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PubMed1981

Development of opiate tolerance in the chick embryo.

Tolerance to morphine was produced in the chick embryo. Eggs were injected with morphine sulfate (MS) (20 mg/kg egg) or H2O daily starting on incubation day 12. On day 16, embryo activities were recorded and eggs were injected with either MS or naloxone. Activity of H2O-pretreated controls decreased after both MS and naloxone. Embryos treated with MS from incubation days 12-15 showed no activity change after morphine and responded to naloxone with increases in activity. Baseline rates of distress vocalizations (DV) of 1-2 day old chicks were not affected by MS pretreatment during incubation days 12-19. However, 1 mg/kg MS decreased the rate of DV of control chicks by 90% whereas MS-pretreated chicks were unaffected. At age 4-5 days, the baseline rate of DV and rate after MS were higher in MS-pretreated chicks. However, all chicks showed significant decreases in rate of DV after MS injection. Naloxone increased the rate of DV of paired 1-2 day old chicks, but response of MS-pretreated chicks was significantly greater than controls.

Animals↗
PubMed1984

Correlation between mixed-function oxidase enzyme induction and aflatoxin B1-induced unscheduled DNA synthesis in the chick embryo, in vivo.

The unscheduled DNA synthesis (UDS) technique has been adapted for use in the chick embryo, in vivo, to determine the relationship between induction of the mixed-function oxidase (MFO) enzyme system and genetic damage from an indirect-acting mutagen-carcinogen. Embryos were injected at 6 days of incubation (DI) with either phenobarbital (PB), a specific inducer of P-450-associated enzyme activities, or 3,4,3',4'-tetrachlorobiphenyl (TCB), a specific inducer of P1-450-associated enzyme activities. Aflatoxin B1 (AFB1) was injected 24 hr later (7 DI), followed by a 5-hr continuous 3H-thymidine exposure. The livers were removed, prepared for autoradiography, and hepatocytes were scored for an increase in grains/nucleus, indicative of UDS. Aflatoxin B1 caused a dose-related increase in UDS in all control and induction groups. Phenobarbital-induced embryos had an increased UDS response while TCB-induced embryos had a decreased UDS response, relative to noninduced embryos, for each dosage of AFB1. This suggests that the genotoxicity of an indirect-acting mutagen-carcinogen can be either increased or decreased, in vivo, depending on the inducer used. The chick embryo provides an excellent system for studying the effect of MFO induction on the genotoxicity of promutagen-carcinogens in a developing system.

Aflatoxin B1↗
PubMed1964

PLAQUE ASSAY FOR PSITTACOSIS VIRUS IN MONOLAYERS OF CHICK EMBRYO FIBROBLASTS.

Piraino, F. (City of Milwaukee Health Department, Milwaukee, Wis.), and C. Abel. Plaque assay for psittacosis virus in monolayers of chick embryo fibroblasts. J. Bacteriol. 87:1503-1511. 1964.-A tissue culture system for the assay of 6BC psittacosis virus by plaque production on chick embryo fibroblast cells is described. Experiments are given which characterize the specificity of the reaction and identify factors found to cause variations in plaque counts. The statistical data obtained indicate this assay to be a precise and highly reliable procedure for the detection of 6BC virus and antibody.

Antibodies↗
PubMed1964

EFFECT OF 6-AMINONICOTINAMIDE ON CHICK-EMBRYO TISSUE CULTURES INFECTED WITH VACCINIA VIRUS.

Lee, Spencer H. S. (Dalhousie University, Halifax, Nova Scotia). Effect of 6-aminonicotinamide on chick-embryo tissue cultures infected with vaccinia virus. J. Bacteriol. 88:885-892. 1964.-6-Aminonicotinamide (6-AN) was shown to render chick-embryo fibroblast (CEF) tissue cultures refractory to infection with vaccinia virus. Pretreatment of CEF cultures for 8 hr at 36 C with 5 mug/ml of 6-AN prior to addition of vaccinia virus reduced the titer of active virus to about 0.4% of the levels obtained in the untreated controls, when measured by the number of plaque-forming units per milliliter. The addition of 5 mug of 6-AN to CEF cultures before virus infection retarded the progress of vaccinial infection by 8 to 10 hr at 36 C. The inhibitory effect caused by 5 mug/ml of 6-AN could be reversed by the simultaneous addition of 5 to 50 mug/ml of nicotinamide, but not if added at a later time. 6-AN appears to act on the host cell and not on vaccinia virus. For these tests, a simple plaque assay method was devised, by use of a fluid overlay technique with screw-capped tubes (16 by 125 mm) containing CEF cultures.

6-Aminonicotinamide↗
PubMed2005

Effects of cadmium on cell death and cell proliferation in chick embryos.

The aim of this study was to examine cell death and cell proliferation in chick embryos destined to have ventral body wall defects as a result of cadmium (Cd) treatment. Embryos in shell-less culture were treated with 50 microL Cd acetate (8.9x10(-5)M Cd2+) at Hamilton-Hamburger (H.-H.) stage 16-17, or with equimolar sodium acetate. TdT-Mediated dUTP nick end labelling (TUNEL) showed the mode of cell death to be apoptosis commencing 4 h after treatment in somites and neural tube. Desquamation also occurred in the peridermal layer of the ectoderm. Cd caused no changes in the S-phase population of any tissue except ectoderm. The peridermal layer of the latter had a 40% reduction in labeling index (LI) 5.25 h after treatment but increased thereafter, being 30% greater than control values at 25.25 h. The occurrence of gross malformation was strongly correlated with the degree of apoptosis and in turn with the extent of peridermal desquamation. Pre-treatment with zinc acetate (10x the dose of Cd) prevented gross malformation, apoptosis and the effect of Cd on peridermal proliferation. We hypothesize that the ventral body wall defect resulting from Cd treatment in chick embryos is the result of changes in the somites perhaps following interruption of a signalling pathway originating in ectoderm.

Acetates↗
PubMed1988

Aldosterone nuclear receptors in kidneys of chick embryo.

We have studied the properties of the nuclear receptors for aldosterone in kidneys of chick embryo. Aliquots of 0.4 M KCl nuclear extracts were incubated with [3H]aldosterone with or without 1 microM RU28362, a potent glucocorticoid analog. Scatchard analyses of binding data revealed two classes of binding sites with Ka of 0.26 and 0.03 X 10(9) M-1 and Nmax of 330 fmol and 620 fmol/mg DNA respectively. In presence of RU28362, however, we observed only a single class of binding sites with a Ka of 1.02 X 10(8) M-1 and a Nmax of 90 fmol/mg DNA. Competition studies performed in presence of RU28362 showed that aldosterone was the more effective competitor followed by corticosterone, progesterone, deoxycorticosterone, dexamethasone, cortisol, triamcinolone acetonide and cortisone. The nuclear complexes had a sedimentation coefficient in the area of 8 S which changed to 4-5 S in the presence of 0.4 M KCl. This effect of KCl was prevented by the addition of 10 mM sodium molybdate. Always in the presence of the glucocorticoid analog, by DEAE-c chromatography we observed a major specific aldosterone-binding fraction which was eluted with 0.2 M KCl. This fraction sedimented at 8.4 S in the absence of sodium molybdate and KCl. In the absence of RU28362, DNA-c columns retained only a small portion of the nuclear complexes which were eluted with KCl. These complexes sedimented, on sucrose gradient, at 4.6 and 3.1 S, whereas those which did not bind to DNA-c had a sedimentation coefficient of 8 S. In the presence of RU28362, the majority of bound [3H]aldosterone remained in the column flow-through fraction; when this fraction was further analyzed on DEAE-c, complexes were eluted with 0.2 and 0.3 M KCl. These data indicate that nuclear receptors for aldosterone are present in small number in kidneys of chick embryo and that they are mostly in the 8 S form.

Aldosterone↗
PubMed1990

Cardioteratogenic dose of ethanol in the chick embryo results in egg white concentrations comparable to human blood alcohol levels.

Three-day-old chick embryos were exposed to a dose of ethyl alcohol (0.32 ml of 50% ethanol) that we previously demonstrated produces cardiac malformations in 96.6% of the animals. Ethanol was administered into the air sac at 72-80 h of incubation. Samples of egg white were drawn at 2, 6 and 24 h after treatment and analyzed by capillary gas-liquid chromatography. Ethanol concentrations were significantly higher at 6 and 24 h after exposure than at 2 h (P less than 0.01), but there were no differences in mean concentrations between 6 and 24 h (P greater than 0.2). Furthermore, concentrations (43-303 mg dl-1) were comparable to human blood alcohol levels during intoxication. These results suggest that the cardioteratogenic doses of ethanol administered to chick embryos in a previous study are not excessive in terms of potential human embryo exposure.

Animals↗
PubMed1981

[Changes in the female gonads of the chick embryo after tamoxifen].

Tamoxifen has been given to Chick embryos between the 3rd and 7th day at doses of 0.2-2 mg/egg. It was non-toxic and strongly anti-estrogenic. The female gonads were modified in their development. The ovary showed dense medulla with numerous cords and a reduced cortex. The right gonad partially regressed and was "masculinized". Mullerian ducts normally regressed in tamoxifen-treated male embryos. These results suggest the physiological intervention of estrogen during the normal embryonic female development.

Animals↗
PubMed2000

Down-regulation of the extracellular matrix protein SPARC in vSrc- and vJun-transformed chick embryo fibroblasts contributes to tumor formation in vivo.

In vitro transformation of primary cultures of chick embryo fibroblasts by the membrane-bound vSrc or the nuclear vJun oncoproteins is correlated with a down-regulation of the secreted glycoprotein SPARC (also called BM-40 or osteonectin). This protein is a nonstructural component of the extracellular matrix that is thought to regulate cell-matrix interaction during development, wound repair, and carcinogenesis. Its precise function remains unclear. To estimate the contribution of SPARC down-regulation to the major aspects of the transformed phenotype, we have reexpressed this protein from a self-replicating retrovirus Rcas, designated R-SPARC, in the transformed cultures. These R-SPARC-infected cultures display the following main properties: (i) they accumulate the SPARC protein to a level identical to or only slightly higher than the level in normal chick embryo fibroblasts; (ii) they retain the main phenotypic properties characteristic of in vitro transformed cells, that is, altered morphology, capacity to grow in a reduced amount of serum, and capacity to develop colonies from single cells in agar; (iii) they display a clearly reduced capacity to develop local fibrosarcomas in vivo. Taken together, these data strongly suggest that down-regulation of SPARC contributes to the transformed phenotype triggered by vSrc and vJun in primary avian fibroblasts, by facilitating in vivo tumorigenesis.

Animals↗
PubMed1992

Regulation of the malic enzyme and fatty acid synthase genes in chick embryo hepatocytes in culture: corticosterone and carnitine regulate responsiveness to triiodothyronine.

Triiodothyronine (T3) added to chick embryo hepatocytes between 20 and 68 h of culture caused a 30- to 40-fold increase in malic enzyme activity. This T3 response decreased as a function of time; after 1 week in culture, a 48-h incubation with T3 had no effect on hepatocyte malic enzyme activity. Neither corticosterone nor carnitine had a significant effect on malic enzyme activity in the absence of T3 at any time or on the response of malic enzyme to T3 during the first 68 h of culture; both stimulated responsiveness to T3 subsequent to 68 h. The effects of corticosterone and carnitine on malic enzyme activity were additive, suggesting different mechanisms. Corticosterone and carnitine regulated abundance of malic enzyme mRNA. For corticosterone, at least, this effect was due to regulation of transcription. Abundance of fatty acid synthase mRNA was also stimulated by T3 in chick embryo hepatocytes in culture, and its responsiveness to T3 decreased with time. Corticosterone and carnitine stimulated responsiveness to T3 at times subsequent to 68 h. Corticosterone had no effect on binding of T3 to nuclear receptors. Intracellular accumulation of long-chain fatty acids or long-chain acyl-CoAs probably did not cause the loss of responsiveness to T3 or the stimulation of that responsiveness by corticosterone or carnitine because adding serum albumin (0.5%) or long-chain fatty acids (0.25-0.5 mM) to the medium was without effect. Corticosterone and carnitine may control the levels of other metabolic intermediates or protein factors which, in turn, regulate the transcriptional response of the lipogenic genes to T3.

Actins↗
PubMed2006

BMP is an important regulator of proepicardial identity in the chick embryo.

The proepicardium (PE) is a transient structure formed by pericardial coelomic mesothelium at the venous pole of the embryonic heart and gives rise to several cell types of the mature heart. In order to study PE development in chick embryos, we have analyzed the expression pattern of the marker genes Tbx18, Wt1, and Cfc. During PE induction, the three marker genes displayed a left-right asymmetric expression pattern. In each case, expression on the right side was stronger than on the left side. The left-right asymmetric gene expression observed here is in accord with the asymmetric formation of the proepicardium in the chick embryo. While initially the marker genes were expressed in the primitive sinus horn, subsequently, expression became confined to the PE mesothelium. In order to search for signaling factors involved in PE development, we studied Bmp2 and Bmp4 expression. Bmp2 was bilaterally expressed in the sinus venosus. In contrast, Bmp4 expression was initially expressed unilaterally in the right sinus horn and subsequently in the PE. In order to assess its functional role, BMP signaling was experimentally modulated by supplying exogenous BMP2 and by inhibiting endogenous BMP signaling through the addition of Noggin. Both supplying BMP and blocking BMP signaling resulted in a loss of PE marker gene expression. Surprisingly, both experimental situations lead to cardiac myocyte formation in the PE cultures. Careful titration experiments with exogenously added BMP2 or Noggin revealed that PE-specific marker gene expression depends on a low level of BMP signaling. Implantation of BMP2-secreting cells or beads filled with Noggin protein into the right sinus horn of HH stage 11 embryos resulted in downregulation of Tbx18 expression, corresponding to the results of the explant assay. Thus, a distinct level of BMP signaling is required for PE formation in the chick embryo.

Animals↗
PubMed2002

Homocysteine modifies development of neurulation and dorsal root ganglia in chick embryos.

BACKGROUND: The formation of the neural tube (neurulation) involves two mechanisms: primary and secondary neurulation. In chicks, there is also an overlap zone, where both mechanisms work together. Homocysteine (Hcy) may have an important teratogenic role in neural tube defects (NTD) when folic acid levels are considered normal. Recently, Hcy capability to generate NTD and modify neural crest cell migration has been demonstrated in chick embryos. This study was aimed to evaluate the effects of Hcy on neurulation and the development of the dorsal root ganglia (DRG). METHODS: Chick embryos were treated with L-Hcy thiolactone 20 micromol to produce the highest rate of survival with embryos carrying neural tube defect (NTD) in the spine. Embryos at stages (st) 3-10 were treated and harvested at st 18-23. Only externally normal embryos or those carrying spinal NTD embryos were considered. RESULTS: Histological sections of Hcy-treated embryos showed: open spina bifida (39% of embryos), more than one tube forming the spinal cord (26%), disorganized spinal cord (26%), always affecting lumbosacral regions, probably in the overlap zone. Additionally, 32% of embryos had small and continuous DRG, associated with a slimmed roof plate. Three-dimensional reconstruction showed unsegmented DRG until the C8 ganglion level. There was a 75% reduction of C3 DRG cells in treated embryos in comparison to untreated ganglia. CONCLUSION: Hcy teratogenicity in avian embryos affected the neural tube in the overlap zone, secondary neurulation and the cervical DRG.

Animals↗
PubMed1980

Development of sensitivity to acetylcholine in cultured chick embryo sympathetic ganglion neurones.

Dissociated sympathetic neurones from chick embryos of various ages were maintained in culture for several days and changes in sensitivity to iontophoretically applied acetylcholine (ACh) measured over 5 days in vitro. Neurones from 12-day embryos show a marked increase in ACh sensitivity, neurons from 14-day embryos a smaller change and those from 19-day embryos do not alter. These changes parallel those observed previously for binding of [125I]alpha-bungarotoxin.

Acetylcholine↗
PubMed2006

Influence of hypothyroidism induced by thiamazole on the toxicity of amitriptyline in chick embryos.

The effect of hypothyroidism induced by thiamazole on the toxicity of amitriptyline was studied in chick embryos. Fertilized eggs of White Leghorns were incubated and investigated. 1.2 mg/0.2 ml/egg of thiamazole was injected into the albumen of fertilized eggs on the 9th day of incubation. The control group was given 0.2 ml/egg of physiological saline in the same manner. Amitriptyline at 1 mg/egg was injected into the air sac of fertilized eggs on the 16th day of incubation. Electrocardiograms were recorded 0 to 60 min after the injection. After the injection of amitriptyline into the thiamazole-treated eggs, the heart rate was significantly decreased compared with the untreated eggs. These findings indicate that hypothyroidism induced by thiamazole has a marked influence on the toxicity of amitriptyline in chick embryos.

Amitriptyline↗
PubMed1966

Amniotic contraction and embryonic motility in the chick embryo.

During part of the incubation period of chick embryos the amnion shows spontaneous contractions. Removal of the amnion on days 9, 10, and 11 has no effect on the amount of, or the cyclic aspects of, motility exhibited by the embryo. These observations question the importance of the amnion and yolk-sac as stimulative factors in the initiation and maintenance of cyclic embryonic motility at the ages studied.

Amnion↗
PubMed1991

Muscle-derived factors enhance cholinergic neuronal expression in the chick embryo--I. In ovo studies.

The effects of muscle-derived factors were studied in the chick embryo in ovo, during early neuroembryogenesis. Limb muscle extract (LME) administration during embryonic period E1-E7 produced a significant increase in choline acetyltransferase activity of both spinal cord and brain in 8-day-old chick embryos. Similar treatment failed to induce significant change in the GABAergic phenotypes as assessed by the activity of the enzyme glutamic acid decarboxylase. Administration of limb muscle extract at either embryonic days 1-3 or 4-7 produced a significant increase in choline acetyltransferase activity in the brain, indicating that the critical period of limb muscle extract in the brain to be between embryonic days E1 and E7, a period of neuronal proliferation and differentiation in the brain. On the other hand, LME administration produced no effect on spinal cord choline acetyltransferase activity when given at embryonic days 1-3, whereas it produced a marked increase when given at embryonic days 4-7. Thus, the critical period of limb muscle extract effect in the spinal cord appears to be confined to embryonic days E4-E7, a period of neuronal differentiation and cell death in the spinal cord. These findings indicate that the cholinotrophic activity of muscle-derived factors is not limited to the muscle target tissues but have a general effect on cholinergic neurons in the CNS. Whether these cholinotrophic effects are mediated by a common factor or by different factors is still under investigation.

Animals↗
PubMedDate not supplied

Cardioteratogenic dose of ethanol in the chick embryo results in albumin ethanol concentrations comparable to human blood alcohol levels.

Three-day-old chick embryos (Hamburger-Hamilton stages 18-19) were exposed to a dose of ethyl alcohol (0.32 ml of 50% ethanol) that causes cardiac malformations in 96.6% of the animals. Ethanol was administered into the air sac after 72-80 h of incubation. Samples of albumin at the opposite pole of the egg were drawn 0-50 h after treatment and quantitated for ethanol concentration with capillary gas-liquid chromatography. Ethanol concentrations in the albumin increased significantly (P < 0.05) at 2, 5 and 15 h after injection of ethanol, reached a maximum mean ethanol concentration at 20 h (217.3 +/- 23.5 mg dl-1), decreased significantly at 30 h to 175.4 +/- 27.5 mg dl-1, then increased again and stabilized at 40-50 h. Individual sample concentrations ranged from 0 mg dl-1 (at 0.5-2 h) to 286.5 mg dl-1 at 40 h. Ethanol concentrations in the albumin were comparable to human blood alcohol levels during intoxication (> 150 mg dl-1). Our results suggest that a potent cardioteratogenic dose of ethanol in the chick embryo is reasonable in terms of potential human embryo exposure.

Animals↗