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PubMed1988

GABAergic neurons in cultures derived from three-, six- or eight-day-old chick embryo: a biochemical and immunocytochemical study.

Cultures were prepared from 3-, 6- and 8-day-old chick embryos. Whole chick embryos were dissociated by sieving through a nylon mesh for E3 cultures and cerebral hemispheres for E6 and E8 cultures. The dispersed cells were plated onto poly-L-lysine coated culture dishes in Dulbecco's modified Eagle's medium, containing 10% fetal bovine calf serum. Growth patterns in these cultures have been previously described. Biochemical and immunocytochemical markers were used to identify GABAergic neurons in culture. Neurons exhibiting GABA-like immunoreactivity were present in all 3 types of cultures as early as 4-6 days in culture. The developmental profile of glutamic acid decarboxylase (GAD) derived from 3-day-old whole chick embryo cultures showed low activities whereas the enzyme activity markedly rose in cultures derived from 6- or 8-day-old chick embryo cerebral hemispheres during the first two weeks. The changes in GAD activity observed in these cultures are interpreted to reflect the maturational state of GABAergic neurons and also their responsiveness to microenvironmental factors.

Animals↗

PubMed1979

Naegleria fowleri in chick embryos. Effects of embryo age and incubation temperature, and the infectivity of embryo-derived amebae for mice.

Chick embryos were infected with Naegleria fowleri which was initially isolated from an ultimately fatal human case. Following inoculation of equivalent numbers of amebae on the chorioallantoic membrane, younger embryos died earlier than older embryos infected at the same time. Incubation of infected embryos at 32 degrees C prolonged survival only slightly in comparison with those at 37 degrees C. N. fowleri maintained for more than 25 serial passages in chick embryos retained infectivity for mice and the ability to convert to the biflagellate form in vitro.

Age Factors↗

PubMed1979

Fibronectin alters the phenotypic properties of cultured chick embryo chondroblasts.

The state of chick embryo chondroblasts in culture was found to be sensitive to both fibronectin and another substance(s) (activity A) which could be extracted from chick embryo fibroblasts with 1 M urea or from conditioned medium. In the presence of either of these activities at concentrations of 25-150 micrograms/ml, chondroblasts, which normally grow as mixed cultures of floating and adherent cells, all immediately became attached to the tissue culture dish and spread. After several days, the morphology of these typically epithelioid cells became fibroblastic. This did not involve a selection process, since the effect was reversible. The synthetic program of these cells was also dramatically modified: the cultures no longer synthesized the chondroblast-unique type IV sulfated proteoglycan and began synthesizing alpha 2 collagen chains typical of fibroblastic or early limb bud cells. Fibronectin was resolved from activity A by gelatin affinity chromatography or gel filtration. Both activities were trypsin-sensitive. The two activities differed, however, on the basis of how the protein fractions in which they were found migrated in SDS-polyacrylamide gels, their specific activities and their effects on cell morphology and cell growth.

Animals↗

PubMed1992

A factor derived from chick embryo retina which inhibits DNA synthesis of retina itself.

Chick embryo retinas contain a peptide factor that inhibits DNA synthesis in explants of chick embryo retina. The inhibitory factor, obtained by acid/ethanol extraction from 15-day-old chick embryo retinas, was partially purified by affinity chromatography on heparin-sepharose CL-6B and gel filtration on Sephadex G-100. The inhibitor reduced DNA synthesis with maximal effects observed in retinal explants from 7 to 8-day-old chick embryos. The inhibitory effect became apparent after 10 h of incubation and reached the maximum levels after 16 h. DNA-inhibiting activity was heat and acid-stable and was destroyed by trypsin and alkaline treatments. The inhibitory effect was observed in retinal explants incubated in a medium free from L-glutamine, and the addition of this compound to the medium reduced the inhibitory effect in a concentration-dependent manner.

Animals↗

PubMed1984

Capillaries and muscle fibers in the heart of the hyperoxic chick embryo.

Cardiomegaly was induced in chick embryos by incubation in 60% O2. On day 18 sections of heart were taken from these and from controls matched by egg weight before incubation in 21% O2. The ratio of left/right ventricular weight was the same in the two groups and so was the concentration of water in the ventricles. The densities of capillaries and of muscle fibers were determined in seven selected myocardial regions in order to establish (1) the cellular nature of the cardiomegaly, and (2) the effect of elevated O2 on capillary growth. In five of the regions no significant difference in capillary density was seen, but the cross-sectional area of the fibers rose significantly in all seven, especially in the right ventricle. Capillary density increased in the hyperoxic group in two areas immediately adjacent to the lumen of the right ventricle. These results suggest that oxygen causes hypertrophy of cardiac muscle fibers in the chick embryo without altering the capillary supply.

Animals↗

PubMed1979

A lectin which binds specifically to beta-D-galactoside groups is present at the earliest stages of chick embryo development.

Extracts obtained from chick embryos at the pre-gastrula and gastrula stages are able to agglutinate trypsinized rabbit erythrocytes fixed with glutaraldehyde. Agglutination is inhibited by saccharides sharing a beta-D-galactopyranoside configuration. Agglutinin activity is also inhibited by desialysed fetuin which bears terminal galactose residues but not by native fetuin, desialysed agalacto-fetuin, bovine submaxillary mucin and desialysed bovine submaxillary mucin. Lectin activity is present in extracts obtained from the embryonic area of the blastoderms as well as in extracts from extra-embryonic endoderm and ectoderm. In extracts subjected to gel filtration on ECD Sepharose, lectin activity eluted between ovalbumim (mol. wt 45 000) and chymotrypsinogen (mol. wt 25 000). Under some experimental conditions, thiodigalactoside, the most potent inhibitor of lectin activity, inhibited the aggregation of cells of the extra-embryonic endoderm of the primitive chick embryo.

Animals↗

PubMed1989

Effect of heart rate increase on dorsal aortic flow before and after volume loading in the stage 24 chick embryo.

In the stage 24 chick embryo, a paced increase in heart rate reduces stroke volume, presumably by rate-dependent decrease in passive filling. We hypothesized that rate-dependent stroke volume reduction could be abolished by volume loading. Dorsal aortic blood velocity was measured with a 20 mHz pulsed-Doppler meter from a 0.75-mm piezoelectric crystal (eight embryos), and atri-oventricular velocity was simultaneously measured from the ventricular apex (six embryos). Sinus venosus pacing (stimuli of 1 ms duration and less than 4 mA) was performed at intrinsic rate (P:I) and at 150% of intrinsic rate (P:150%I). Volume loading was performed during P:150%I by intravenous injection of 7.5 microL of chick Ringer's solution. Using atrioventricular velocity profile, stroke volume was divided into the proportion due to passive (E-phase) and active (A-phase) filling. Stroke volume was compared during P:I, P:150%I, immediately (P:150%I') and 30 s after (P:150%I") volume loading. Data (mean +/- SEM) were compared by ANOVA. During pacing, stroke volume (mm2/cycle) decreased but increased after volume loading (I, 0.43 +/- 0.03; P:I, 0.37 +/- 0.03; P:150%I, 0.19 +/- 0.03; P:150%I', 0.24 +/- 0.05; P:150%I", 0.28 +/- 0.04 (p less than 0.005). During P:150%I, E-phase filing disappeared and was not restored by volume loading, whereas, A-phase filling diminished but was restored by volume loading. In stage 24 chick embryos, rate-dependent stroke volume decrease is reversed by volume loading that restores stroke volume due to an increase in active filling but not passive filling. Thus, even at rapid heart rate, the embryonic ventricle responds to volume loading, indicating that the Frank-Starling relationship functions during tachycardia in the embryonic heart.

Animals↗

PubMed1979

[Subcellular localization of low-molecular RNA in the cells of chick embryos].

The subcellular distribution of chick embryo low molecular weight RNAs has been studied by the thermal phenol fractionation procedure. The major part of 8SII RNA, earlier discovered in some oncornaviruses and normal cells, was extracted by phenol at 4%. Our results thus give evidence of the cytoplasmic localization of this RNA. Another part of 8SII RNA, which has been extracted at 65 degrees, is thought to consist of newly synthesized molecules located in the nuclei. A similarity in subcellular distribution of low molecular weight RNAs from chick embryo and rat liver has been obtained, i. e. such a distribution may be of universal nature.

Animals↗

PubMed1985

Protein synthetic patterns of tissues in the early chick embryo.

Tissues dissected from early chick embryos were labelled in vitro with [35S]methionine, and their patterns of polypeptide synthesis investigated using the technique of two-dimensional (2-D) polyacrylamide gel electrophoresis. Apart from providing a preliminary description of the molecular changes associated with the processes of gastrulation and segmentation in the chick embryo, this study has revealed a number of polypeptides that may be useful as markers of cell type or function. The protein synthetic patterns of hypoblast from early and late gastrulae (stages 2 and 4, respectively: Hamburger & Hamilton, 1951) and of definitive endoblast and junctional endoblast from late gastrulae all resemble one another closely, but differ markedly from that of the epiblast at either stage. The lower layer tissues are characterized by the presence of eleven polypeptides that are largely absent from the epiblast. These findings are discussed with reference to current theories on the origins of the lower layer tissues. Comparisons between the 2-D patterns for tissues dissected from gastrulae and from embryos undergoing segmentation (stage 12) have revealed ten polypeptides showing stage-specific rather than tissue-specific expression. Apart from these ten polypeptides, the 2-D patterns for epiblast and ectoderm were practically identical, and distinguishable from those of other tissues by a lack of any unique polypeptides. On the other hand, stage-4 endoblast and stage-12 endoderm differed in the expression of many polypeptides. One polypeptide was found that may be considered as a marker of mesodermal cell type, as it was present in lateral plate, segmental plate and somitic mesoderm, but not in tissues of the other germ layers. Lateral plate could be distinguished from the other mesodermal tissues in the expression of a number of polypeptides, but the similarity in the 2-D patterns for segmental plate and somites suggest that the separation of somites from the anterior end of the segmental plate is not accompanied by the synthesis of new polypeptides.

Animals↗

PubMed1984

Effect of MPG on glucocorticoid-induced cataract formation in developing chick embryo.

Cataract in the developing chick embryo can be easily produced by administration of high doses of glucocorticoid and the cataract is preceded by a decreased level of glutathione in the lens (Nishigori et al, Exp Eye Res 36:617, 1983). In an attempt to prevent cataract formation, various natural and synthetic sulfhydryl compounds, glutathione, cysteine, ergothioneine, penicillamine, cysteamine and N-(2-mercaptopropionyl)glycine, were applied to hydrocortisone-treated developing chick embryos. N-(2-mercaptopropionyl)glycine showed the most potent delaying activity against cataract formation and also lessened the decrease of glutathione level in the lens. However, except for cysteamine, the other compounds tested had little or no effect.

Amino Acids, Sulfur↗

PubMed1985

Preventive effect of ascorbic acid against glucocorticoid-induced cataract formation of developing chick embryos.

Glucocorticoid administration to developing chick embryos is known to promote cataract formation with a decreasing level of glutathione in the lens. To gain further understanding of this process, the level of ascorbic acid, a biological antioxidant, in the lenses was measured during the course of glucocorticoid treatment. When 0.25 mumol of hydrocortisone hemisuccinate sodium (HC) were administered to 15-day-old chick embryos, the level of ascorbic acid in the lens began to decline after 30 hr and became around 40% of the control value at 48 hr after HC treatment. At this time about 90% of the lenses showed opacity in the nuclear region. However, the level of ascorbic acid in the cataractous lens recovered to the control level at 96 hr, a time when the lens has recovered from cataract formation. A triple application of ascorbic acid (20 mumol/egg) at 3, 10 and 20 hr after HC treatment significantly prevented lens opacification. The administration of ascorbic acid prevented the decline of ascorbic acid content and partially that of glutathione content in the lens caused by HC.

Animals↗

PubMed1987

Influence of hydrocortisone on chick embryo retina development.

Treatment of chick embryos in ovo with hydrocortisone-21-phosphate (a single dose of 150 micrograms) caused a marked reduction of retinal thymidine kinase activity 24 h later. The inhibitory effect was highest (65-70%) in 8-10-day-old embryos and declined with age, disappearing after day 15. It was accompanied by a reduction in thickness of the retinal layers. Adrenocorticotropic hormone (ACTH) treatment (10 micrograms daily for 2 days) also produced an age-dependent inhibitory effect on retinal thymidine kinase, whereas treatment with a single dose of 200 micrograms of metopirone, a compound that prevents the 11 beta-hydroxylation of steroid molecules in the adrenal glands, impeded the decrease in thymidine kinase activity that normally occurs in chick embryo retina after day 9 of development. In addition, metopirone prevented the inhibition exerted by ACTH on thymidine kinase activity but had no effect on the action of hydrocortisone.

Adrenocorticotropic Hormone↗

PubMed1987

The assembly of the DNA complex present in chick embryo cell cytosol.

Chromatography of chick embryo fibroblast cytosol labelled with [3H]thymidine or [3H]uridine precursors has shown the presence of early labelled DNA and RNA eluting at a position corresponding to a relative molecular mass of approximately 1.5-10(5). The early DNA-RNA (heteroduplex?) then moves progressively to a higher molecular weight peak, relative molecular mass approximately 10(6). The process appears similar in cytosol from cultured cells and from whole amniotically labelled chick embryos: consequently the cytosolic DNA complex is not an artefact of cell culturing. The relative contribution of artefactual and specific cytosol-associated DNA material is discussed: it is concluded that while both are present in cytosol as prepared, it is possible to discriminate between specific and artefactual DNA material.

Animals↗

PubMed1987

Type X collagen synthesis by cultured chondrocytes derived from the permanent cartilaginous region of chick embryo sternum.

In the developing chick embryo sternum, type X collagen is synthesized by chondrocytes from the cephalic region (presumptive mineralization zone) but not by chondrocytes from the caudal region (permanent cartilaginous zone) (Gibson et al., 1984, J. Cell Biol. 99, 208-216). To distinguish between two possibilities, the presence of a nonpermissive microenvironment in the permanent cartilage or the intrinsic inability of caudal chondrocytes to become hypertrophic, type X-producing cells, we have isolated chondrocytes from the caudal third of stage 44 chick embryo sterna and grown them in suspension on agarose-coated dishes. We have found that in these conditions chondrocytes from the caudal zone differentiate to hypertrophic chondrocytes and synthesize large amount of type X collagen, as revealed by the electrophoretic pattern of labeled proteins made in vitro and by slot blot analysis of mRNAs with specific cDNA probes.

Animals↗

PubMed1981

Lung development in the chick embryo. I. Phosphatidylcholine synthesis in the developing chick lung.

We investigated the relative contribution of the two pathways of phosphatidylcholine (PC) synthesis in lungs from chick embryos of 12 to 20 days of incubation as well as from hatched chicks and adult chickens. Lung "blocks" were incubated for 60 min in vitro in the presence of [3H]methionine and [14C]choline. PC was separated by thin-layer chromatography, and the amount of labeled product was determined by liquid scintillation counting. PC synthesis (expressed as pmoles PC per mg protein per 60 min) by the choline pathway declined from the 12-day value of 40 to a minimum of 8 at day 16 and then rose gradually to a peak of 74 on day 1 posthatching. PC synthesis via the phosphatidylethanolamine pathway also declined from day 12 (54) to day 16 (13) but peaked on day 19 (65) and again on day 1 posthatching (54). Synthetic activities of the two pathways differed significantly (P less than or equal to 0.05) only on days 14, 18, and 19 of incubation. Unlike the mammalian lung, neither pathway seems to predominate throughout incubation or after hatching. The increase in PC synthesis towards the end of incubation correlates with the time of appearance of lamellar bodies in the lung epithelial cells and of surfactant in the airways.

Animals↗

PubMed1981

Temperature-dependent and transformation-associated changes in polyamine metabolism in normal and Rous sarcoma virus-infected chick embryo fibroblasts.

Tertiary cultures of chick embryo fibroblasts infected and transformed by the wild-type Rous sarcoma virus, when actively growing at 35 degrees C, had higher putrescine levels than the respective uninfected cells. Transformed cells also had much higher specific activity of ornithine decarboxylase (EC 4.1.1.17) than the normal fibroblasts. At 41 degrees C the difference in putrescine levels between the normal and the transformed cells was less marked, and both cell types showed a relative accumulation of spermine. Cultures infected with the NY68 mutant virus, which is temperature-sensitive for transformation, showed at 41 degrees C normal cell morphology and intermediate polyamine patterns, while at 35 degrees C a transformed phenotype was found in both aspects. In shift-down experiments a change towards the permissive temperature pattern of polyamine metabolism was evident within 2-3 h. Difluoromethylornithine, a specific and irreversible inhibitor of ornithine decarboxylase efficiently reduced the enzyme activity as well as the levels of both putrescine and spermidine in all culture types and temperatures. Incubation of Rous sarcoma virus-transformed cells with 3 mM difluoromethylornithine for 36 h did not affect the maintenance of the transformed state. Likewise, when NY68-infected cultures were exposed to difluoromethylornithine at 41 degrees C for 12 h and then shifted down to 35 degrees C, the appearance of the transformed morphology took place concomitantly with that of the control cultures without respective changes in the polyamine levels. This suggests that the transformation-associated pattern of polyamines in chick embryo fibroblasts is not a prerequisite for morphological transformation of these cells.

Animals↗

PubMed1987

Response to antitumor agents of murine transplantable tumors implanted onto chorioallantoic membrane of chick embryo.

The chorioallantoic membrane of chick embryo was used to examine the chemosensitivity of the murine tumors, B16-F1 melanoma, B16-F10 melanoma, Meth-A fibrosarcoma, and Ehrlich carcinoma. The tumors were grown on the membrane, and the effects of 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride, cyclophosphamide, dacarbazine, 5-fluorouracil, methotrexate, adriamycin, mitomycin C, vincristine, and cisplatin on the growth of the tumors were tested by iv injection into a vein of the chorioallantoic membrane or injection into the yolk sac. The use of chick embryo limits the time for drug exposure to 3 or 4 days, but Ehrlich carcinoma and Meth-A fibrosarcoma needed longer for the test; the use of irradiation from a cobalt source overcame the problem by increasing the growth rate of the grafts of these two tumors. There appeared to be a good correlation between the effects of the drugs on B16 melanomas grown in the eggs and in the original animals. Many compounds, including pro-drugs such as cyclophosphamide and dacarbazine, could be assayed in this way.

Allantois↗

PubMed1976

Alterations in the ultrastructure of Chlamydia psittaci 6BC harvested from the allantoic fluid of chick embryos.

The allantoic fluid of chick embryos infected with Chlamydia psittaci is routinely used as a source of material for the study of the chemical and biological properties of the chlamydiae. We have examined pellets recovered from this allantoic fluid by low- and high-speed centrifugation, as well as high-speed pellets which had been stored at -70 degrees C, and we find that all of the pleomorphic forms of the chlamydiae are present in these materials. The reticulate bodies and large intermediate bodies are always seen to be morphologically damaged in that their cell envelopes are modified and in that they are distended and occasionally 'leaky.' No morphological evidence of damage was seen in small intermediate bodies or in elementary bodies in any of the materials which were examined. Thus the chlamydial population recovered from the allantoic fluid of infected chick embryos has been modified by selective damage to the least-condensed particles. We propose that the release of lysosomal enzymes from the host cell may coincide with the release of the chlamydia and that these enzymes may be responsible for this selective damage.

Allantois↗