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At least 19 recordsLinked to original sources
PubMed1988

[Growth factors and embryonic development].

Embryonic development involves five major cellular events: division, migration, selective cell-cell contact, differentiation and planned cell death. Among these numerous cellular events the growth factors play a major role in regulating cell growth and differentiation by an autocrine or paracrine mechanism. The growth factors may be defined as polypeptides that stimulate cell proliferation directly through binding to specific high affinity cell membrane receptors. The best characterized group of growth factors includes the epidermal growth factor (EGF), platelet-derived growth factor (PDGF), insulin and insulin-like growth factors (IGF) and the transforming growth factors TGF alpha and TGF beta. These factors are chemically characterized by their requirement for intact disulfide bridges for biological activity and have a very broad target cell specificity. A second group of polypeptide growth factors includes fibroblast growth factors (FGF) which bind specifically to heparin and induce angiogenesis both in vivo and in vitro. Their ability to stimulate cell proliferation is mainly restricted to cells from mesodermal and neuroectodermal origin, including endothelial cells. Some very small peptides, called neuropeptide-like growth factors have been recently described. The role of these growth factors during embryogenesis is studied in vivo in mouse embryos or in Xenopus eggs or in vitro in cell cultures such as murine or human teratocarcinoma cells. Some of these growth factors such as PDGF or TGF beta are chemotactic agents, and are able to modify the extracellular matrix improving the cell migrations. For example in the Xenopus, EGF and TGF beta induce the mesoderm from the ectoderm before gastulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of exogenous corticosterone on chicken embryonic development.

Embryonic corticosterone (CS) levels were altered by dipping 3-day-old fertile Leghorn eggs in 0, .01, .05, and 1% CS dissolved in absolute ethanol. Mortality was determined by candling from Day 4 through hatch. Body weights and serum CS were measured daily from Day 14 until hatch. Embryos of eggs dipped in 1% CS in ethanol solution had reduced circulating CS. Embryo weights were reduced and mortality increased as concentration of hormone increased. A CS peak was observed just before hatch for control, .01 and .05% groups, but not for the .1% group. All embryos in the .1% treatment group died before hatch. The importance of embryonic CS for normal development and hatching was indicated.

Animals↗
PubMed1986

Changes in insulin binding to developing embryonic chick neural retina cells.

Specific cell surface insulin binding to embryonic chick neural retina cells has been demonstrated in vivo. Kinetics of insulin binding as well as hormonal specificity were similar to those reported for other vertebrate cells and tissues, both neural and nonneural. When surface insulin binding to retinal cells was studied as a function of embryonic age, a developmental relationship was observed. Scatchard analysis revealed that the number of cell surface insulin receptors decreased approximately 75% between days 10 and 16 of embryonic development. Receptor affinities remained fairly constant for this period.

Animals↗
PubMed1989

Extracellular matrix, cell skeletons, and embryonic development.

During embryonic development, the extracellular matrix (ECM) promotes the production of differentiated products by epithelial cells and the migration of mesenchymal cells, and probably also plays a role in epithelial-mesenchymal transformation. Here we examine the role of the cell skeleton (actin, microtubules, intermediate filaments) in mediating matrix effects on mesenchymal cell morphology, migration, and formation. The interaction of both epithelial cells and mesenchymal cells with ECM seems to involve the actin cortex, which is best developed in the base of the epithelial cell, where it attaches to underlying matrix via membrane-intercalated receptors. To interact with the matrix, the fibroblast has appropriate ECM receptors and an actin cortex around the whole cell. The actin cortex is absolutely required for assumption of bipolar shape, elongation, and movement through the matrix. Since the cortex seems to be anchored to the matrix, it is unlikely that it moves during cell migration. A new hypothesis states that the microtubule- and intermediate filament-rich endoplasm, containing the nucleus, moves past the actin cortex-receptor-matrix complex into the newly synthesized front end of the mesenchymal cell to effect forward movement. When epithelial cells transform into mesenchyme in the embryo, or when they are induced to do this in vitro, they switch from the keratin intermediate filament profile to one rich in vimentin, and the effect of cell matrix interaction on cell shape is profoundly altered. Vimentin-actin interactions with ECM may be a major factor in the ability of a cell to become mesenchymal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of Xenopus laevis. I. Embryonic development.

An immunohistochemical study of the localization of cytotactin and cytotactin-binding (CTB) proteoglycan throughout embryonic development of the anuran Xenopus laevis reveals that both appear in a restricted pattern related to specific morphogenetic events. CTB proteoglycan expression is first detected during gastrulation at the blastopore lip. Later, it is seen in the archenteron roof around groups of cells forming the notochord, somites and neural plate. Cytotactin first appears after neurulation, and is restricted to the intersomitic regions. Both molecules appear along the migratory pathways of neural crest cells in the trunk and tail. Later, cytotactin is present at sites where neural crest cells differentiate, around the aorta and in the smooth muscle coat of the gut; CTB proteoglycan is absent from these sites. In the head, cytotactin is initially restricted to the regions between cranial somites, while CTB proteoglycan is distributed throughout the cranial mesenchyme. The expression of both molecules is later associated with key events in chondrogenesis during the development of the skull. After chondrogenesis, CTB proteoglycan is distributed throughout the cartilage matrix, while cytotactin is restricted to a thin perichondrial deposit. Both molecules are expressed in developing brain. These findings are compared to studies of the chick embryo and although distinct anatomical differences exist between frog and chick, the expression of these molecules is associated with similar developmental processes in both species. These include mesoderm segmentation, neural crest cell migration and differentiation, cartilage development, and central nervous system histogenesis.

Animals↗
PubMed1992

Effects of three methods of selection for litter size in mice on pre-implantation embryonic development.

Characteristics of preimplantation embryonic development to Day 3.5 of gestation were evaluated in lines of mice after 21 generations of selection for litter size or components of litter size. Selection criteria were direct selection for number born (LS), selection on an index of ovulation rate and the proportion of ova shed that resulted in fully formed pups (IX), selection for number born in unilaterally ovariectomized females as an indication of uterine capacity (UT), and an unselected control (LC). Comparison of the average distributions of embryonic stage of development on the left side of the uterus showed that selection (average effect of LS, IX, and UT vs. LC) tended to advance (p = 0.07) the average stage of embryonic development at Day 3.5 and shift the distribution (p = 0.10) by increasing the frequency of expanded blastocysts and decreasing the frequency of pre-morula embryos. A similar shift in the distribution on the right side of the uterus was not statistically significant. Selection decreased (p = 0.06) variability in developmental stage among embryos within the right uterine horn. These selection criteria evaluated in the mouse appear to have changed the frequencies of genes that affect some determinants of average stage of embryonic development and uniformity of development within a uterine horn at Day 3.5 of gestation.

Animals↗
PubMed1986

Hemoglobin switching during murine embryonic development: evidence for two populations of embryonic erythropoietic progenitor cells.

Explants of normal mouse embryonic tissues and disaggregated embryonic single cells were cultured in vitro to study the erythropoietic progenitor cells present during embryonic development. The results indicate that there are two populations of erythropoietic progenitor cells committed to different hemoglobin synthetic programs. These progenitor cells are present at an early gestational stage prior to the formation of the fetal hepatic primordium. One population of progenitors can be stimulated by erythropoietin alone to form usually small erythroid colonies after culture for six days in vitro. These erythroblasts primarily synthesize embryonic hemoglobins, but produce some adult hemoglobins as well. The other population of progenitors requires stimulation by both erythropoietin and adult spleen cell-conditioned medium, and usually forms large erythroid colonies after culture for six days in vitro. These erythroblasts produce only adult hemoglobins.

Animals↗
PubMed1988

Influence of nicotine and caffeine on rat embryonic development.

The influence on embryonic development of nicotine and caffeine at dose levels approximating human consumption was investigated in Sprague-Dawley rats. One group of animals received nicotine administered subcutaneously by an Alzet mini-osmotic pump from gestational day 6 through 12 (25 mg over 7 days; rate 149 micrograms/hr). Control animals received physiological saline in a similar manner. A second group received a single intravenous injection of caffeine (25 mg/kg) on gestational day 6. Control animals were treated with physiological saline. A further group received both nicotine and caffeine on gestational day 6 as described for the two previous groups. There were no significant differences among any of the groups with respect to maternal weight gain, litter size, embryolethality, fetal weight, or crown-rump length. The offspring of nicotine treated animals showed a significantly higher incidence of hydrocephaly when compared to the controls, but in the combined treatment group no malformed fetuses were observed. Light microscopic examination of maternal liver, kidney and placentas revealed changes in the hepatic sinusoids, glomeruli and intervillous spaces after nicotine and combined treatment. In addition, the decidua basalis was poorly developed compared to the controls. Chorionic villi and fetal kidney appeared normal in all groups. A coteratogenic effect is not evident from these findings.

Animals↗
PubMed1986

Changes in glucose 6-phosphate dehydrogenase activity in developing embryonic chick skeletal muscle and spinal cord.

Glucose 6-phosphate dehydrogenase (G6PDH) activity was examined in the developing embryonic chick in brachial and lumbar spinal cord and pectoral and leg muscle. Enzyme activity was generally highest at the earliest stage examined, embryonic day 5. The developmental profiles for G6PDH activity in the two muscles were similar: a sharp initial decrease occurred between days 5 and 9, with relatively low levels present by day 18; peaks of G6PDH activity at days 12 and 16 were more prominent in leg muscle. Similar levels of G6PDH were also detected in spinal cord with the developmental profile in the brachial spinal cord resembling that seen in muscle. In lumbar spinal cord, initial G6PDH activity was lower than in brachial spinal cord; the developmental profile, however, resembled that seen in the brachial spinal cord, with an initial drop in enzyme activity seen between days 5 and 7. Neural regulation of G6PDH activity in mature muscle is believed to repress enzyme synthesis. The drop in G6PDH activity observed in embryonic spinal cord and muscle between days 5 and 9 coincides with the initiation of functional neuromuscular contacts. Hence, the normal regulation of G6PDH during embryonic development may involve the repression of G6PDH in spinal cord neurons and muscle, possibly effected by their interaction.

Animals↗
PubMed1979

The biosynthesis of nicotinamide adenine dinucleotide during early stages of frog embryonic development of haploid and diploid embryos.

1. Concentration of NAD during embryonic development of haploid and diploid embryos of frog was followed. NAD content in haploid embryonic forms is twice that in diploid embryos. 2. The variation of the NMN adenylyltransferase activity in the oocytes and during the first states of embryonic development as surveyed in the nuclear soluble fraction and the nuclear insoluble fraction (chromatin). 3. The enzyme activity in the soluble fraction is low during embryonic development and shows higher values in haploid embryos. 4. In the nonfertilized mature oocytes, the NMN adenylyltransferase activity is sixfold higher in the insoluble chromatin fraction than in the soluble fraction. 5. The evolution of the NMN adenylyltransferase in the insoluble chromatin fraction also shows higher values in haploid embryos, as compared with diploid forms.

Animals↗
PubMed1985

Effect of acyclovir on mammalian embryonic development in culture.

Acyclovir [9-(2-hydroxyethoxymethyl)guanine] interfered with embryonic development in vitro when assessed with the "whole-embryo" culture technique. The "no-observed-effect level" was at 10 microM acyclovir; Minor impairment of embryonic development (retarded development of ear anlagen) was observed in vitro at 25 microM acyclovir in the culture medium. At high concentrations (100 or 200 microM) development of the ear anlagen was largely inhibited. At concentrations of 50 microM acyclovir or higher, additional disturbances of embryonic differentiation in vitro became obvious, resulting in gross structural abnormalities, especially of the brain (telencephalon); Histological examinations confirmed and extended these observations: at 100 microM acyclovir alterations of the neuroepithelium of the ventricles were pronounced, the telencephalon had developed poorly or was almost completely absent, and necroses were seen in the ear anlagen, the maxillary branch and within the somites; In a limb bud culture (mouse embryos, starting with day 11 of gestation) acyclovir interfered with the differentiation of cartilaginous bone anlagen at concentrations of 200 microM and more in the culture medium. A concentration of 100 microM induced no significant effect. Thus, this organ culture system is less sensitive to the action of acyclovir when compared with whole-embryo culture; Contrary to the results achieved with acyclovir, physiological nucleosides (2'-deoxyguanosine and 2'-deoxyadenosine) did not interfere with embryonic development in vitro even at the highest concentration tested (500 microM).

Abnormalities, Drug-Induced↗
PubMed1991

Tissue-dependent regulation of protein tyrosine kinase activity during embryonic development.

Protein tyrosine kinase activity was assayed in a variety of chicken tissues during embryonic development and in the adult. In some tissues protein tyrosine kinase activity decreased during embryonic development; however, in other tissues it remained high throughout development, it contrast to the level of protein tyrosine phosphorylation, which decreased during development. The highest levels of tyrosine kinase activity were detected in 17-d embryonic brain although only low levels of protein tyrosine phosphorylation were observed in this tissue. Several alternatives were examined in an effort to determine the mechanism responsible for the low levels of tyrosine phosphorylated proteins in most older embryonic and adult chicken tissues despite the presence of highly active tyrosine kinases. The results show that the regulation of protein tyrosine phosphorylation during embryonic development is complex and varies from tissue to tissue. Furthermore, the results suggest that protein tyrosine phosphatases play an important role in regulating the level of phosphotyrosine in proteins of many older embryonic and adult tissues.

Animals↗
PubMed1975

A rapid spectrophotometric method for the monitoring of embryonic development in ticks (Acarina: Ixodoidea).

A rapid spectrophotometric method for the monitoring of embryonic development in Boophilus decoloratus (Koch, 1844) is described. The method is based on a quantitative assessment of guanine, the prinicipal end-product of nitrogenous metabolism in ticks, which is gradually built up and stored in the rectal sac during embryonic development of the larvae. A study of the growth of tick embryos under constant temperature conditions and 6 different humidity conditions demonstrated that embryonic development was dependent on the water content of the eggs at the time of oviposition. When eggs lost more than 35% of their initial mass through evaporation, nitrogenous metabolism (as indicated by guanine production) was seriously affected and embryos died.

Animals↗
PubMed1992

Insulin and insulinlike growth factors in embryonic development. Effects of a biologically inert insulin (guinea pig) on rat embryonic growth and development in vitro.

Congenital anomalies occur up to four times more frequently in diabetic pregnancy than in the nondiabetic population. Although past work has shown that maternal hyperglycemia and hyperketonemia may increase embryonic abnormalities, recent experimental evidence suggests that low insulin levels may also contribute to diabetic embryopathy. This study investigated the effects of guinea pig serum (whose insulin is inactive in rat systems) on rat embryonic growth and development in culture. Supplementation of guinea pig serum with pork insulin at low (1 ng/ml) and high (5 ng/ml) physiological concentrations and insulinlike growth factors (IGF) I and II were also studied. Culture of rat embryos from the early headfold stage in guinea pig serum resulted in poor embryonic growth and development with a 92% rate of anomalies. Supplementation of guinea pig serum with zinc-binding pork insulin significantly improved rat embryonic growth and development (46% anomaly rate) especially between the first 5 and 21 h of the period of organogenesis. This evidence supports our most recent findings that low insulin levels, as encountered in untreated diabetic pregnancy, may contribute to the increased risk of congenital abnormality. Insulin at low physiological concentrations improved growth, whereas higher physiological concentrations were required to increase growth and development. IGF-I or IGF-II supplementation improved rat embryonic growth and development but failed to match that of the controls, indicating that other growth factors including insulin may also be required.

Abnormalities, Drug-Induced↗
PubMed1979

Evidence that sclerotomal cells do not migrate medially during normal embryonic development of the rat.

During embryonic development the medial part of the somite disorganizes or breaks up into sclerotomal cells which, according to many published reports, migrate medially to surround the notochord. The purpose of the study was to determine whether these cells actually migrate medially toward the notochord. Distances were measured between the notochord and the adjacent neural tube and the somite or its remnant during the period of somite disorganization. Serially sectioned, normal 10.5- to 13.5-day (d) rat embryos were used. Only transverse sections through the middle of the fourth cervical (C-4) body segment were measured, corresponding to the level of somite No. 8 (10.5 d) or its dermatomyotome remnant (10.5-11.5d) or spinal nerve C-4 (12.5-13.5d). Measurements were taken at six stages from photographic montages, all of which were made at precisely the same magnification. The notochord was the central axial structure from which the measurements were determined. The changes in distance show that during the period of somite breakup the neural tube grows dorsally, away from the notochord which lies adjacent to its ventral surface. Simultaneously the somite remnant moves laterally and dorsally, all the while maintaining its position relative to the overlying ectoderm and leaving behind a trail of sclerotomal cells. Also at each stage cell counts were made on the medial sclerotomal region of the C-4 segment. The average counts reveal that not only does the total number of cells increase substantially over the three-day period (42-7,546), but also the total number of mitoses (3.5-200), while the mitotic index decreases (9.0-2.7). High proliferative activity is apparent in the medial sclerotomal cells throughout the 3-day period. The evidence supports the conclusion that local proliferation of the trailing cells, which were left by the somite remnant as it moved dorsolaterally, causes the subsequent increase in density of the perichordal tissue, rather than an influx of migrating cells. Instead of sclerotomal cells migrating medially toward the notochord, the present study suggests that these cells retain their position relative to the notochord or central axis and that the medial sclerotomal region forms as a result of the growth movements of the surrounding structures.

Animals↗
PubMed1991

Antibodies to sperm surface antigens and the c-myc proto-oncogene product inhibit early embryonic development in mice.

The effects of antibodies against sperm antigens and the c-myc proto-oncogene product on early embryonic development were investigated in mice. Affinity-purified Fab' antibodies against lithium diiodosalicylate (LIS)-solubilized murine sperm extract and fertilization antigen (FA-1) reduced (p less than 0.01 to p less than 0.001) blastulation rates of in vitro cultured 2-cell murine embryos primarily because of an arrest of development at the morula stage. Similarly, the c-myc monoclonal antibody (mAb) affected early embryonic development in a dose-dependent manner. These effects were specific, since immunoabsorption, with its respective peptide, completely blocked the inhibitory effect of the c-myc mAb. Anti-LIS sperm Fab' identified four protein bands (approx. 36, 29, 24.6, and 17.6 kDa) on Western blots of extracts from unfertilized and fertilized ova, one band (approx. 68 kDa) each on 4-8-cell embryo and morula extracts, and one band (approx. 53 kDa) on blastocyst extracts. Anti-FA-1 Fab' did not react with unfertilized or fertilized ova, but specifically identified two protein bands (approx. 53 and 25.7 kDa) on blots of 2-cell-embryo extract, one band (approx. 25.7 kDa) on morula extract, and one band (approx. 53 kDa) on blastocyst extract. The c-myc mAb did not react with any band corresponding to the c-myc protein on blots of extracts from unfertilized or fertilized ova, 2-cell embryos, 4-8-cell embryos, morulae, or blastocysts. These results suggest that some of the cross-reacting sperm antigens that are expressed during early cleavages, and the product of the c-myc proto-oncogene may have a role in normal early embryonic development.

Animals↗