gastrula and accumulate during further embryogenesis, whereas HNF4beta mRNA transiently appears during gastrulation before it accumulates again at the tail bud stage. All of these distinct characteristics of the newly identified HNF4 protein imply that the alpha and beta isoform have different functions in development and in adult tissues.

Amino Acid Sequence↗
PubMed1978

Waardenburg syndrome with a fixed dilated pupil.

An unusual case of Waardenburg syndrome associated with a detailed and fixed pupil of the lighter eye is described. Pharmacological investigations were performed to localise the site of the pupillary lesion. A lack of cholinergic reactivity was demonstrated, possibly due to congenital agenesis of the sphincter pupillae. Sympathetic activity was not impaired. Spiral ganglion agenesis and midline congenital anomalies are common features in Waardenburg syndrome. These lesions as well as the fixed dilated pupil might be due to an embryonal inductive failure.

Abnormalities, Multiple↗
PubMed1998

Direct and mediated effects of testosterone: analysis of sex reversed mosaic mice heterozygous for testicular feminization.

Sex reversed mice are XX males carrying on one of their X chromosomes a translocation of the sex determining region of the Y (Cattanach's Sxr factor). The phenotype corresponds to the Klinefelter syndrome in man. The X linked Tfm (testicular feminization) mutation in the mouse is a frame shift in the androgen receptor gene leading to complete androgen insensitivity. Due to random X inactivation, sex reversed mice heterozygous for Tfm, are mosaics composed of a variable proportion of androgen insensitive X Tfm and androgen sensitive X+ wildtype cells. In the intersexual genital tract, Tfm cells are maintained as undifferentiated cells in the epididymal duct. To the distorted prostate lobes and bulbourethral glands they contribute some lobules of indifferent urethral glands. A large contribution of Tfm cells allows downgrowth of Wolffian and Müllerian ducts to form a vagina. In the external genitalia the stimulatory effect of testosterone is reduced leading to various degrees of feminization correlating with the proportion of Tfm cells present. In the mosaics effects of testosterone, mediated by local growth factors from the wildtype to the Tfm cells, can be distinguished from direct effects expressed only in the wildtype cells. Mediated effects are embryonic induction and morphogenesis of male organs and postnatal maintenance of organ structure and proliferation. The direct effect is cellular differentiation.

Androgen-Insensitivity Syndrome↗
PubMed1999

Epithelial-mesenchymal interactions in development of the mouse fetal genital tubercle.

Epithelial-mesenchymal interactions play a central role in the development of urogenital organs. We hypothesized that normal development of the external genitalia depends upon proper mesenchymal-epithelial signaling. The mesenchyme of the adult mouse penis consists of a corpus cavernosum and proximal and distal bones. The differentiation of penile mesenchyme into bone and cartilage begins after birth and can be accelerated by androgens. After determining the sex, genital tubercles of fetal mice at gestational day 15 were removed. The genital tubercles were trypsinized and microdissected to remove the epidermis and urethra from the mesenchyme. Recombinant specimens were created by combining genital tubercle mesenchyme with genital tubercle epithelium, bladder epithelium or tail epidermis. Tissues were grafted under the renal capsule of male athymic mice. After 3 weeks of growth, grafts were removed from the kidney, weighed and stained with hematoxylin and eosin, Alcian blue and peanut agglutinin. Male and female grafts showed no difference in growth or differentiation. Intact grafts and recombinant grafts, irrespective of the epithelial source, grew significantly more than grafts of the mesenchyme only. Recombinant grafts demonstrated a significantly higher prevalence of cartilage formation and mesenchymal differentiation compared to grafts of the mesenchyme without epithelium. Since heterologous epithelium is able to induce equivalent growth and differentiation of phallic mesenchyme, epithelium carries a permissive, but critical, role in genital mesenchyme development.

Animals↗
PubMed1999

Prenatal development of the alveolar bone of human deciduous incisors and canines.

The formation of the human alveolar process around the incisors and canines is a hitherto unreported aspect of fetal oral development. The question is how, where, and when the alveolar process is formed. The purpose of this study was to elucidate the questions where and when and hence to analyze the pattern of formation of the alveolar bone around developing human deciduous canine and incisor teeth. The study was conducted with material selected from a sample of 61 normal human fetuses, legally or spontaneously aborted. Fertilization ages ranged from 9 to 22 weeks, crown-rump Length from 25 to 205 mm, and foot length from 4 to 34 mm. From this material, 7 maxillae and 10 mandibles were selected for the study according to developmental stages of the canines and incisors and according to the orientation of the histological sections. The skeletal investigation consisted of macroscopic and microscopic analysis of the mandibles and maxillae. The investigations revealed the absence of bone between the central and lateral incisors in the mandibles and maxillae of fetuses below the ages of 21 and 22 weeks, respectively. In three specimens, alveolar bone between the central and lateral incisors was recorded (21, 21, and 22 weeks of fertilization). Absence of bone labial to the canine was recorded in all fetuses investigated. In all other regions, alveolar bone occurred as a regular finding. The present study has shown that alveolar bone formation is strictly coordinated with tooth formation. Alveolar bone occurs later in the area labial to the canine and in the region between the central and lateral incisors than it does in other areas associated with the incisor/canine regions. Knowledge of this pattern in the formation of the alveolar process seems to be of importance for a future elucidation of how the alveolar process is initially formed.

Alveolar Process↗