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PubMed1997

Cardiac output distribution in the chick embryo from stage 36 to 45.

OBJECTIVE: The distribution of cardiac output to different organs is well described in the mammalian fetus. Chick embryos are not often used in perinatal cardiovascular research and therefore it is not known whether they can serve as an animal model for this purpose. In this study we documented cardiac output distribution in chick embryos at increasing incubation time. METHODS: Fertilized eggs from day 10 to 19 with an incubation time of 21 days were studied in 3 increasing incubation time groups (10-13, 14-16 and 17-19 days). For the experiment, the egg was placed in a holder in an incubator. The egg was opened at the air cell and a small vein of the chorioallantoic membrane was catheterized. Twenty thousand fluorescent 15 microns microspheres in 0.2 ml were injected. After 5 min, the embryo was sacrificed and the different organs were dissected and digested for microsphere isolation and subsequent fluorescence analysis. RESULTS: The chorioallantoic membrane, which is the placenta equivalent of the chick embryo, received a relatively large fraction of the combined cardiac output: 52.08% (interquartile range [IQR] 12.67%) on days 10-13 and 40.95% (IQR 27.24%) on days 17-19. Relatively small fractions were distributed: to the heart 2.03% (IQR 1.58) on days 10-13 and 3.18% (IQR 1.95) on days 17-19, and to the brain 3.20% (IQR 1.80) on days 10-13 and 5.02% (IQR 3.39) on days 17-19. As incubation time advanced, the fraction of the combined cardiac output to the chorioallantoic membrane and yolk-sac decreased significantly in favor of the heart and brain. CONCLUSION: This distribution shows great similarity to the one found in the mammalian fetus. The chick embryo is an attractive model for perinatal cardiovascular research.

Allantois↗
PubMed1975

Plasminogen-independent fibrinolysis by proteases produced by transformed chick embryo fibroblasts.

The fibrinolytic activity of proteases secreted by chick embryo fibroblasts infected with Rous sarcoma virus was studied by use of a procedure in which a fibrin clot was formed with highly purified fibrinogen and thrombin above the cell layer. This procedure results in the formation of fibrin that is apparently a more suitable substrate for studies on fibrinolysis than is fibrin prepared by other methods. Since neither plasminogen nor serum were included in the assay system in the present studies, the fibrinolytic activity observed cannot be ascribed to the conversion of the plasminogen in serum to plasmin by a plasminogen activator produced by transformed cells. Our procedure, therefore, measures proteolytic activities other than those reported by previous investigators. Maintenance of some of the transformed phenotypes of Rous sarcoma virus transformed chick embryo fibroblasts such as morpholigical change and increased rate of glucose uptake apparently does not depend on the presence of plasminogen in the culture medium.

Animals↗
PubMed1980

Synthesis of delta-aminolaevulinate synthase in vitro using hepatic mRNA from chick embryos with induced porphyria.

Polyadenylated mRNA was isolated from chick embryo liver following induction of hepatic porphyria. The RNA was translated in vitro using a wheat germ cell-free system and delta-aminolaevulinate synthase was identified in the translation products by indirect immunoprecipitation. The enzyme was not apparent in the translation products of polyadenylated RNA from non-induced livers. The molecular weight of delta-aminolaevulinate synthase synthesized in vitro was 70000 and the protein was estimated to represent up to 5% of total products synthesised in vitro. These data demonstrate for the first time that induction of chick embryo liver delta-aminolaevulinate synthase activity in hepatic porphyria correlates with a large increase in the translational capacity of isolated polyadenylated RNA for this enzyme and, together with preliminary cDNA . RNA hybridization studies, indicate that an increase in the level of delta-aminolaevulinic synthase mRNA is responsible.

5-Aminolevulinate Synthetase↗
PubMed2000

Teratogenic effects of dilantin on thoraco-abdominal organs of developing chick embryos.

Congenital anomalies on some viscera like heart, liver and kidney have been investigated in chick embryos after a single injection of dilantin (3 mg/egg), a known antiepileptic drug, on 4th day of incubation. On 19th day of incubation, chick embryos were collected to observe the gross malformations and histological changes in heart, liver and kidney. On gross examination, visceroptosis (29%), thin anterior abdominal wall (28%), ectopia cordis (10%) and dextrocardia (1%) were observed. Histological examination of the kidney revealed glomerular degeneration in kidney while in liver, dilated central veins with degenerated hepatocytes were present. Longitudinal section of the heart showed thicker musculature specially of ventricles with a narrower lumen in comparison to that of the control. The results indicate teratogenicity of dilantin in developing chick embryos.

Animals↗
PubMed1985

Nerve growth factor induces neural differentiation in undifferentiated cell of early chick embryos.

Nerve growth factor (NGF) induced differentiation in postnodal pieces (PNPs) of stage 4 chick embryos. This induction was highly selective for neural tissue; no other structures developed in the NGF-treated PNPs. Furthermore, the number of PNPs showing neural differentiation was dependent on the concentration of NGF, but there was no correlation between the concentration of NGF (5-100 ng/ml) and extent of neuralization. The neural inducing capacity of NGF could be abolished by anti-NGF antibody. NGF-induced neural differentiation was accompanied by elevated intracellular levels of cyclic AMP. Exogenous cyclic AMP (175 micrograms/ml) was able to stimulate neural differentiation but, unlike NGF, induced other structures (e.g., notochord and pulsatile tissue). Overall results suggest that cells from chick embryos at developmental stages much earlier than previously thought are responsive to NGF and NGF or a a closely related substance may serve as a neural inducer in the chick embryo.

Animals↗
PubMed1985

Influence of spinal cord stimulation upon myosin light chain and tropomyosin subunit expression in a fast muscle (posterior latissimus dorsi) of the chick embryo.

Latissimus dorsi muscles of the chick consist of a slow (ALD) and a fast (PLD) muscle. The influence of chronic spinal cord stimulation in the chick embryo upon the expression of myosin light chains and tropomyosin subunits was investigated. Early in development the two muscles exhibited the same ratio of alpha- and beta-tropomyosin subunits. Later, in the slow muscle the ratio beta:alpha decreased and in chicken the amounts of the two components were about the same. In the fast muscle, the alpha-subunit increased and reached 66% in young chicken. In the fast muscle, the alpha-subunit increased and reached 66% in young chicken. In the In the early stages of embryonic development, both muscles accumulated slow and fast light chains. However, in ALD the amount of slow light chains was greater than that of fast light chains and the reverse was observed in PLD muscle. Later during development, the slow components decreased in PLD while the fast components increased; the reverse was observed in ALD muscle. The fast myosin LC3f has been detected in 18-day-old embryonic PLD. Chronic spinal cord stimulation at a low rhythm was performed from day 10 of embryonic development to day 15 or 16. In both muscles from spinal cord-stimulated embryos, the beta-tropomyosin subunit was lower than in control embryos. In ALD, the pattern of light chains was unaffected by chronic stimulation while in PLD muscle the slow and fast components were modified. In particular the ratio LCs:LCf was increased in spinal cord-stimulated embryos with regard to controls.

Animals↗
PubMed1997

Liver-enriched transcription factors, HNF-1, HNF-3, and C/EBP, are major contributors to the strong activity of the chicken CYP2H1 promoter in chick embryo hepatocytes.

Chicken CYP2H1 promoter constructs express strongly in chick embryo hepatocytes at a level comparable with that of Rous sarcoma viral promoter. We have identified the transcription factors responsible for the active CYP2H1 promoter. Binding sites for transcription factors were located within the first 160 bp of promoter sequence using promoter deletion experiments and DNase I footprint analysis. Sequence analysis revealed characteristic sites for the liver-enriched transcription factors of the HNF-1, HNF-3, and C/EBP families and for the ubiquitous factor, USF. Protein binding to these sites was established by gel mobility shift assays. Mutagenesis and transient transfection experiments demonstrated that these sites, in combination, were responsible for the strong promoter activity with a substantial contribution from HNF-1 and HNF-3. The promoter was also active in mammalian HepG2 and COS-1 cell lines where expression was dependent on the identified transcription factor binding sites but promoter activity in the HeLa cells was low. Transactivation experiments revealed that promoter expression could be activated through the appropriate binding sites by exogenously expressed rat HNF-1alpha or HNF-1beta, rat HNF-3alpha or HNF-3beta and chicken C/EBP alpha. Transcriptional synergism between HNF-1 and C/EBP was observed in these transactivation experiments. A Barbie box-like sequence overlapped the USF element but was not functional. The results demonstrate that liver-enriched transcription factors and USF direct strong expression of the CYP2H1 promoter in transiently transfected cells. By comparison, in vivo expression of this gene in uninduced chick embryo hepatocytes is low but markedly increased by phenobarbital. Drug induction may therefore substantially reflect derepression of this inherently active promoter.

Animals↗
PubMed1975

Nicotine effects on the acid mucopolysaccharide content of chick embryo cardiac jelly.

Histochemical studies were made on the developing chick embryo heart to determine the effects of nicotine on acid mucopolysaccharide content during the critical stages of the cardiac morphogenesis. Two-day old embryos were injected with the dosages of nicotine ranging from 1.5 to 3 mg per embryo. The embryos were studied on the 3rd and 4th days of incubation. For an evaluation of acid mucopolysaccharides, the staining procedures of Mowry (1958) and Saunders (1964) were employed. It was found that nicotine decreases the content of acid mucopolysaccharide in the developing cardiac jelly. In the control embryos, the cardiac tissues picked up very intense coloration. At lower dosages (Group A; 1.5 mg/egg), the staining response of the treated heart tissues containing acid mucopolysaccharides was moderate as compared to the control embryos. At higher dosages (Group B; 3 mg/egg), the cardiac tissues were faintly colored as compared to the embryos of Group A. It is possible that the cardiac lesions previously reported in the chick embryos following the administration of nicotine (Gilani, 1971) are due to the reduction of the amount of acid mucopolysaccharides in the developing cardiac jelly--a susceptible period of the genesis of heart.

Animals↗
PubMed1984

Elimination of ipsilateral retinotectal projections in mono-ophthalmic chick embryos.

There are two transient ipsilateral retinotectal projections in the chick embryo: a normal one, appearing with a similar projection pattern in both binocular and monocular embryos, and an additional abnormal projection appearing only in mono-ophthalmic embryos. The development and the elimination of the ipsilateral retinotectal projections in mono-ophthalmic chick embryos was investigated using horseradish peroxidase (HRP) and the fluorescent dye Rhodamine-B-Isothiocyanate (RITC) as tracers for axonal pathways. The mechanisms involved in the elimination of the ipsilateral fibers are discussed.

Animals↗
PubMed1999

Cis-acting elements in the 5'-flanking DNA of the malic enzyme gene regulate tissue-specific T3-responsiveness in chick embryo fibroblasts.

Triiodothyronine (T3) stimulates transcription of the malic enzyme gene in chick embryo hepatocytes (CEH), but not in chick embryo fibroblasts (CEF), even though the two cell types contain similar nuclear T3 binding activities (F. B. Hillgartner, W. Chen, and A. G. Goodridge, J. Biol. Chem. 267, 12299-12306, 1992). Based on Western blot analyses and gel electrophoretic mobility-shift assays, differences in mass of thyroid hormone receptor (TR)alpha or binding of TRalpha to T3 response element (T3RE) are not responsible for tissue-specific T3 responsiveness. Using transfection assays, we show that the primary T3RE in RCAS-TRalpha-CEF, cells that constitutively over-express TRalpha, is located downstream of the T3REs that are primarily responsible for T3 responsiveness in CEH and is only weakly functional in CEH. T3RE 2, the major T3RE of the malic enzyme gene in CEH is active in CEF when the construct does not contain additional malic enzyme DNA, but not in constructs containing DNA from -3858 to -3541 bp. Responsiveness conferred by T3RE 2 is inhibited in CEF and RCAS-TRalpha-CEF by three or more cis-acting elements downstream from T3RE 2. One element each was localized to fragments from -3622 to -3595 and -3561 to -3541 bp. The inhibitory effect of these elements was not observed in CEH and, although they cannot explain all of the difference in responsiveness in the two cell types, may contribute to the tissue-specific T3 responsiveness of the malic enzyme gene.

5' Untranslated Regions↗
PubMed1992

A segmented pattern of cell death during development of the chick embryo.

During the early development of the chick embryo, specific groups of cells die in characteristic patterns. In this study, Nile Blue sulphate staining was used to reveal a novel pattern of segmentally repeated cell death in the paraxial mesoderm of the chick prior to stage 23. This pattern varies according to the developmental stage of the embryo and shifts rostrocaudally, corresponding to progressing somite differentiation. Initially, during early somite differentiation, cell death is restricted to the rostral half of the somite (the rostral pattern of cell death). After the somite has differentiated into dermomyotome and sclerotome, dead cells appear in superficial tissues in a pyramidal pattern which lies in register (rostrocaudally) with the central part of the sclerotome. Finally, small bands of dying cells are seen between the neural tube and the expanding sclerotome. This third pattern (the ventral path) lies in register with the rostral part of the caudal half of the sclerotome. We show by fluorescent labelling of the migrating neural crest that these patterns of cell death correspond to the routes of neural crest migration. In addition, serial sectioning of stage 23 chick embryos confirms that the position of dying cells correlates with the known routes of neural crest migration and with the sites of development of certain neural crest-derived tissues.

Animals↗
PubMed1995

Pharmacological characterization of the rhythmic synaptic drive onto lumbosacral motoneurons in the chick embryo spinal cord.

The isolated spinal cord of the chick embryo generates episodes of rhythmic bursting in which sartorius (hip flexor) and femorotibialis (knee extensor) motoneurons exhibit characteristic patterns of activity. At the beginning of each cycle both sets of motoneurons discharge synchronously. Following this brief synchronous activation sartorius motoneurons stop firing at the time of peak femorotibialis activity, producing a period of alternation between the two sets of motoneurons. Intracellular recording from motoneurons has suggested that the pause is mediated by a synaptically induced shunt conductance. However, the pharmacological basis for this shunt and the nature of the excitatory drive to motoneurons is unknown. To address these questions we have investigated the pharmacology of the rhythmic, synaptic drive to lumbosacral motoneurons using local and bath application of several excitatory and inhibitory antagonists, and documenting their effects on motor output in E10-E12 chick embryos. Local application of bicuculline or picrotoxin over sartorius motoneurons abolished the pause in firing recorded from the sartorius muscle nerve. As a consequence, the pattern of sartorius and femorotibialis activity was similar and the motoneurons were coactive. The pause in sartorius firing was shortened following local application of the glycine antagonist strychnine the nicotinic, cholinergic antagonists mecamylamine, and dihydro-beta-erythroidine and several excitatory amino acid antagonists. Application of the GABA uptake inhibitor nipecotic acid depressed the slow potentials and discharge recorded from the sartorius muscle nerve. These findings suggest that the pause is determined primarily by synaptic inputs acting at motoneuron GABAA receptors with contributions from glycinergic, cholinergic, and glutamatergic inputs. The actions of locally applied GABA onto spinal neurons are consistent with these findings because the neurotransmitter depolarizes spinal neurons and reduces their input resistance. Local application of bicuculline, but not strychnine, onto segments containing femorotibialis motoneurons altered the amplitude and duration of femorotibialis discharge and changed the profile of the slow potentials recorded from the muscle nerve. This finding implicates GABAergic inputs in the regulation of femorotibialis discharge. The pause in sartorius firing was still present and a pause in firing appeared in each cycle of femorotibialis discharge following bath application of bicuculline or strychnine. The pause in both sets of motoneurons could be abolished by local application of the NMDA receptor antagonist AP-5 onto the motoneurons, but not by local application of bicuculline. This action of AP-5 was in contrast to its activity in normal Tyrode's solution where it shortened the pause slightly.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1980

Studies on the valyl-h-tRNA synthetase of chick embryo brain irradiated with 60Co gamma-rays, in vivo.

18-day-old chick embryos (Leghorn) were irradiated in vivo with 1,2,3,4,5 or 7 Gy 60Co gamma-rays (dose rate = 0.9 Gy/min). Twenty-four hours after irradiation the activity of valyl-tRNA synthetase isolated from the brains was determined and compared with that of the non-irradiated control. The aminoacylation activity was found to decrease exponentially as a function of the dose (D37 = 6 Gy). Irradiation caused a more pronounced decrease in valyl-tRNA synthetase activity in 18-day-old than in 14-day-old chick embryos and induced in the valine-dependent ATP-PPi exchange reaction less change than in the valyl-tRNA FORMATion. The exposure of 15-day-old chick embryos to a dose of 4 or 5 Gy induced, respectively, a 40 or 20 per cent increase in enzyme activity of VRS (prepared on day 19 of embryonic life) relative to the control. In these experiments a decrease of Km value for tRNA has been found. The change in the number of sulfhydryl groups was also investigated.

Amino Acyl-tRNA Synthetases↗
PubMed1981

[Effect of actinomycin D on the formation of the photoreceptor ultrastructure of the retina in the chick embryo].

The influence of actinomycin D on the ultrastructure of retina photoreceptors in 10, 11 and 12 day old chick embryos was studied. Actinomycin D was shown to provoke certain changes in the ultrastructure of differentiating retina visual cells as soon as 1 hour after injection. These changes involve segregation and diffusion of nucleoli, changes in mitochondrial matrix, destruction of their external membranes and cristae, changes in the diameter and length of canals of endoplasmic reticulum, disintegration of polysomes. The noted changes do not prevent a further differentiation of the internal segments - ellipsoid and paraboloid of visual cells, but considerably affect parametres of these organelles. The formation of membrane disks of photoreceptors is inhibited after a 24 hours incubation with the inhibitor, when actinomycin D was injected to 11 day old embryos. Injection of actinomycin D into 12 day old chick embryos, after a 24 hours incubation with the inhibitor, does not inhibit a formation of membrane disks of photoreceptors, but somewhat retards their differentiation. This effect may be associated with the transcription o mRNA for protein synthesis of the membrane disks, which presumably takes place on the 11th day of the chick embryo incubation.

Animals↗
PubMed1986

Transient stimulation of glucose metabolism by insulin in the 1-day chick embryo.

Effects of insulin upon glucose metabolism were investigated in chick embryos explanted in vitro during the first 30 h of incubation. Insulin stimulated the glucose consumption of the chick gastrula (18 h) and neurula (24 h), but had no effect on the late blastula (0 h:laying) and on the stage of six to eight somites (30 h). The increase in glucose consumption concerned both the embryonic area pellucida (AP) and extraembryonic area opaca (AO). AP responded to a greater extent (50%) and at a lower range of concentrations (0.1-1.0 ng/ml) than AO (30%; 1-100 ng/ml). Insulin had no effect on the oxygen consumption of blastoderms, whereas it stimulated the aerobic lactate production (approximately 70% of the additional glucose consumption was converted to lactate). The nanomolar range of stimulating concentrations suggests that insulin has a specific effect in the chick embryo, and that it could modulate glucose metabolism in ovo as well. The transient sensitivity of the embryo to insulin is discussed in relation to behavior of mesodermal cells.

Aerobiosis↗
PubMed1979

Effects of furazolidone in the early chick embryo.

Effects of furazolidone in early chick embryos were investigated in order to determine the feasibility of using this biological system as a model for studying the mechanism(s) of furazolidone toxicity. Double and triple injections of varying dosages of furazolidone were administered via the yolk sac at early stages of incubation. Toxic levels of the drug affecting both growth and levels of glycogen were dosage-dependent and time-dependent. Double injections of furazolidone at a dose as little as 60 microgram/egg administered at 40 and 72 hr of incubation significantly retarded growth (P less than .001) and increased glycogen levels (P less than .05) in the embryo and yolk sac. Mortality was high in embryos receiving toxic levels of furazolidone, but no gross abnormalities were observed.

Animals↗
PubMed1976

[Effect of ionizing radiation on the activity of liver acid phosphatase in chick embryos and chickens].

The treatment of chick embryos and chickens at 1000 rad leads to the decrease of the total activity and the increase of the free activity of the acid phosphatase in the liver. These changes are mostly manifested at the 72nd hour following irradiation. The electron-microscopic studies reveal secondary lysozomes (cytolyzomes) full of round or elongated structures of varying density. All changes are most strongly manifested in 12-day-old embryos, and are most weakly manifested in 20-day-old ones.

Acid Phosphatase↗