Stages Of Chick Embryo Research Articles

The muscarinic receptor of chick embryo cells: correlation between ligand binding and calcium mobilization.

In this report we characterize muscarinic cholinergic receptor on embryonic cells. We established dose-response curves by fluorometric measurement of Ca2+ mobilization in cell suspensions of whole chick embryos stage 23/24. Ca2+ mobilization was quantitated by standardization of chlorotetracycline (CTC) fluorescence changes after stimulation with muscarinic agonists. We determined ED50 values for the agonists acetylcholine and carbachol as 3.4 X 10(-6) and 2.7 X 10(-5) M, respectively. Pilocarpine and oxotremorine were found to act as reversible competitive antagonists with inhibition constants (Kl) of 5.0 X 10(-6) and 1.4 X 10(-6) M, respectively. Bethanechol, which induced only 23% of the maximal effect obtained by acetylcholine, was a partial agonist with an ED50 of 4.8 X 10(-4) M. Its antagonistic component is expressed by an inhibition constant of 1.9 X 10(-4) M. In parallel, binding studies were performed in a competition assay with [3H]-quinuclidinylbenzilate. For the agonists acetylcholine and carbachol, binding parameters were best fitted by a "two binding-sites model." Comparison with dose-response curves indicated that Ca2+ mobilization was triggered via the high-affinity binding site. The inhibition constants of antagonists derived from the shift of dose-response curves corresponded to the fitted KD values of the binding studies when a "one binding-site model" was applied. Combination of dose-response and binding data showed close proportionality between receptor occupancy and calcium mobilization. No spare receptors were present.

Developmental profiles and properties of hepatic peroxisomal apo- and mitochondrial holoalanine:glyoxylate aminotransferase during chick embryogenesis.

Alanine:glyoxylate aminotransferase was present as the apoenzyme in the peroxisomes and as the holoenzyme in the mitochondria in chick embryos. The peroxisomal enzyme predominated in the early stage and gradually decreased during embryonic development and disappeared after hatching. In contrast, the mitochondrial enzyme gradually increased and predominated in the later stage of chick embryos. Peroxisomal alanine:glyoxylate aminotransferase in chick embryos was a single peptide with a molecular weight of about 40,000. The enzyme differed from the mitochondrial enzyme in the embryos, and mammalian alanine:glyoxylate aminotransferases 1 (with a molecular weight of about 80,000 with two identical subunits) and 2 (with a molecular weight of about 200,000 with four identical subunits) in molecular weights and immunological properties. Mitochondrial alanine:glyoxylate aminotransferase in chick embryos had an identical molecular weight and immunologically cross-reacted with mammalian mitochondrial alanine:glyoxylate aminotransferase 2. Pyridoxal 5'-phosphate dissociated easily from the peroxisomal enzyme saturated with pyridoxal 5'-phosphate. Hepatic aspartate:2-oxoglutarate aminotransferase and alanine:2-oxoglutarate aminotransferase in chick embryos, and hepatic alanine:glyoxylate aminotransferases in different animal species were all present as the holoenzyme.

Cephalic flexure formation in the chick embryo.

The cephalic flexure, found in all vertebrate brains, is a ventrally directed bend through the mesencephalon, and a ventral bulging and elongation of the prosencephalon. Most sources say the cephalic flexure is caused by differential growth. We have measured the changing angle of flexure through time and find that flexure occurs between chick embryo stages 10 to 15. We measured, during these stages, the lengths, thicknesses, and volumes of the floor and roof of the mesencephalon and of the prosencephalon. As expected, during flexure the mesencephalic roof elongates much more than the floor. Both roof and floor increase in thickness, and mesencephalic roof volume increases twice as much as floor volume. However, prosencephalon, which does not bend, also has differential growth between roof and floor, but the growth is taken up in complex changes of shape other than flexure. There are sufficient numbers of mitoses in the brain to account for the observed tissue growth, assuming accompanying cell enlargement. We deleted brain parts adjacent to the mesencephalon before flexure and the mesencephalon bent, so migration of cells from or to these adjacent parts to contribute to the differential growth of the mesencephalon is unlikely. We reduced cerebrospinal fluid pressure during flexure by explanting heads to the chorioallantoic membrane, or into New cultures. The mesencephalon of explanted heads bends, but the prosencephalon fails to elongate. We conclude that differential growth may be necessary for mesencephalic flexure in the chick embryo, but other factors that decide the disposition of the products of growth in space must determine the shape.

The myosin of developing chick embryo

Two components were present in myosin preparations from the early stage of chick embryo. The sedimentation coefficient ( s 20, w 0) were 3.4 and 6.7, respectively. The two components were separated with ammonium sulfate. Both components had ATPase activity of myosin type as rabbit myosin. The specific ATPase activity of the 6S component was higher than that of the 3S component but lower than that of adult myosin. Urea, 1–2 m, increased the ATPase activity of the 3S component but inhibited that of the 6S component. The interaction between the two components of embryonic myosin and adult actin were observed to occur at 0.6 m KCl as well as at lower ionic strength. Monomeric particles of each component were observed under an electron microscope by a shadow casting technique; their gross shape resembled that of rabbit myosin. Organized filaments of each component were formed at low ionic strength, only in the presence of ATP, but their shapes differed from each other. In the presence of 5 m guanidine-HCl both components of embryonic myosin showed a single sedimentation boundary. Based upon these observations a possible relationship between the two components of embryonic myosin is discussed.

Reversible effect of chloroacetophenone by sulphydryl groups on morphogenesis of chick embryos

ABSTRACT Chloroacetophenone (CAP), a specific inhibitor of SH groups, applied at 5 × 10−4 M for 15 min at the definitive primitive streak stage of chick embryos causes abnormalities, predominantly in the nervous system. The effects of CAP can be reversed by a subsequent treatment with thiomalic acid (5 × 10−4) or glutathione (1 × 10−5 M). Equimolar concentration of serine (4 × 10−4), which is structurally similar to cysteine except that SH of cysteine is replaced by OH in serine, fails to reverse the effects of CAP. The results of the present work suggest that the reversal of the CAP effects is brought about by SH groups.

Action of Triethanomelamine (TEM) on Early Stages of Chick Embryos

ABSTRACT Of many closely related compounds investigated recently from the point of view of cytotoxity and tumour-inhibiting properties 2,4,6-tri-(ethyleneimino)-1,3,5-triazine (called also triethanomelamine or TEM) proved to be the most effective substance against the Walker rat carcinoma. First descriptions of this fact were published in 1950 (Buckley et al. and Burchenal et al.). Also in 1950 appeared the publication of the first results of the clinical application of TEM at the First International Cancer Congress (Mueller & Miller). Later on Karnovsky et al. (1951) and Petersen et al. (1951) recommended procedures for parenteral and oral administration of this substance in clinical treatment. Very recently TEM has been introduced in a commercial form for oral and parenteral administration in cases of leukaemia, Hodgkin’s disease, polycythaemia vera, and other neoplastic conditions.

Regeneration in the hindbrain of neural tube stages of chick embryos.

The Anatomical RecordVolume 123, Issue 2 p. 169-181 Article Regeneration in the hindbrain of neural tube stages of chick embryos Bengt Källén, Bengt Källén Department of Zoology, Washington University, St. Louis, Missouri On leave from Tornbald Institute for Comparative Embryology, Lund, Sweden, on a Rockefeller Fellowship.Search for more papers by this author Bengt Källén, Bengt Källén Department of Zoology, Washington University, St. Louis, Missouri On leave from Tornbald Institute for Comparative Embryology, Lund, Sweden, on a Rockefeller Fellowship.Search for more papers by this author First published: October 1955 https://doi.org/10.1002/ar.1091230203Citations: 21 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume123, Issue2October 1955Pages 169-181 RelatedInformation

Further studies in modified mitosis

AbstractIn a paper published by the author in 1931 there was described a process of cell division called ‘modified mitosis.’ The present report adds quantitative studies of the process and a general evaluation of it and its role in the development of the embryo. Cell counts were made in various stages of chick embryos and the mitotic indices determined. In no cases can these mitotic indices account for the growth which the cell counts indicate. Periodicity in cell division in the chick cannot be established. Modified mitosis appears after careful study to be fundamentally mitotic in nature. Actual division of chromatin, nucleus, and cytoplasm occurs. Modified mitosis is not amitotic in character, but it is probable that it is what has been reported in the past as amitosis. It is very doubtful whether amitosis is found in the chick or in any of the vertebrates. Modified mitosis is part of the active phase of cell division and cannot be explained away as merely resting stages containing one or two nucleoli. It is probable that the division of chromatin nucleoli cannot be accounted for on any other basis than that of modified mitosis. In modified mitosis we undoubtedly see irreversible cell differentiation. The genetic implications of this process are not yet clear. If present interpretations of modified mitosis are in error a complete revision of our ideas of typical mitosis is in order.