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At least 811 records · Page 45Linked to original sources

PubMed1992

Cyclophosphamide and its metabolite acrolein. Some studies on their porphyrinogenic action in 17 day old chick embryo.

1. Some studies of cyclophosphamide (CP) and its metabolite acrolein in chick embryo liver were carried out in order to investigate the mechanism of the porphyrinogenic action of CP. 2. In vitro and in vivo studies revealed that CP induced but did not activate delta-aminolaevulinic acid (ALA) synthase. 3. Pretreatments with phenobarbital (PB) or SKF-525A did not modify ALA-synthase induction produced by CP. 4. Acrolein administration neither induced ALA-synthase activity nor increased cytochrome P-450 content or led to hepatic porphyrin accumulation. 5. Time course induction of cytochrome P-450 content after administration of CP or PB was similar. 6. The results obtained would indicate that CP is a strong inducer of both ALA-synthase activity and microsomal cytochrome P-450 content in liver of 17 day-old chick embryos and that its porphyrinogenic activity is not mediated by its metabolite acrolein.

5-Aminolevulinate Synthetase↗

PubMed1989

Mitosis and cell death in the tail of the chick embryo.

Although somites develop from the mesoderm in the tail of the chick embryo, they do not form to the tip of the tail. Previous work has shown that this terminal mesoderm possesses many of the characteristics of the segmental plate mesoderm which gives rise to the somites in the trunk. This investigation is aimed therefore at understanding why the terminal mesoderm fails to form somites. Mitotic and pyknotic rates have been obtained for the tail region of chick embryos between stages 13 and 27. Embryos were treated with colchicine, so that the mitoses were blocked in metaphase, and counts were made on serial sections. The overall mitotic rates were highest between stages 15 and 18. Regions of high mitotic rate, which are an indication of cell synchrony, were found in the tail bud mesoderm though not in a consistent location, and only infrequently near the anterior end of the tail segmental plate. In the trunk however (Stern and Bellairs 1984) a single peak of cell synchrony was routinely found near the cranial end of the segmental plate. It is concluded that the cells of the tail mesoderm are less synchronised in preparation for somitogenesis than are the corresponding mesoderm cells in the trunk. A further conclusion is that the tail bud is not per se a region of high proliferation, though there are patches of high mitotic rate. The overall pyknotic rate reached a maximum at stage 25; peaks of pyknosis corresponded initially with the mitotic peaks and were associated with the ventral ectodermal ridge and the tail gut. By stage 25 however, the high levels of cell death were restricted mainly to the tip of the tail.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Early development and tissue-specific patterns of insulin binding in chick embryo.

We studied the development of insulin binding to its receptor in chick embryos from days 2-18 of the 21-day incubation period. Using partially purified membrane preparations we found that insulin receptors on both brain and liver of day 18 embryos were typical insulin receptors by multiple criteria. Specific insulin binding to preparations of whole embryos was not detected on day 2, but was present by day 3. Insulin receptors were present on both heads and bodies of embryos by day 4. Binding to liver and brains increased with development between days 8 and 18; however, the patterns of increase in the two tissues were quite distinct. In liver, binding was low on day 8, but increased markedly by day 14 (P less than 0.01). Increases after day 14 were less impressive. In contrast, binding to brain preparations was relatively well established by day 8 and did not change significantly between days 8 and 14. An abrupt increase occurred between days 14 and 16 (P less than 0.01), and a second increase took place between days 16 and 18. We have previously shown that insulin is present in chick embryos before known pancreatic development. The current demonstration that insulin receptors are also present early in embryogenesis makes it possible that insulin may influence the embryo at early stages. In addition, the different patterns of increases in insulin binding in liver and brain during mid- to late development suggest complex and tissue-specific mechanisms of regulation.

Animals↗

PubMed1985

A study into the effects of 2-acetylaminofluorene on hepatic monooxygenase activities in the chick embryo.

2AAF is a potent inducer of cytochrome P-450 in the chick embryo liver. The induction has been characterized with respect to a range of monooxygenase activities and the regiospecificity of 2AAF hydroxylation. Similarities to the response elicited by both PB and 3MC were noted. 2AAF was rapidly deacetylated by hepatic microsomes prepared from control animals to 2AF, an inhibitor of monooxygenase activity. Metabolites generated in vivo and carried over in vitro might have therefore interfered with the subsequent kinetic analysis. In general terms induction of a unique cytochrome P-450 subform(s) could not be attributed to 2AAF in the chick embryo. The data is discussed with respect to the reported resistance of avian species to the hepatocarcinogenic effects of 2AAF. Two possibilities are highlighted, a diversion of 2AAF to ring hydroxylated metabolites and/or deacetylation of 2AAF. Both effects could reduce carcinogenicity by decreasing the concentration of proximate carcinogen and/or promoter(s).

2-Acetylaminofluorene↗

PubMed1983

Corticosteroid receptors in the kidney of chick embryo. I. Nature and properties of corticosterone receptor.

Cytosol from kidney of chick embryo (age 16-18 days) contained a corticosterone-binding site with the features of a putative receptor. This receptor was a thermolabile protein, readily digested by proteolytic enzymes, with a sedimentation coefficient of 7-8 S and with an apparent molecular weight greater than 100,000. Simultaneous studies with transcortin (CBG) revealed several differences between the renal- and serum-binding protein pertaining to the effect of temperature, the sedimentation coefficient, the charcoal "stripping" and, finally, the binding and competition of various steroids for the two proteins. Kinetic analysis showed a rapid association (10 min), which followed second-order reaction kinetics, and a dissociation of pseudo-first-order reaction kinetics with a t1/2 of 168 min at 0 degrees. The analysis of the Scatchard plot showed the presence of a single class of binding sites with an association constant (KA) of 1.3 X 10(8)M-1 and a binding capacity (nmax) of 500-700 fmol/mg protein. We obtained similar results when we used dexamethasone as a ligand. The association (ka) and dissociation (kd) rate constants were respectively 2.9 X 10(6)M-1 sec-1 and 6.86 X 10(-5) sec-1. From their ratio a KA value of 4.2 X 10(10) M-1 was obtained. Studies with various steroids demonstrated that only dexamethasone and, to a lesser degree, progesterone competed for the binding site. These data showed that the kidney of chick embryo possessed one type of receptor for the glucocorticoids, which was similar to the type II described in rat kidney.

Animals↗

PubMed1954

Some observations on the intracellular localization of the virus of herpes simplex in the chick embryo liver.

The growth cycle of the virus of herpes simplex in chick embryo liver has been shown to follow the same pattern as in the chorioallantoic membrane and the rabbit's corneal cells. However, there is considerable variability in the time taken for the yolk sac-inoculated virus to get from the yolk sac into the liver. A brief description has been given of various fractionation procedures employed for obtaining isolated nuclei. It has been shown that free virus is not selectively adsorbed to isolated nuclei. Evidence has been presented to show that in the herpes-infected chick embryo liver, large proportions of the total virus can at times be found associated with the nuclear fraction. The percentage of the total virus in the nuclear fraction varies inversely with the titer of virus in the whole liver, and the number of hours after inoculation of the virus; only a negligible amount (as compared with that in the total) being associated with the nuclear fraction when a period of over 12 hours has elapsed after reappearance of virus. Furthermore, demonstration of virus in the isolated nuclei following extraction with hypertonic NaCl provides additional evidence that this virus is intimately associated with the nuclei.

Animals↗

PubMed1976

Effect of selenium and mercury on gross morphology and histopathology of chick embryos.

Gross lesions of selenium toxicity in chick embryos included webbed, fused, and curled toes; cracked, crooked, and shortened beaks and gastroschisis. Mercury injection on day 3 of incubation caused leg defects but older embryos were much less susceptible. Histopathological studies showed that injection of selenium as selenite caused dissociation of hepatic cells, particularly around the central veins. Glomeruli of affected kidneys were enlarged, and in each glomerulus the lumen of the capillary tuft was dilated and the space of Bowman widened. Epithelial cells of the proximal convoluted tubules were detached from the basement membranes. Injection of mercury as chloride resulted in liver pathology in the late dead embryos which included dilated central veins and sinusoids. The cytoplasm of many hepatic cells was vacuolated. Foci of hemorrhages were observed in all liver lobes. In the kidneys, the renal corpuscles showed either shrinkage or enlargement. They seemed to be in the process of degeneration and disintegration. Sclerotic glomeruli were characterized by disappearance of Bowman's space and clumping of the glomerular tuft. Combined treatment with selenium and mercury resulted in liver pathology similar to that observed in mercury toxicity. The hepatic cell dissociation seen in selenium treated embryos was not observed following the combined treatment. In the kidneys the combined treatment resulted in typical lesions of both selenium and mercury toxicity.

Abdomen↗

PubMed1953

Tissue culture studies; isolation of the active components in the ultrafilterable portion of the chick embryo extract.

A fraction of the ultrafilterable portion of chick embryo extract was isolated by alcohol extraction of a lyophilized powder of the ultrafiltrate followed by ion exchange removal of many of the inert components of the alcohol extract. This fraction contained 3 per cent of the ultrafilterable nitrogen but was capable of completely restoring the growth-promoting activity of dialyzed embryo extract, when tested with chick heart fibroblasts in roller tube cultures. The low nitrogen content, shape of the ultraviolet absorption spectrum, and presence of few free amino acids, suggest that non-dialyzable compounds serve as the chief source of nutrition for this system.

Animals↗

PubMed1977

[Influence of L.5-hydroxytryptophan (L.5-HTP) on the development of chick embryo].

L.5-hydroxytryptophan (L.5-HTP) injections provoke, in the chick embryo, some malformations of the nervous system, when treated at 24 hours of incubation. The same treatement after 48 hours of incubation does not lead to malformations, but to a reduction in size which is as much obvious as the embryos are treated at a later stage. It seems that there could be some relation between the serotonin metabolism and the growth hormon secretion.

5-Hydroxytryptophan↗

PubMed1995

Endogenous basic fibroblast growth factor is implicated in the vascularization of the chick embryo chorioallantoic membrane.

Chorioallantoic membrane (CAM) and chorioallantoic fluid (CAF) of the chick embryo were studied for the presence of immunoreactive and biologically active basic fibroblast growth factor (bFGF) from Day 6 to Day 18 of incubation. An immunoreactive M(r) 16,000 bFGF-like molecule was detected both in CAM and in CAF. This molecule was identified as bFGF on the basis of its molecular weight, its affinity for heparin, and its capacity to induce plasminogen activator production in cultured endothelial GM 7373 cells. The levels of biologically active and immunoreactive bFGF vary in CAM and CAF during embryonic development, maximal concentrations being observed between Days 10 and 14 of incubation. At all time points investigated, absolute concentrations of bFGF were significantly higher in CAM (ranging from 25 to 183 ng/g of wet tissue) than in CAF (ranging from 0.2 to 4 ng/ml). In a parallel series of experiments performed at Day 8 and evaluated at Day 12 of chick embryo development, human recombinant bFGF and neutralizing anti-bFGF antibody were investigated for their capacity to affect the vasoproliferative processes of the CAM. The two molecules either were applied onto the surface of the CAM or were injected into the allantoic sac. When bFGF or anti-bFGF antibodies were absorbed on methylcellulose discs and applied on the top of the CAM, they exerted a strong angiogenic or anti-angiogenic effect, respectively. On the contrary, when bFGF or the corresponding neutralizing antibody was injected into the allantoic sac, no modifications of the vasoproliferative processes of the CAM were observed at either the macroscopic or the microscopic level. These results provide evidence indicating that endogenous bFGF has a rate-limiting role in the vascularization of the CAM during chick embryogenesis. bFGF located within the CAM, rather than that present in the CAF, appears to be involved in this developmental process.

Allantois↗

PubMed2002

Melatonin potentiates phenylephrine-stimulated intracellular Ca2+ transient in smooth muscle cell of large arteries of chick embryo.

In the current study we first characterized the properties of the 2-[125I]iodomelatonin binding in pulmonary artery and aorta of chick embryo, and then determined the location of the binding site with autoradiography. Receptor binding assays were used using 2-[125I]iodomelatonin as ligand. The binding was stable, saturable, specific and reversible. Scatchard anlaysis revealed an equilibrium binding constant (Kd) of 27.12 +/- 1.34 pM and a maximum binding capacity (Bmax) of 1.93 +/- 0.19 fmol/mg protein (n = 5). Guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) increased the Kd, but reduced the Bmax, indicating the binding being coupled to a G-protein. Autoradiography revealed the binding sites in the smooth muscle layer. To delineate the physiological function of melatonin in the large artery of the chick embryo, we determined the intracellular calcium ([Ca2+]i) in smooth muscle cells of the aorta with spectrofluorometry, using fura 2-AM as calcium indicator. Melatonin at 10(-8) to 10(-5), which itself had no effect, potentiated the stimulating effect of 0.1 microM phenylephrine, a selective agonist of alpha -adrenoceptor, on [Ca2+]i. In conclusion, specific binding of 2-[125I]iodomelatonin and physiological response to melatonin suggest the existence of melatonin receptor in the smooth muscle of large arteries of the chick embryo. Melatonin potentiates the effects of alpha1-adrenergic stimulation.

Animals↗

PubMed1975

[Effect on drugs changing the intracellular level of adenosine 3',5'-cyclic monophosphate on interferon formation in chick embryo cells of different ages].

The effect of theophylline and adrenaline on the synthesis of interferon induced by the influenza B virus, strain Lee, in a chick embryo tissue culture was studied. Both preparation were found to decrease interferon synthesis when 5-day-old cultures were used; the inhibitory effect was increased when the two drugs were used together. The degree of inhibition of interferon production depended on a dose of the preparation; the inhibition was still present even when the drugs ere introduced several hours after the cells were infected with interferonogen. The treatment of one-day-old cultures with theophylline resulted in increase of interferon synthesis, whereas administration of adrenaline alone or together with theophylline did not affect the level of interferon synthesis. The drugs used produced no effect on the reproduction of the test-virus of vesicular stomatitis, Newcastle disease and Chickungunya viruses in chick embryo cells and influenza B virus in the developing chick embryos. The results obtained are discussed from the point of view of a possible influence of the intracellular adenosine 3',5-cyclic monophosphate level on the synthesis of virus-induced interferon.

Aging↗

PubMed1998

Developmental regulation of the 3-methylcholanthrene- and dioxin-inducible CYP1A5 gene in chick embryo liver in vivo.

The cDNA sequences for two dioxin-inducible cytochrome P450s in chicken, CYP1A4 and CYP1A5, have recently been reported which correspond to two dioxin-inducible forms of P450 previously designated as TCDDAHH and TCDDAA, respectively. The developmental expression of CYP1A4-associated aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) activity and its association with expression of the Ah receptor had previously been characterized in chick embryo liver. The purpose of this study was to examine the developmental regulation of the second dioxin-inducible P450 gene, CYP1A5, in chick embryo liver. A partial gene sequence for CYP1A5 indicated that the intron/exon organization of this gene was identical to that of the CYP1A1 and CYP1A2 mammalian genes and was present in a single copy in the genome. CYP1A5 mRNA was expressed basally in chick embryo liver and was highly inducible by the Ah receptor ligands, 3-methylcholanthrene, beta-naphthoflavone, and 3,4,3', 4'-tetrachlorobiphenyl (TCB), but not by the phenobarbital analog, glutethimide. CYP1A5 mRNA levels were increased 40- to 50-fold within 5 h after a single TCB treatment, corresponding to a 30- to 40-fold increase in the transcription rate of the CYP1A5 gene at this time point. In contrast to a previous report that CYP1A5 mRNA expression was inducible by estradiol, we observed no effects of estradiol or dexamethasone on CYP1A5 mRNA expression, either alone or in combination with TCB. Basal and TCB-inducible CYP1A5 mRNA expression was maximal in liver at 8 days of development and remained high throughout the remainder of embryonic development. Thus, CYP1A5 appears to be regulated in a very similar manner to CYP1A4 in chick embryo liver.

Animals↗

PubMed1983

Synthesis of globin chains in the erythropoietic sites of the early chick embryo.

The synthesis of globins in the chick embryo before the onset of circulation has been studied in situ by specific immunofluorescence labelling of embryonic sections and by labelling newly synthesized proteins in ovo and in vitro in embryonic explants with [3H]leucine. The presence of major primitive haemoglobins is observed by 28 h of incubation. The minor primitive haemoglobins become detectable by immunofluorescence after 40 h of development, shortly before the onset of circulation. 3H-labelling shows that one definitive alpha chain is synthesized, though in low concentration, from the initial globin detection. The other definitive alpha chain is observed in embryos of at least 40 h of development. The relative concentration of the two definitive alpha chains changes rapidly with development indicating a specific mechanism of regulation. An erythropoietic site is observed in the wall of the dorsal aorta in embryos of about 45-50 h of development. From the initial detection, those cells contain all four primitive embryonic haemoglobins, in contrast to what is observed for the cells of the blood islands.

Animals↗

PubMed1979

Nucleoside phosphotransferase of chick embryo.

This paper describes a purification procedure and some properties of a nonspecific nucleoside phosphotransferase of chick embryo, an activity which catalyzes the transfer of chick embryo, an activity which catalyzes the transfer of the phosphate ester from a deoxyribonucleotide or a pyrimidine ribonucleotide to a deoxyribonucleoside acceptor. The enzyme is very unstable to heat, dilution and dialysis and it is almost entirely inactivated by DEAE-cellulose chromatography or gel filtration. A marked enhancement in its stability is caused by numerous nucleotides. In these experiments at least 920-fold purification was obtained by using dTTP (50 microM) as nucleotide protector. The enzyme, purified in presence of dTTP, has a molecular weight about 270,000, an isoelectric point of 6.27, a pH optimum of 8.8 and is stable at 37 degrees C at least for 10 min. In absence of nucleotide protector, nucleoside phosphofranserferase is connected at 37 degrees C or by gel filtration in a very small active form with a lower molecular weight (about 30,000) and a pH optimum of 7.6.

Animals↗

PubMed1976

Submicrosomal localization of prolyl hydroxylase from chick embryo limb bone.

A fraction greatly enriched in microsomes was prepared from chick embryo limb bone tissue homogenates by differential centrifugation in a high density solution of Metrizamide. This fraction was used to determine the submicrosomal localization of prolyl hydroxylase. At a low concentration (0.05%) of the non-ionic detergents Triton X-100 and Brij-35, 90 to 93% of prolyl hydroxylase activity was released from microsomes. Concentrations of Triton X-100 greater than 0.1% were required to solubilize the intrinsic membrane enzyme NADH-ferricyanide reductase and to release membrane-bound ribosomes, while Brij-35 did not extensively solubilize membrane components even at concentrations up to 0.4%. In addition, prolyl hydroxylase activity which could subsequently be released from microsomes by Brij-35 was relatively resistant to trypsin proteolysis at concentrations which removed more than 50% of the ribosomes and approximately 40% of the protein from microsomes. These results suggest that 90 to 93% of prolyl hydroxylase activity in connective tissue is located within the cisternae of the endoplasmic reticulum. Gel filtration of prolyl hydroxylase released from microsomes or found in the soluble fraction of limb bone homogenates revealed two peaks of activity corresponding to molecular weights of 230,000 and 450,000 to 500,000. The latter is twice the value reported for purified chick embryo prolyl hydroxylase. A fraction of the total prolyl hydroxylase activity (generally 20 to 35%) in microsome preparations could be measured in the absence of detergent, although the microsomal membrane should be impermeable to the large unhydroxylated collagen chains used as substrate. On the basis of experimental data, it was concluded that detergent-independent activity was most likely due to damaged microsomal membranes and that this damage was sufficient to allow substrate and trypsin to enter the cisternae but not to allow prolyl hydroxylase to be released.

Animals↗

PubMed1993

Neural crest ablation versus sham surgical effects in a chick embryo model of defective cardiovascular development.

In chick embryos, ablation of premigratory neural crest destined for the third, fourth, and sixth pharyngeal arches results in persistent truncus arteriosus and interrupted aortic arch. Studies of cardiogenesis in these embryos have shown decreased ejection fraction and ventricular dilation with normal cardiac output. The experimental embryos that survive to d 11 of incubation have a higher cardiac output than nonsurvivors at the same earlier stage of development. We hypothesize that this survival is due to a surgically induced decrease in vascular resistance of the embryonic and vitelline vessels. Embryos from 15 opened eggs, eight sham-operated embryos, and 13 neural crest-ablated embryos were examined at stage 18. The sham-operated embryos were treated identically with the experimental embryos except that neural crest was not ablated. Ejection fraction and cardiac output were determined by cinephotography. Mean dorsal aortic and diastolic ventricular (approximates mean atrial) pressures were determined by a servo-null pressure technique and used to calculate vascular resistance. The experimental embryos had a significantly decreased ejection fraction in comparison with either sham-operated embryos or embryos from eggs that remained unopened until just before cinephotography. The experimental and sham-operated embryos had a higher cardiac output than embryos from unopened eggs. The calculated vascular resistance was also significantly lower in both the experimental and sham-operated embryos than in the embryos from unopened eggs. Neural crest ablation appears to cause a decreased ejection fraction. Sham surgery is associated with a higher cardiac output and lower vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

[Use of chick embryos for prediction of embryotoxic effects of mycotoxins in mammals].

Embryotoxic effects of 25 mycotoxins were investigated in two-, three- and four-day chick embryos; the results were evaluated on the eighth day of development. The embryotoxicity ranged from 0.0001 to 0.1 microgram per embryo in T-2 toxin, aflatoxin B1, G1, B2 and M1, cytochalasin E, ochratoxin A and PR-toxin; from 0.1 to 1.0 microgram per embryo in sterigmatocystin, aflatoxin G2, vomitoxin (4deoxynivalenol), patulin, rubratoxin B, secalonic acid D, mycophenolic acid, and from 1.0 to 100 micrograms per embryo in penicillic acid, cyclopiazonic acid, tenuazonic acid, citrinine, brevianamide A, zearalenone, fusaric acid, griseofulvin, kojic acid and 8-methoxypsolaren. Acute cardiotoxic effects were observed in PR-toxin, patulin, rubratoxin B, penicillic acid, citrinine and zearalenone. Teratogenic effects with a spectrum of different embryonal malformations occurred in T-2 toxin, ochratoxin A, PR-toxin, patulin, secalonic acid D, mycophenolic acid and citrinine. The embryotoxic effects demonstrated in chick embryos correlated with the well-know literary data on mammals. Considering the different chemical composition and biological effects of mycotoxins, we suppose that the embryotoxicity test of chick embryos will also be suitable for testing other biologically active substances in the environment.

Animals↗