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At least 1,369 records · Page 76Linked to original sources
PubMed1995

Tissue-specific regulation of muscarinic acetylcholine receptor expression during embryonic development.

We used solution hybridization, immunoprecipitation, and immunoblot analyses to examine the developmental expression of chicken m2 (cm2), cm3, and cm4 muscarinic acetylcholine receptor (mAChR) mRNA and protein in embryonic and post-hatched chick heart and retina in order to correlate developmental expression patterns with known physiological events. cm2 is the predominant mAChR subtype expressed in chick heart. cm3 and cm4 protein and mRNA expression is very low in chick heart, and cm3 expression is highest early in development. The decrease in cm3 expression correlates well with the developmental decrease in mAChR-mediated activation of phospholipase C. cm4 is the predominant mAChR subtype expressed in chick retina. The expression of both cm4 protein and mRNA is highest early in development and decreases as development progresses. cm2 and cm3 mAChR are expressed at approximately equivalent levels and have similar patterns of expression. The cm2 and cm3 protein levels increase throughout development, while cm2 and cm3 mRNA levels peak at embryonic day 15 and then decrease after hatching. Our data indicate that the three mAChR subtypes are differentially regulated in chick heart and retina and that the patterns of expression of mAChR may be important in the development and physiology of these tissues.

Aging↗
PubMed1993

Presence of the factor that inhibits collagen synthesis and stimulates cell proliferation in developing embryonic chick skin extracts.

The effects were studied of the extracts prepared from 10- and 18-day developing chick skins on collagen synthesis and proliferation of the monolayered fibroblasts established from 10-day skin. Cell proliferation was stimulated by both 10- and 18-day skin extracts at the concentration of 3.5 micrograms/ml. Collagen synthesis was suppressed by the treatment of extracts prepared from both 10- and 18-day skins at the concentration of 3.5 micrograms/ml, to a greater extent in 18-day extract. The results indicate that skin extracts possess factors exhibiting both a stimulating effect on cell proliferation and an inhibitory effect on collagen synthesis.

Animals↗
PubMedDate not supplied

Delayed replication of Marek's disease virus following in ovo inoculation during late stages of embryonal development.

Several oncogenic and non-oncogenic isolates of Marek's disease virus (MDV) were inoculated into embryonated eggs on embryonation day (ED) 16 to 18, and embryos or chicks hatching from inoculated eggs were examined for infectious virus and viral internal antigen (VIA) in lymphoid organs. There was no evidence of extensive replication of MDV in any of the embryonic tissues examined. Levels of VIA peaked 4-5 days after chicks hatched. This indicated that MDV remained inactive during embryonation and did not initiate pathogenic events until chicks hatched. Because HVT replicated rapidly in the embryo but MDV did not, in ovo inoculation of HVT simultaneously with oncogenic MDV or several days after MDV resulted in significant protection (P less than 0.025) of hatched chicks against Marek's disease (MD). Little protection was obtained if HVT was given simultaneously with MDV or after MDV to chicks already hatched. The relative susceptibility of the embryo to extensive replication of the vaccine virus but not the challenge virus apparently accounted for protection against MD in chicks hatching from dually infected eggs.

Animals↗
PubMed1983

The distribution of plasma proteins during early embryonic development in the sheep.

The distribution of the five plasma proteins that are quantitatively most important during development in the sheep has been studied in embryos of 15 to 21 days gestation. The three primary embryonic layers and tissues that differentiate from them were tested for the presence of alpha-fetoprotein (AFP), fetuin, albumin, transferrin and alpha 1-antitrypsin using the indirect immunoperoxidase method. Fetuin was the most prominent of these proteins particularly in the developing central nervous system. Fetuin and transferrin appeared early in the differentiating mesoderm and, with albumin and AFP, were detected in tissues originating from all three layers during the course of development. alpha 1-Antitrypsin appeared to have a limited distribution. All five plasma proteins were detected before the establishment of a circulatory system. It is suggested that their appearance in embryonic tissue is related to its stage of development and that they play an important part in early differentiation.

Albumins↗
PubMed2003

Epigenetic reprogramming in early embryonic development: effects of in-vitro production and somatic nuclear transfer.

A considerable proportion of offspring, in particular in ruminants and mice, born from nuclear transfer (NT)-derived and in-vitro-produced (IVP) embryos is affected by multiple abnormalities of which a high birthweight and an extended gestation length are the predominant features; a phenomenon that has been called 'large offspring syndrome' (LOS). The underlying mechanisms are largely unknown at present, but alterations of epigenetic modifications of embryonic and fetal gene expression patterns, primarily caused by alterations in DNA methylation are thought to be involved in this syndrome. In mammals, DNA methylation is essential for the regulation of transcription during development and differentiation. This review summarizes results from studies in which mRNA expression patterns from IVP and NT-derived embryos were compared with those of their in-vivo counterparts. Numerous aberrations have been found ranging from suppression of expression to de-novo overexpression or more frequently to a significant up- or down-regulation of a specific gene. These observations emphasize the need for further epigenetic studies during preimplantation embryo development to gain insight into the molecular regulation correlated with an undisturbed embryonic and fetal development. Understanding molecular mechanisms will aid improvements in biotechnologies applied to early embryos in all species, including humans.

Animals↗
PubMed1995

Impact of erythrocytes on mouse embryonal development in vitro.

To elucidate the role of reactive oxygen species (ROS) in the development of mouse embryo, effects of superoxide dismutase (SOD), catalase and erythrocytes were studied in vitro. Oocytes were fertilized and 2-cell-cleaved embryos were cultured in the presence or absence of either erythrocytes, SOD or catalase. Under standard culture conditions, the fertilization and cleavage rates were 77.4 and 12.5%, respectively. In the presence of xanthine and xanthine oxidase, those rates decreased to 28.2 and 4.5%, respectively. The hazardous effect of ROS was completely inhibited by erythrocytes. These results suggested that small amounts of erythrocytes might effectively degrade ROS during the development of cultured embryos.

Animals↗
PubMedDate not supplied

Perspectives in steroid hydroxylase gene expression: novel sites of expression during embryonic development.

CYP17 is not expressed in adult mouse adrenal glands but is expressed in a subset of fetal adrenocortical cells, indicating the potential to produce both corticosterone and cortisol during murine embryogenesis. CYP11A is expressed in the fetal adrenal but also in developing hindgut, which will form the colon, and in cells located beneath the skin of the embryo. Novel sites of expression of CYP17 and CYP11A in the mouse embryo suggest potential physiological roles for local production of steroids in diverse organs systems during development.

Adrenal Glands↗
PubMed1989

Fibroblast growth factor and transforming growth factor beta in early embryonic development.

Growth factors are known to have pleiotropic effects on many cell types ranging from the control of cell proliferation to inducing cell differentiation. FGF and TGF beta are members of two growth factor families which are thought to be involved in embryogenesis of the frog, Xenopus laevis. These two growth factors are equivalent to the embryonic "morphogen(s)" which induce one of the first differentiation events during embryogenesis, the formation of the mesoderm. Embryonic induction events are crucial for the development of most organisms and, therefore, these growth factors may be involved in induction events during mammalian embryogenesis. Thus, the structure and function of TGF beta and FGF molecules appear to be conserved throughout vertebrate evolution and during ontogeny, growth factors and their signalling pathways may be used for different functions depending upon the nature of the target cell.

Animals↗
PubMed1988

Early pregnancy wastage: relationship between chorionic vascularization and embryonic development.

The chorionic villous vascularization of 40 patients with first trimester spontaneous abortion was compared with that of 10 patients undergoing legal abortion (control group). The spontaneous abortion group was subdivided into a group with intrauterine embryonic death (n = 20) and a group with blighted ova (n = 20). Villous vascularization appeared unaffected after prolonged postmortem intrauterine retention. The incidence of vascularized villi was 89% in the control group, 26% in the group with embryonic death, and 9% in the group with blighted ova. In addition, the vascular density of vascularized villi was three to four times higher in the control group than in the two spontaneous abortion groups. The present study provides evidence that, in case of embryonic death and blighted ova, chorionic villous vascularization is deficient.

Abortion, Spontaneous↗
PubMed1991

Effects of low-frequency magnetic fields on embryonic development and pregnancy.

Experimental and epidemiologic studies on the effects of low-frequency magnetic fields on pregnancy are reviewed. The literature suggests that these fields have adverse effects on chick embryo development. The interaction mechanism is not known. The results of experiments with mammals are inconsistent. There is more evidence of effects on mice than on rats, and the data suggest that fetal loss might be increased rather than malformations. Most of the epidemiologic studies related to pregnancy and low-frequency magnetic fields have concerned operators of a video display terminal (VDT). The results do not provide evidence for an association between adverse pregnancy outcome and use of a VDT. Other (stronger) sources of low-frequency magnetic fields have been addressed in only a few studies. It is not yet possible to conclude whether occupational or residential exposure to low-frequency magnetic fields affects human prenatal development. There is an apparent need for further investigation.

Animals↗
PubMed1998

p75NTR and Trk receptors are expressed in reciprocal patterns in a wide variety of non-neural tissues during rat embryonic development, indicating independent receptor functions.

The p75 kDa neurotrophin receptor (p75NTR) has been detected in a number of non-neural tissues, especially during development. Reports of Trk receptor transcripts in non-neural tissues raise the possibility that the sites of p75NTR expression during development may correlate with Trk receptor expression. Coexpression of p75NTR with the Trk receptors in developing non-neural tissues would support the hypothesis that there is a cooperative function between the two receptor subclasses. To address these questions, p75NTR was localized relative to the three known Trk receptors in adjacent sections of rat embryos at stages of development when the highest levels of p75NTR have been observed in the muscle, maxillary pad, kidney, and lung. Using in situ hybridization and immunhistochemical analyses, we show here that the Trk receptors are expressed extensively in non-neural tissues during cell differentiation and tissue morphogenesis but in patterns that are generally reciprocal to that of p75NTR. The results indicate p75NTR most likely functions independently of the Trk receptors in most developing non-neural tissues. However, the p75NTR consistently appears in non-neural cells adjacent to those expressing Trk receptors. The reciprocal patterns of expression indicate that the separate activities of the two receptors most likely complement each other in regulating cell-cell interactions important for the innervation of developing non-neural tissues.

Animals↗