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PubMed2004

The effect of vagal neural crest ablation on the chick embryo cloaca.

The cloaca, the caudal limit of the avian gastrointestinal tract, acts as a collecting chamber into which the gastrointestinal, urinary, and genital tracts discharge. It is intrinsically innervated by the enteric nervous system, which is derived from neural crest emigres that migrate from the vagal and sacral regions of the neural tube. Abnormal cloacal development can cause a number of anorectal anomalies, including persistent cloaca. Ablation of the vagal neural crest has previously been shown to result in an aganglionic hindgut to the extent of the colorectum. The aim of our study was to investigate the effect of vagal neural crest ablation on the cloaca, the limit of the hindgut in the developing chick embryo. Chick embryos were incubated until the 10-12 somite stage. The vagal neural tube corresponding to the level of somites 3-6 was then ablated, and eggs were incubated until harvested on embryonic day 11 (E11). Whole chick embryos were fixed, embedded in paraffin, and sectioned. Immunohistochemistry was then carried out using the HNK-1 monoclonal antibody to label neural crest cells, and results were assessed by light microscopy. Vagal neural crest ablation resulted in a dramatic decrease in the number of neural crest cells colonizing the chick embryo cloaca compared with control embryos. Ablated embryos contained only a small number of HNK-1-positive neural crest cells, which were scattered within the myenteric plexus in a disorganised pattern. Hypoganglionosis was also evident in other regions of the hindgut in ablated embryos. Ablation of the vagal neural crest results in a hypoganglionic cloaca in addition to hypoganglionosis of the hindgut. These results suggest that the cloaca is largely innervated by vagal neural crest emigres. Further studies involving quail-chick chimeras to investigate the exact contribution provided by both vagal and sacral neural crest cells to the cloaca should increase our understanding of the pathophysiology of conditions like persistent cloaca.

Animals↗

PubMed1975

[Study of the role of colicins in the formation of microbial association in experiments in chick embryos].

Experiments were conducted on chick embryos; conditions of formation of bacterial cenosis of Shigella sonnei and E. coli were reproduced. The role of colicinogenia in the formation of bacterial cenosis was demonstrated. An accumulation of colicines in high titres (1: 5120- 1:2560) in the chick embryonic cavity was noted in combined or separate cultivation of colicinogenic shigellae and E. coli. An intergenera transmission of the col-factor was traced in experiments on chick embryos. The data obtained served as foundation for recommendation of the accessible and economic model (chick embryos) for the in vivo study of colicinogenia of the enteric bacteria representatives.

Animals↗

PubMed1987

The ontogeny of the enzyme systems for the 5'- and 5-deiodination of thyroid hormones in chick embryo liver.

In the chick embryo liver, generation of T3 from T4 by 5'-deiodinating (5'D) systems is reported to be minimal until just before hatching, which occurs on day 21 of incubation. Studies were, therefore, performed to determine whether this is due to the absence of a 5'D system until late in development or to the presence of an active 5-deiodinating (5D) system capable of converting T4 to rT3 and T3 to 3,3'-diiodothyronine. Studies were performed in microsomes of liver from 15 to 21-day-old chick embryos. T3 was formed from T4 in microsomes from embryos at all stages studied provided that the substrate concentration was at least 5 X 10(-8) M. However, T4 could not be employed for studying changes in 5'D activity because the T3 formed underwent further degradation, and the T4 was also metabolized by 5D systems. rT3 was used instead, since its metabolism was less complex than that of T4, and Eadie-Hofstee plots of kinetic data were linear. Development was associated with a more than 2-fold increase in the maximum velocity of 5'D activity; there was no change in Km. 5D activity, which was studied using T3 as substrate, also exhibited linear reaction kinetics. 5D activity was highest on day 15 and decreased by more than 90% during the last 2 days of development due entirely to a decrease in the maximum velocity. Other characteristics of the two enzymes (substrate preference and inhibitor effects) indicate that they are comparable to the type I and III deiodinases found in mammalian systems. It is concluded that the failure to observe T3 generation from T4 in the developing chick until close to hatching, when substrate concentrations are below 5 X 10(-8) M, is due primarily to the presence of an active deiodinase which rapidly converts T4 and T3 to inactive analogs. It is suggested that the amount of T3 required by the developing embryo is extremely critical and the two enzyme systems act in a coordinated way to protect hepatic T3-sensitive mechanisms from overexposure to T3.

Age Factors↗

PubMed1991

Triiodothyronine stimulates and cyclic AMP inhibits transcription of the gene for malic enzyme in chick embryo hepatocytes in culture.

In chick embryo hepatocytes in culture, insulin and triiodothyronine (T3) increase malic enzyme activity and the abundance of malic enzyme mRNA by at least 50-fold, and glucagon or cAMP blocks this effect. Steps regulated by these hormones were defined by measuring transcriptional activity with the nuclear run-on assay and multiple fragments of the malic enzyme gene as probes. T3 alone caused a significant increase in transcription within 1 h, with a maximal increase of 30-40-fold occurring by 24 h. When T3 was added with insulin, 80% of the maximum rate was reached in 1 h. Insulin alone had no effect on transcription of the malic enzyme gene; it amplified the response to T3 in the first few hours after adding T3 but did not alter T3's maximal effect. Cyclic AMP for 1 h completely inhibited the increase in transcription caused by T3. The size and speed of the responses of the malic enzyme gene to T3 and cAMP suggest regulation of transcription initiation. T3-stimulated transcription of the malic enzyme gene did not require ongoing protein synthesis despite the fact that inhibitors of protein synthesis inhibited the T3-stimulated accumulation of its mRNA. T3 may directly activate transcription of this gene via its receptor. The pattern of DNase I hypersensitivity of the malic enzyme gene in chick embryo hepatocytes was the same as that in fed chick liver. Insulin, T3, and cAMP had no effect on that pattern. In chick embryo hepatocytes in culture, factors involved in regulation of transcription by insulin, T3, and cAMP may be bound to DNA independently of hormonal treatment.

Animals↗

PubMed2004

Development of a green fluorescent protein metastatic-cancer chick-embryo drug-screen model.

The chick-embryo model has been an important tool to study tumor growth, metastasis, and angiogenesis. However, an imageable model with a genetic fluorescent tag in the growing and spreading cancer cells that is stable over time has not been developed. We report here the development of such an imageable fluorescent chick-embryo metastatic cancer model with the use of green fluorescent protein (GFP). Lewis lung carcinoma cells, stably expressing GFP, were injected on the 12th day of incubation in the chick embryo. GFP-Lewis lung carcinoma metastases were visualized by fluorescence, after seven days additional incubation, in the brain, heart, and sternum of the developing chick embryo, with the most frequent site being the brain. The combination of streptokinase and gemcitabine was evaluated in this GFP metastatic model. Twelve-day-old chick embryos were injected intravenously with GFP-Lewis lung cancer cells, along with these two agents either alone or in combination. The streptokinase-gemcitabine combination inhibited metastases at all sites. The effective dose of gemcitabine was found to be 10 mg/kg and streptokinase 2000 IU per embryo. The data in this report suggest that this new stably fluorescent imageable metastatic-cancer chick-embryo model will enable rapid screening of new antimetastatic agents.

Animals↗

PubMed1994

Ontogeny of immunocytochemically demonstrable androgen- and androgen receptor-containing cells in the hypothalamus and adenohypophysis of the chick embryo.

Brain sections of male chick embryos, 6.5-18.5 days of age, were examined immunocytochemically for the presence of androgen- and androgen receptor-containing cells in the hypothalamus and adenohypophyseal pars distalis. Using antibodies (Ab) against both androgens (T-Ab) and the androgen receptor (AR-Ab), single- and double-immunostained cells were located in a total of five nuclei of the anterior-, mid-, and posterior-hypothalamus, as well as in the rostral and caudal lobes of the adenohypophyseal pars distalis. From Days 9.5-12.5, the mean number of androgen-immunostained cells within the hypothalamus and pars distalis increased significantly (P < 0.01), while from Days 12.5-18.5 there was no further statistically significant increase. The results of the present investigation support previous findings which suggest that in the chick embryo the negative feedback loop of the hypothalamo-adenohypophyseal-testicular (HATest) axis is functional by the 13th day of development (Woods et al., 1989a,b). They also agree with the observations of Wilson and Glick (1970) that in the male chick embryo testosterone organizes masculine mating behavior prior to Day 13.0.

Androgens↗

PubMed1983

Action of testis graft from puromycin- or cAMP-pretreated donor embryos on the regression of Müllerian ducts in the female chick embryo.

Female chick embryos grafted with a piece of embryonic testis manifest in a high percentage of cases a regression of their Müllerian ducts (MD) under the influence of a anti-Müllerian hormone (AMH) secreted by the graft. Puromycine or cAMP administered to grafted females reduced significantly the percentage of those presenting a MD regression. In the present work puromycin or cAMP was administered to the male graft-donor embryos and not to the grafted females as was done previously. A testis graft from a puromycin-pretreated donor was significantly less active on the MD than that from a normal embryo. It could be then concluded that puromycin acted at the level of the testis by inhibiting the AMH production. On the other hand, the treatment of donors with cAMP did not modify their testes with regard to their action on the grafted female MD. This showed that cAMP directly protected the MD against the AMH.

Animals↗

PubMed1964

GLUCOSE UTILIZATION BY CHICK EMBRYO HEART HOMOGENATES.

Homogenates of early chick embryos and homogenates of early chick embryonic hearts utilized the phosphogluconate pathway of glucose catabolism to a greater extent, relative to the glycolytic-Krebs cycle pathway, than did homogenates of hearts from older chick embryos or adult chicks. An abrupt drop in the relative participation by the phosphogluconate pathway in embryo heart homogenates occurs at about 5 to 7 days of incubation. Heart homogenates from adult chicks catabolize glucose almost entirely by the glycolytic-Krebs cycle pathway, with negligible participation by the phosphogluconate pathway.

Adenosine Triphosphate↗

PubMed1987

Formation of cartilage in organ-cultured leg buds of chick embryo.

When the leg buds from chick embryos at stages 17-23 were cultured as organ cultures in F12 medium, which contained chick serum and an extract of chick embryos, leg cartilage structures developed that included pelvic girdle, femur, tibiofibula, and tarsometatarsus. The proportion of explants with definite distal elements increased when the leg buds from later embryos were used. Supplementation with chick serum was essential. These results suggest that the pattern of formation of limbs in chick embryos can be studied in organ culture.

Animals↗

PubMed2006

Insulin stimulates proliferation but not 17beta-estradiol production in cultured chick embryo ovarian cells.

The development of the chick embryo gonads is influenced by gonadotropins [follicle-stimulating hormone (FSH), luteinizing hormone, human chorionic gonadotropin (hCG)]. We have previously shown that insulin enhanced the production of androgens in the testis of the newly hatched chicken and increased the proliferation of chick embryo testis cells. In the present paper, we have studied the effect of insulin on embryonic chick embryo ovarian cells and compared them with those of human FSH and hCG. The ovaries of 18-d-old chick embryos were dissociated and cultured for different periods in Dulbecco's modified Eagle's medium in the presence and absence of insulin, human FSH, hCG, and combinations of them. 3H-thymidine incorporation was used as an indicator of cell proliferation; steroids were measured by radioimmunoassay. Results showed that insulin enhanced the proliferation of ovarian cells in a dose- and time-dependent manner. Gonadotropins did not affect significantly the ovarian cell proliferation. Insulin did not change 17beta-estradiol production. The combination of insulin and FSH or insulin and hCG decreased the stimulation of estrogen secretion caused by the addition of the gonadotropins. In some experiments, ovarian cells were cultured with or without insulin, and subpopulations were identified. The results showed that insulin but not human FSH or hCG increased the proliferation of germinal cells after 60 h in culture. Insulin and human FSH did stimulate the other 2 subpopulations. In summary, present results suggest that insulin is an important hormone in the development of the chick embryo ovary.

Animals↗

PubMed1990

Activity of aldrinepoxidase, 7-ethoxycoumarin-O-deethylase and 7-ethoxyresorufin-O-deethylase during the development of chick embryos in ovo.

Since the chick embryo in ovo is susceptible to the action of some agents needing metabolic activation we studied the development of the activity of cytochrome P450-dependent monooxygenases in embryo/fetal tissue. The activities of aldrinepoxidase (AE), 7-ethoxycoumarin-O-deethylase (ECOD) and 7-ethoxyresorufin-O-deethylase (EROD) were measured in whole embryos, liver and yolk sac tissue of the chick embryo during development in ovo from day 4 to day 15 of incubation (DI). In yolk sac tissue enzyme activities could be detected from DI 4 on. While EROD activity was only marginally developed, AE and ECOD activities were more pronounced in the earlier developmental period and showed a clear decrease by the time the liver activities rose. With the methods used AE activity could be measured in the homogenate of the whole embryo proper from DI 4 on while EROD and ECOD activity was not detectable before DI 6 or DI 7, respectively. In liver tissue enzyme activities of the three monooxygenases studied developed to a considerable degree from DI 9 on and tended to exhibit maximum values around DI 11-13. Studies on monooxygenase activities in extra-embryonically located tissues have not been published until now. The importance of the yolk sac as a metabolically relevant organ during embryogenesis is pointed out in this study.

7-Alkoxycoumarin O-Dealkylase↗

PubMed1984

Alcohol dehydrogenase activity in the developing chick embryo.

Before day 9 of incubation, chick embryos contain no measurable alcohol dehydrogenase (ADH) activity. Following day 9 of incubation, chick embryo liver ADH activity increases as a linear function of liver mass. A single dose of ethanol given at the start of incubation is cleared only slowly prior to day 9 of incubation but is completely cleared by day 13. Chick embryo liver ADH has two detectable isozymes throughout development. The percentage contribution of each isozyme to total ADH activity does not change significantly during development. The Km apparent of chick liver ADH is significantly increased shortly after hatching relative to the Km apparent of embryonic ADH. Ethanol exposure during incubation has no effect on the development of ADH activity or isozyme distribution.

Alcohol Oxidoreductases↗

PubMed1992

Physical properties, lipid composition and enzyme activities of hepatic subcellular membranes from chick embryo after ethanol treatment.

Exposure of chick embryos to ethanol resulted in significant alterations to the lipid composition of various different hepatic subcellular membranes. A marked decrease in cholesterol levels and an increase in the phospholipid content of microsomes and mitochondria was observed. Ethanol also affected the fatty acid profiles, mainly by decreasing the percentage of oleic acid in phosphatidylcholine and phosphatidylethanolamine in the mitochondria and phosphatidylethanolamine in the microsomes. In spite of these changes ethanol only induced alterations in the fluidity of the mitochondrial membranes, which showed a more rigid core, in contrast to the phospholipid-head region, which was not affected. In accordance with the changes observed in the physical state of the membrane, the enzymes involved in the microsomal electron-transport systems were not modified by ethanol, while cytochrome oxidase activity decreased by 50% compared to the activity in the mitochondria from control chick embryos. These findings establish that during the chick-embryo developmental period the mitochondria are more sensitive to ethanol than are the microsomes.

Animals↗

PubMed1978

The development of chick spinal cord in tissue culture. II. Cultures of whole chick embryos.

By using whole-chick-embryo cultures followed by fragment cultures of spinal-cord primordia, it was possible to reproduce in vitro the whole process of neuronal development beginning with its initiation and continuing up to and including the maturation of neurons. Normal whole embryos were developed to Hamilton-Hamburger stages 17 and 18 by growing embryos from the primitive streak stage on large (28-mm) glass rings. The advantage of whole-embryo cultures is that development can be staged accurately, which is especially important during the early stages when morphogenesis progresses very rapidly. By using such accurately staged embryos and tritiated thymidine, we have determined that some postmitotic neuronal precursor cells appear in chick embryos as early as Hamburger-Hamilton stages 4 and 5, i.e. the definitive streak stages before the neural tube has formed.

Animals↗

PubMed1982

[Cultivation of various avian viruses in pheasant trachea organ cultures and chick embryos].

Stationary tracheal organ cultures of pheasants and chick embryos, treated with a mucolytic agent were used to study the ciliostatic effect of the following viruses: fowl pest (FPV), Newcastle disease (NDV), infections laryngotracheitis (ILV), and infections bronchitis (IBV) - strain Beaudette. In chick embryo tracheal cultures ciliostasis was found to set in as follows: for FPV - at the 24th hour; for NDV - at the 72nd-120th hour; for ILV - at the 168-192nd hour; and for IBV-at the 72nd-96th hour. The ciliostatic effect produced by NDV and IBV coincided in terms of time and dynamics. In pheasant tracheal organ cultures ciliostasis set in as follows: for FPV - at the 24th hour; for NDV - at the 72nd-120th hour; and for ILV - at the 168-192nd hour. This system was shown to be unsusceptible to IBV which produced no effect whatever. In mixed organic cultures, containing several tracheal segments of pheasants and chick embryos each per petri dish IBV did bring about ciliostasis in the chick embryo segments only, within the period after inoculation as cited above. It is stated that pheasant tracheal organ cultures could be employed in the case of an express initial differentiation of FPV, NDV, and ILV, recording the time period for the setting in of full ciliostasis following the inoculation of the respective viruses. Discussed is the possibility of identifying IBV, using mixed tracheal organ cultures of pheasants and chick embryos.

Animals↗

PubMed1991

Absence of O6-alkylguanine-DNA alkyltransferase induction in chick embryo liver and brain following X-irradiation or treatment with bleomycin.

1. The presence of O6-alkylguanine-DNA alkyltransferase (AT) in liver and brain of chick embryos, chicks and hens was demonstrated. An induction of AT activity has only been found in the liver of chicks and hens 48 hr after X-irradiation (5, 10 or 12 Gy). 2. The administration of methylmethanesulphonate to the chick embryo resulted 3-24 hr later in strong inhibition of AT activity accompanied by DNA alkylation. Under the same conditions, X-irradiation, dimethylnitrosamine and bleomycin exhibited no effect. 3. The results are compared with those obtained in mouse, rat and human foetal tissues.

Animals↗

PubMed1991

Presence of embryotoxic factor in the sera of neonates affected by myelomeningocele: a study on chick embryo.

An experimental study on chick embryos was conducted where 0.02 mL of serum, taken from five neonates (1 to 7 days of age) with myelomeningocele was injected separately into the fertile white leghorn eggs, at zero hour of incubation. A total of 150 experimental and 135 control eggs were injected. It was observed that the embryos of chick exposed to experimental serum had an increased frequency of embryonic death and/or gross abnormalities as compared with the control group (chi 2 = 32.07; P less than .001). The anomalies observed were those of neural tube, gastrointestinal system, and musculoskeletal system. In addition, there was a generalized growth retardation among experimental embryos. These malformations are probably due to an embryotoxic factor, which is present in the serum of the baby with myelomeningocele and has been transmitted transplacentally.

Animals↗

PubMed1975

Specific increase in polyamine levels in chick embryo cells transformed by Rous sarcoma virus.

Chick embryo fibroblasts and chorioallantoic membranes of chick embryos infected with oncogenic or nononcogenic viruses were analyzed for polyamines. Nononcogenic viruses (influenze, Newcastle disease, or vaccinia virus) had no effect on the polyamine content of chorioallantoic membranes. Transformation of chorioallantoic membranes by a wild-type or temperature-sensitive mutant strain of Rous sarcoma virus under permissive conditions (37 degrees) caused a 2- to 4-fold increase in cellular spermidine and putrescine content. Only putrescine accumulated in chick embryo fibroblasts transformed by Rous sarcoma virus at 37 degrees. At the nonpermissive temperature (42 degrees), the temperature-sensitive mutant, unlike the wild-type strain, did not alter cellular morphology or polyamine content.

Allantois↗