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PubMed1980

The effect of triamcinolone on the development of the bursa of Fabricius in chick embryos.

Triamcinolone acetonide (TAC), a long-acting synthetic glucocorticoid, markedly reduces survival rates in chick embryos when injected in small (10--100 ng) single-injection doses on days 5 or 9 of incubation. In addition to its embryotoxic effect, TAC causes such gross malformations as gastroschisis, reduced body weight, encephalocele, micrognathia, curled toes, and club feathers. These effects of TAC are more severe in 5-day-old chick embryos than in 9-day-old ones. A comparison with cortisol (hydrocortisone), a structurally similar, naturally occurring steroid, indicates that TAC is approximately 600 times more toxic in chick embryos than cortisol. TAC also inhibits differentiation of the bursa of Fabricius: single injections on the chorioallantoic membrane (CAM) of 10--20 ng on day 5 or 9 reduced size and weight of this lymphoid organ. Histological examination showed a sharp reduction in the size and number of bursal follicles, a reduction in the number of lymphocytes within these follicles, and a degeneration of the epithelium covering bursal plicae.

Animals↗

PubMed1977

Lipoperoxide level of the retina of chick embryo exposed to high concentration of oxygen.

To approach the mechanism of degeneration of the retina in retinopathy of prematurity, a model experiment using chick embryo was carried out. Upon exposing chick embryo at various stages to a high concentration of oxygen at 2 atm pressure, lipoperoxide levels of both the blood and the retina were elevated. The change in lipoperoxide level of the liver was not significant, except for a slight increase at the 9th day of incubation. Upon exposing chick embryo of the 14th day to high concentration of oxygen at ambient pressure, lipoperoxide levels of both the blood and the retina were elevated at 6 h and 12 h of exposure, but significant change was not observed in the lipoperoxide level of the liver.

Animals↗

PubMed1980

On the effect of inhibitors of mitochondrial macromolecular-synthesizing systems and respiration on the growth of cultured chick embryo cells.

We have found that chick embryo fibroblasts (DEF) cultivated in the presence of tryptose phosphate broth (TPB) are inherently resistant to the growth inhibitory effect of ethidium bromide (EB). As demonstrated by cytochrome oxidase activity and oxygen consumption measurements, analyses of reduced-minus-oxidized cytochrome spectra and electron microscopic observations, TPB did not seem to prevent the inhibitory effect of EB on mitochondrial DNA transcription. EB-treated chick cell populations cultivated in the presence of TPB behave essentially the same as populations treated with chloramphenicol (CAM) and grow with mitochondria devoid of a functional respiratory chain. In contrast to CAM-treated CEF populations, however, the respiratory activity of EB-treated cell populations did not reappear when the cells were shifted back to EB-free medium. Attempts to demonstrate that TPB confers resistance to the growth inhibitory effect of carbomycin and mikamycin, inhibitors of the mitochondrial protein-synthesizing system, have failed, the drugs being cytotoxic at doses where protein synthesis on mitoribosomes is not suppressed. On the other hand, the present results demonstrated that chick cell populations proliferate in the presence of the respiratory inhibitors rotenone, antimycin A, amytal and oligomycin whether or not TPB is present in the growth medium.

Amobarbital↗

PubMed1984

Intercellular relationships during cavitation of aggregates of extraembryonic endoderm cells from gastrulating chick embryos.

Extraembryonic endoderm cells from gastrulating chick embryos undergo epiboly and change from a multilayered cell group to a single cell layer surrounding the yolk. Single cell suspensions from this cell layer can aggregate in vitro to form aggregates that cavitate. To study the stages of cavitation aggregates were harvested after different times in culture, and fixed and processed for light and electron microscopy. In aggregates harvested at 75 min of culture cell contact consisted of areas of parallel and close membrane apposition and interdigitation. Desmosomes were occasionally observed. Aggregates in the early stages of cavitation (24 h) contained numerous intercellular spaces bordered by irregularly shaped cells which appeared to be digesting their yolk and releasing material extracellularly. Long cytoplasmic projections were extended into these spaces. In addition to regions of parallel membrane apposition and interdigitation, desmosomes and adherens junctions were observed. Cells closer to the periphery of the aggregates displayed fewer cell projections and also showed signs of release of material extracellularly. After 48 h of culture, a single smooth-walled central cavity was present and cells still exhibited signs of extracellular release of material. These same cell shapes and intercellular junctions were also observed when area opaca tissue dissected from gastrulating embryos was examined. Aggregates of different sizes were created and cultured. The results suggest that a critical tissue mass may be important for cavitation.

Animals↗

PubMedDate not supplied

Teratogenic and antiteratogenic effects of nicotinamide derivatives in chick embryos.

Teratogenic and antiteratogenic effects of nine nicotinamide analogs in chick embryos were investigated. Further, the teratisms of 6-aminonicotinamide (6-AN), nicotinamide analogs, and an organophosphate (diazinon) were compared. White leghorn chick embryos were used. Agents were injected into the yolk of eggs on d 3 of incubation. Morphological observations were made on d 17 of incubation. Chemical names for compounds I to IX are: I, 6-dimethylaminonicotinamide; II, 6-diethylaminonicotinamide; III, 6-methylamino-3-(N-methyl)-nicotinamide; IV, 6-dimethylamino-3-pyrimidine carboximide; V, 6-(dimethylamino)-nicotinic acid; VI, 6-chloro-3-[N-(5-diethylamino)-2-pentyl]-nicotinamide; VII, 6-mercaptonicotinamide; VIII, [N-acetyl-N'-(3-pyridyl)-carbonyl]-hydrazine; IX, nicotinamide 1-N-oxide. The LD50 values in mumol per egg were as follows: 6-AN, 0.073; compound II, 0.23; compound III, 1.11; compound I, 1.32; compound VI, about 3. Compounds IV, V, VII, VIII, and IX showed no toxicity or lethality at the highest doses tested (10 mumol/egg). Among the nine nicotinamide analogs, compounds I, II, and III, which have an amino group at the 6-position of the pyridine ring, were teratogenic. Their teratogenic signs were similar to those caused by 6-AN: they showed growth retardation, anteriorly directed short legs, and coarse, dense feathering. The teratogenic effects of compounds I, II, and III were prevented by pretreatment with nicotinamide, as were the effects of 6-AN and diazinon. Among the nine analogs, only compound VIII had an antiteratogenic effect against the diazinon-induced micromelia (in which the cardinal signs were tibiotarsal angulations and poor feathering). For teratisms produced by 6-aminonicotinamide analogs and organophosphates, nicotinamide was an effective antiteratogenic agent. However, some differences in the malformations induced by both types of agents were found. We suggest that the addition of a 3-acetylpyridine type to the nicotinamide-related teratisms (6-AN type, 3-acetylpyridine type, and organophosphate type) will provide a clearer distinction among the types.

Animals↗

PubMed1988

Myopathy and encephalopathy in chick embryos experimentally infected with Akabane virus.

Chick embryos infected with Akabane virus by the yolk sac route at 6 days of incubation developed polymyositis and encephalitis. At 3 to 7 days after inoculation, skeletal muscles had myotubule degeneration, clumping of muscle cell nuclei, and infiltration of heterophils; dysplasia and aplasia were evident at 9 to 15 days after inoculation. Changes in the cerebral neostriatum and optic lobes at 2 to 11 days after inoculation included necrosis of primordial nervous tissue, hemorrhages, and hyperplasia of the vascular endothelial cells. Cavities were in nervous tissue subsequent to encephalitis. Hydranencephaly and vascular wall thickening were found 13 and 15 days after inoculation. Embryos infected intravenously at 15 days incubation had foci of encephalitis 3 to 6 days after inoculation, including neuronal degeneration, neuroglial hyperplasia, vascular endothelial proliferation, and heterophil infiltration.

Anencephaly↗

PubMed1984

Correlation between changes in cell adhesion and the ratio of N- to O-linked glycopeptides during chick embryo development.

After treatment with trypsin, chick embryo fibroblasts exhibited an age-related difference in their capacity to readhere to the substratum, since 8-day-cells readhered more rapidly than 16-day-cells. Treatment with tunicamycin altered embryo cell readhesion to the substratum in varying degrees, depending on the duration of drug treatment and of readhesion assay. The effect of tunicamycin was not toxic and was totally reversible with time after its removal. These results indicated that embryo cell readhesion involved trypsin-sensitive cell surface glycoproteins. During embryo development, the glycosylation of cell surface glycoproteins altered markedly. The ratio of N-linked to O-linked glycan chains dropped from 80/20 in 8-day-cells to 55/45 in 16-day-cells, indicating that the relative labelling of O-linked glycan chains increased during embryo development. This result was confirmed by alkaline treatment of radiolabelled glycan chains, and by the fact that tunicamycin treatment reduced 14C-glucosamine incorporation by greater than or equal to 80% in 8-day-cells but only 60% in 16-day-cells. Marked changes were observed during embryo development in the structure of the N-linked glycan chains; concanavalin A-Sepharose chromatography showed that these changes concerned the glycopeptides containing complex type carbohydrate chains. The ratio of tri- plus tetra-antennary chains to bi-antennary chains increased about 2.5-fold between the 8th and 16th day of development. A correlation was noted between embryo cell readhesion to the substratum and N-glycosylation of cell surface glycoproteins. The N-linked glycoconjugates played a crucial part in cell readhesion. The possible role of O-linked structures in such readhesion is discussed.

Animals↗

PubMed1995

Action of testosterone on the estradiol-induced feminization of the male chick embryo.

The early treatment of male chick embryos with estradiol induces the feminization of their sex tract, i.e. both their gonads and müllerian tract exhibit female features. The additional treatment of estrogenized male embryos with testosterone propionate antagonizes the effects of estradiol on both gonads and müllerian ducts. Our data give further support to the view that testosterone and estrogens act respectively as agonist and antagonist modulators of the secretion of the anti-müllerian hormone.

Androgen-Insensitivity Syndrome↗

PubMed1977

[Interkinetic nuclear migration in nasal placode of chick embryo].

Cells of nasal placode of chick embryos were studied with thymidine H3 and autoradiography. Our results shown, that the nuclei in the nasal placode synthesize DNA in the outer zone, then migrate toward the inner zone to undergo division and subsequently return to the outer zone.

Animals↗

PubMed1993

Early development of the chick embryo.

The ultrastructure of the early chick embryo was investigated, using scanning (SEM) and transmission electron microscopy (TEM). Eggs were obtained from the shell gland by injecting hens intravenously with a synthetic prostaglandin or arginine vasopressin. Embryos were examined during late cleavage (stages IV-VI, Eyal-Giladi and Kochav, '76), formation of the area pellucida (stages VII-XI), and formation of the hypoblast (stages X-XIV). SEM highlighted the reduction in cell number at the underside of the embryo during formation of the area pellucida although it became apparent that the thickness of the embryo is not reduced to a single layer of cells at stage X. In addition, blastomeres at the perimeter of embryos (stages V-VI) project filopodial extensions onto a smooth membrane that separates the sub-embryonic cavity from the yolk. During hypoblast formation, epiblast cells generate stellate projections at their basal aspect, thus providing a meshwork for the advancing secondary hypoblast cells. By stage XII the epiblast was one cell thick and reminiscent of a columnar epithelium when viewed transversely. Cells of the deep portion of the posterior marginal zone were distinguished morphologically in the stage XII embryo by their many cell surface projections and ruffled appearance. Blastomeres at the perimeter of stage V-VI embryos projected filopodial extensions onto a smooth membrane which separates the sub-embryonic cavity from the yolk. This membrane is presumed to be confluent with the cytolemma. Evidence is presented demonstrating the presence of intracellular membrane-bound droplets which are hypothesised to contain sub-embryonic fluid.

Animals↗

PubMed1977

Effects of N2, O2'-dibutyril cyclic GMP on the nucleoside phosphotransferase activity of the retina of the chick embryos.

In the retina of the chick embryo, 2 different forms of nucleoside phosphotransferase take part in the phosphorylation of thymidine. One is an unstable form with higher molecular weight. The other with lower m. wt is a stable form. This paper shows that N2,O2'-dibutyril cyclic GMP causes a marked decrement of the activity of the unstable nucleoside phosphotransferase.

Animals↗

PubMed1980

[Comparison of the effects of concanavalin A on cell growth and the transport of 3-O-methylglucose in chick embryo fibroblasts].

The proliferative capacity of Chick embryo fibroblasts was modified by Con A treatment. Con A decreased the growth of fibroblasts from young embryos (8 days), whereas the lectin stimulated the growth of fibroblasts from older embryos (16 days). This differential effect of Con A did not result from changes in cellular permeability to thymidine, but rather from Con A induced modifications of hexose transport. Changes in hexose transport would cause, as a response, parallel modifications in glycolysis and hence energy charge, which would alter proliferative capacity.

3-O-Methylglucose↗

PubMed1978

Studies on the cytodifferentiation of the neuroblasts and visual cells in the chick embryo retina, using the electron-microscopic autoradiography of 3H-thymidine.

Studies on the histogenetic analysis of cytodifferentiation of the neuroblast and visual cell in the chick embryo retina were made using the autoradiography of 3H-thymidine. The posterior pole region of the eyeball was observed in all the animals used. The retina in a 4-day-old chick embryo consists exclusively of matrix cells forming the matrix layer. In a 5-day-old chick embryo retina, neuroblasts first differentiated from the matrix cells migrate into the outer part of the matrix layer, forming mantle layer. The matrix cell is a homogeneous epithelial cell containing abundant free ribosomes and a poorly developed cytoplasmic membrane system in the cytoplasm. The characteristic sign of differentiation of the neuroblast is an appearance of elements of rough-surfaced endoplasmic reticulum and an indentation of the nucleus. The primitive visual cell having just lost its ability to synthesize DNA appears just beneath the pigment epithelium in a 7-day-old chick embryo, and all the cells lying beneath the pigment epithelium lose the ability to synthesize DNA at 10 days of incubation. The cytoplasmic process of the matrix cell is in contact with the adjacent one, making an apicolateral junction. When the matrix cell loses its ability to synthesize DNA, a big tentlike process extending over the level of the apicolateral junction appears. This phenomenon is considered to be a sign of differentiation from matrix cell to primitive visual cell, and this big tentlike process containing 2 centrioles is a primordium of the inner segment of the visual cell.

Animals↗

PubMed2001

Effects of cadmium on formation of the ventral body wall in chick embryos and their prevention by zinc pretreatment.

BACKGROUND: Cadmium (Cd) is an established experimental teratogen whose effects can be reversed by pretreatment with zinc. Mesodermal development is a frequently reported target for Cd teratogenicity. The aim of this study was to examine the mechanisms of Cd induced body wall defects in chick embryos. METHODS: Chick embryos in shell-less culture were treated with 50 microl of cadmium acetate (8.9 x 10(-5) M Cd(2+)) at 60-hr incubation (H.-H. stages 16-17). Controls received equimolar sodium acetate. Other embryos were treated with various concentrations of zinc acetate and then with Cd or NaAc 1 hrs later. Development was evaluated 48 hrs later. Resin-embedded 1-microm sections were examined at earlier stages. RESULTS: Cd caused embryolethality (35%), ventral body wall defect with malpositioned lower limbs (40%), and weight reduction in survivors. After 4-hr treatment with Cd, breakdown of junctions between peridermal cells with rounding up and desquamation occurred. Shape changes were also seen in the basal layer of the ectoderm. At 4 hr, cell death was evident in lateral plate mesoderm, somites, and neuroepithelium; the lateral plate mesoderm began to grow dorsally, carrying the attached limb buds with it. Zn pretreatment protected against the lethal, teratogenic, and growth-retarding effects of Cd, as well as ectodermal changes and cell death. CONCLUSIONS: Cd disrupts peridermal cell adhesion and induces cell death in the mesoderm. This may result in abnormal growth of lateral plate mesoderm and in a body wall defect. Zn pretreatment prevents both the gross teratogenic effects and the cellular changes, most likely by competition with Cd.

Abnormalities, Drug-Induced↗

PubMed1975

Estrogen target sites in the brain of the chick embryo.

Autoradiograms prepared from brains of chick embryos after injection of [3H]estradiol demonstrate the existence of target cells for estrogen in the medial preoptic and ventral hypothalamic regions as early as day 10 of incubation. Target cells also appear in telencephalic locations during later stages of embryonic development. These hormone-concentrating cells probably are the anatomical substrate for the formative action of sex steroids during embryonic life on certain brain functions such as control of sexual and aggressive behaviour and gonadotropin secretion.

Age Factors↗

PubMed1984

Biosynthesis of gangliosides in cultured retina from chick embryos.

Retina tissue from 7-day chick embryos was maintained in culture for up to 10 days. After 5 days in culture the incorporation of [3H]leucine into proteins and of [3H]glucosamine into gangliosides was similar to that found in retinas from 12-day embryos. The incorporation of [3H]thymidine into DNA decreased steadily with time in culture; after 5 days it was about 20% of the initial value and approximately twice that determined in retinas from 12-day embryos. The radioactivity pattern of gangliosides labeled with [3H]glucosamine showed a predominance of the label in disialosyllactosylceramide (GD3); up to the 3rd day of culture. From then on, there was a progressive increase in the labeling of disialosylgangliotetraosylceramide (GD1a); by day 7 of culture, labeling of GD1a predominated and the labeling pattern was indistinguishable from that found in retinas from 12-day-old embryos. The specific activities of the CMP-NeuAc:GM3 sialosyl- and UDP-GalNAc:GM3 N-acetylgalactosaminyl-transferases decreased to 15% and increased to 400%, respectively, of the values determined in the retinas of 7-day embryos. The cultured retinas progressed in their organization into layers with culture time. The labeling transition from GD3 to GD1a was also detected after inhibition of the histotypic organization by addition of 5-bromo 2-deoxyuridine to the culture medium. Results suggest that high activity of GM3:sialosyl transferase and high labeling of GD3 are associated with the proliferative state of retina cells, while high activity of GM3:N-acetylgalactosaminyltransferase and high labeling of GD1a are associated with the non-proliferative, differentiated state of these cells.

Animals↗

PubMed1996

Distribution of blood flow between embryo and vitelline bed in the stage 18, 21 and 24 chick embryo.

OBJECTIVE: We defined the distribution of blood flow between the embryo and the extraembryonic vascular bed as an initial step in understanding the control of flow distribution in the early developing heart. METHODS: Dorsal aortic blood flow of stage 18, 21, and 24 chick embryo (n > or = 7 at each stage) was measured with a 20 MHz pulsed-Doppler velocity meter. Analog waveforms were digitally sampled at 500 Hz. 1-5 x 10(3) yellow microspheres in saline suspension were injected into the vitelline vein. The embryo and the extraembryonic vascular bed were harvested and separated from each other. The dye on the microspheres from each portion was extracted and extrapolated from the standard curve of the absorbance of dye concentrations per number of microspheres quantified by spectrophotometry. Blood flow was calculated from the integral of blood velocity and aortic cross-sectional area multiplied by the fraction distribution of microspheres in the embryo and extraembryonic vascular bed. Data were presented as mean +/- standard error of the mean. RESULTS: The proportion distribution of microspheres between embryo and extraembryonic vascular bed shifted from 18.7 +/- 2.5 vs. 81.3 +/- 2.5% at stage 18, 25.1 +/- 3.0 vs. 74.9 +/- 3.0% at stage 21, and 34.2 +/- 2.4 vs. 65.8 +/- 2.4% at stage 24. Indices of blood flow normalized to wet weight (mean +/- 95% confidence interval) were similar between the embryo and the extraembryonic vascular bed, but increased throughout the stages. CONCLUSION: During embryogenesis, blood flow per unit mass is evenly distributed between the metabolically active embryo and the extraembryonic vascular bed.

Animals↗

PubMed1978

Molecular properties of a major cell surface protein from chick embryo fibroblasts.

The molecular structure of chick embryo fibroblast cell surface protein has been investigated by ultracentrifugation, circular dichroism, and fluorescence. Most measurements were restricted to alkaline solutions because of the limited solubility of this protein at more neutral pH values. A very high frictional ratio for the protein suggests an asymmetric structure. However, there are elements of organized structure since typical thermal transition curves were found by several methods. Consequently, a model in which ordered domains are connected by flexible polypeptide chains seems to account for all the hydrodynamic and optical data.

Animals↗