SEARCH · PubMed Health

Results for “Chick Embryo”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources

PubMed1995

Straying phenomenon of migrating LHRH neurons and highly polysialylated NCAM in the chick embryo.

The present study on unilaterally incompletely placodectomized chick embryos revealed that arrival of migrating LHRH neurons into the forebrain area is dependent on the presence of a central projection of the olfactory nerve. When a fragment of the lateral and medial olfactory epithelium was spared the damage, a small number of LHRH-ir cells were found to migrate into the forebrain along a thin NCAM-H-expressing fiber bundle of the olfactory nerve. In embryos with large lesions which destroyed the lateral olfactory epithelium, the poorly developed NCAM-H-positive olfactory nerve fibers were arrested where they meet the NCAM-positive medial nasal branch of the ophthalmic nerve and frequently fused with this branch fiber bundle. In these embryos, no LHRH-ir cells were detected in the forebrain area. They were deviated from their regular migratory course to the NCAM-H-positive medial nasal branch fiber bundle. This straying phenomenon indicates that some structural support is apparently needed for the migration of LHRH-ir cells, but their migratory route is not completely programmed in their precursor cells in the olfactory placode. In cultures of placodal tissues, the coexistence of migrating LHRH-ir cells with NCAM-H-expressing neural elements was always confirmed. It is suggested therefore that not only the structural support for the migration but also the interaction between LHRH-ir cells and NCAM-H-expressing neural elements is a prerequisite for successful LHRH neuronal migration.

Animals↗

PubMed1988

Dynamics of functional maturation and inactivation of HN glycoprotein in NDV-infected chick embryo fibroblasts.

In avirulent NDV strain-infected chick embryo cells treated with cycloheximide at different intervals post infection a decrease of the level of hemagglutinating (HA) and neuraminidase (Nase) activities was observed. Studies on this system led to conclusion that the HA-Nase (HN) glycoprotein molecules are unstable and the actual amount of the functionally active (mature) HN entities is determined by a dynamic equilibrium between the antidromic processes of the HN functional maturation and inactivation. Kinetic studies on the actual intracellular levels of the HA and Nase activities using 5 min intervals of their detection after the cycloheximide treatment permitted to uncouple the processes of the HN maturation and inactivation. Analytical part of the studies made it possible to compute quantitative parameters of the involved processes: (a) pool size of the functionally nonactive HN precursors, (b) time needed for their functional maturation, and (c) rate of their inactivation.

Animals↗

PubMed1982

A survey of differences between membrane polypeptides of transformed and nontransformed chick embryo fibroblasts.

Plasma membrane-associated polypeptides of chick embryo fibroblasts and cells transformed by the Schmidt-Ruppin wild-type strain of Rous sarcoma virus and its temperature-sensitive tsNY68 mutant were compared by two-dimensional gel electrophoresis. Polypeptide and glycoprotein alterations were identified after incubation of cells with [35S]methionine and [3H]mannose and by staining of the gels with 125I-labeled concanavalin A and Coomassie brilliant blue. Polypeptides found to be consistently transformation-sensitive included a group of five polypeptides that were detected only by short-term labeling with methionine, fibronectin, a 180 kDa polypeptide with a pI of 5.6, a mannose-containing glycoprotein of 48 kDA and an unusually high pI of 8.4, and a 19 kDa polypeptide with a pI of approx. 4.5. Several of these polypeptides appear to be particularly interesting for further characterization.

Animals↗

PubMed1989

Electron microscopy of the pathology and chemotherapy of Legionella pneumophila infection in the chick embryo.

The ultrastructural pathology induced in organs of chick embryos previously infected with 100 times the yolk sac LD50 of Legionella pneumophila was examined by electron microscopy. Subtle pathological changes were observed three days post-inoculation while more extensive cellular and sub-cellular necrosis occurred at four days post-inoculation. Selected antimicrobial agents were administered three days after infection and evaluated for their ability to reduce or reverse ultrastructural lesions. In this study, ciprofloxacin was the only antibiotic that reversed tissue damage induced in response to infection with L. pneumophila while doxycycline, erythromycin, and rifampicin were also effective, but to a lesser degree. These results demonstrated the superior antimicrobial activity of ciprofloxacin and further illustrated the efficacy of the fertile hen's egg as a useful in vivo assay system for the evaluation at the ultrastructural level of putative chemotherapeutic agents for the treatment of Legionnaires' disease.

Animals↗

PubMed1973

Primer requirement and template specificity of a DNA polymerase of chick embryo.

A DNA polymerase purified from extracts of chick embryo catalyzes the synthesis of poly(dT) in the presence of poly(rA) or poly(dA) as template and poly(dT) or oligo(dT) as primer. Oligo- or polyribonucleotides are relatively ineffective initiators of polydeoxynucleotide polymerization. Using activated DNA as template, the enzyme catalyzes a repair-like reaction that resembles that catalyzed by RNA-directed DNA polymerase of RNA tumor viruses and Escherichia coli DNA polymerase II. With natural templates containing poly(rA) sequences, such as avian myeloblastosis virus RNA or rabbit globin mRNA, and oligo(dT) as initiator, principally poly(dT) is synthesized. Consequently, the enzyme differs from the RNA-directed DNA polymerase associated with RNA tumor viruses by its incapacity to transcribe heteropolymeric regions of RNA templates. The possible role of the enzyme in repair of DNA during transcription is discussed.

Adenine Nucleotides↗

PubMed1990

Role of corticosterone on the development of passive electrical properties of cultured chick embryo neurons.

We worked with neuronal cells of chick embryo cultures. The cells were obtained from 7 days-old embryos and cultured for 12 days. The experimental group was submitted to a single dose of corticosterone during the first 48 hours of culture. We measured the membrane resting potential at different external potassium concentrations, as well as the passive electrical properties of the membrane, resistance, time constant and capacitance. We found that the control cells develop progressively their potassium permeability and the electrical properties of the membrane until reaching values in this parameters that were similar to those found in adult cells. Corticosterone application induced a significant enhancement in these parameters in 3 and 6 days-old cultures as compared with the control cultures. These results suggest that glucocorticoids accelerate the differentiation process of the neurons in culture when applied at very early stages of development. We discuss the possible mechanisms involved in this action.

Animals↗

PubMed1984

The structural proteins of chick embryo lethal orphan virus (fowl adenovirus type 1).

Chick embryo lethal orphan (CELO) virus (fowl adenovirus type 1) contains at least 14 structural proteins with polypeptide molecular weights ranging from 100K to about 6K. A nomenclature of the CELO virion polypeptides is presented and the molar proportion of each polypeptide has been estimated. The CELO virus pentons were specifically released from the virion by dialysis against borate-based calcium-magnesium saline. The penton base (polypeptide III, mol. wt. 92K) and two fibres were separated, characterized and their polypeptides were correlated with their morphological positions in the virion. Peptide mapping suggested that the long fibre (polypeptide IV, mol. wt. 65K), and the short fibre (polypeptide VII, mol. wt. 44.5K) were not related in their primary sequences and are therefore probably encoded by separate genes. The time course of synthesis of the CELO virion polypeptides indicated that, like their mammalian adenovirus counterparts, they are synthesized late (after viral DNA replication).

Adenoviridae↗

PubMed1966

The hydrating effect of lathyrogenic compounds on chick-embryo cartilage in vivo.

1. Treatment of the chick embryo with the lathyrus factor, beta-aminopropionitrile, produces inhibition of polymerization of newly synthesized collagen at the interand intra-molecular level (Levene & Gross, 1959; Martin, Gross, Piez & Lewis, 1961); this is manifest as an increase in the fragility and solubility of collagen from the connective tissues. 2. This treatment simultaneously produced increased hydration of the tissues, particularly noticeable in the swollen long-bone cartilages. 3. This increased hydration of cartilage was found to result from treatment with any of the known lathyrogenic compounds, but not with any of the structurally related but non-lathyrogenic analogues. 4. The hydration effect paralleled the collagen solubility effect, both being dosage-dependent at the lower levels. 5. The hydration effect could not be reversed by treatment in vivo with either pyridoxal or glyceraldehyde, or by Benadryl, an antihistamine that inhibits cell water movement. 6. The possible causes of this effect have been considered in the light of the known properties of cartilage.

Aminopropionitrile↗

PubMed1987

Morphometric study of cartilage dynamics in the chick embryo tibia. I. Methodology and tissue compartments in normal embryos.

Cartilage dynamics during the development of the chick embryo tibia has been studied by means of morphometric methods, from the 11th to the 14th days. The volume densities of the structures enclosed by the perichondrium-periosteum did not change significantly through the age span studied, whereas the absolute volumes of these structures increased during the whole period under investigation. The cartilage volume showed the most rapid increase from Day 12 to Day 13 (by a factor of x1.74). The volume of the invading connective and vascular tissue increased rapidly from Day 11 to Day 14. The rate of cartilage formation decreased from 7.60 +/- 1.02 to 3.82 +/- 0.89 mm3/day (from Day 13 to Day 14), whereas the rate of cartilage resorption increased until Day 13 (by a factor of x2.71), reaching a plateau after this age. Although cartilage formation was higher than resorption during this period, the changes found by Day 13 indicate that shortly after this age cartilage resorption will predominate over cartilage formation, leading to the disappearance of the cartilaginous model.

Animals↗

PubMed2006

Epithelial transformations in the establishment of the blood-gas barrier in the developing chick embryo lung.

The tall epithelium of the developing chick embryo lung is converted to a squamous one, which participates in formation of the thin blood-gas barrier. We show that this conversion occurred through processes resembling exocrine secretion. Initially, cells formed intraluminal protrusions (aposomes), and then transcellular double membranes were established. Gaps between the membranes opened, thus, severing the aposome from the cell. Alternatively, aposomes were squeezed out by adjacent cells or were spontaneously constricted and extruded. As a third mechanism, formation and fusion of severed vesicles or vacuoles below the aposome and their fusion with the apicolateral plasma membrane resulted in severing of the aposome. The atria started to form by progressive epithelial attenuation and subsequent invasion of the surrounding mesenchyme at regions delineated by subepithelial alpha-smooth muscle actin-positive cells. Further epithelial attenuation was achieved by vacuolation; rupture of such vacuoles with resultant numerous microfolds and microvilli, which were abscised to accomplish a smooth squamous epithelium just before hatching.

Actins↗

PubMed1990

Fibronectin biosynthesis: influence on fibroblast adhesion during chick embryo development.

Eight d (8d) and 16d (16d) chick embryo fibroblasts (CEF) exhibited marked differences in their adhesive capacity on plastic support, but not on fibronectin substratum. This suggests differences in fibronectin (FN) expression and/or FN receptor expression. Both 8d and 16d CEF expressed an identical number of membrane receptors for FN with similar affinity. In contrast, the newly synthesized FN appeared de novo in 30 min in 8d CEF versus 60 min in 16d CEF. This difference is not due to a modification of the polypeptide chain biosynthetic rate. The FN synthesized in 8d CEF became insensitive to endo beta-N-acetyl-glucosaminidase H (endo H) treatment after 20 min, whereas it remained sensitive to endo H until 60 min in 16d CEF. Post-translational modifications of N-linked mannose-rich chains to complex type chain may account for the difference in the expression of cell surface FN and thus for the difference in cell adhesion capacity to plastic.

Animals↗

PubMed1988

Involvement of excitatory neurotransmitters in the damage produced in chick embryo retinas by anoxia and extracellular high potassium.

Chick embryo retinas were exposed for 40 min to anoxic conditions and the resulting histological changes were studied by light microscopy. A strong edematous response with severe swelling of the inner nuclear, inner plexiform and ganglion cell layers and numerous cells with pyknotic nuclei but very few dead cells were observed. These changes were qualitatively similar to those observed on retinas exposed to high potassium concentration or to glutamic acid. The deleterious effects of anoxia and high potassium concentration were not affected by the removal of calcium ions from the retina incubation medium but were prevented by gamma-D-glutamylglycine, an antagonist of excitatory amino acid receptors. These results suggest that the damage observed in retinas maintained under anoxia for 40 min is likely to be due to the release, from non-synaptic pools, of excitatory neurotransmitters, possibly glutamic and/or aspartic acids, evoked by the dissipation of the membrane ionic gradients. These events would be the first in a chain of toxic damage leading ultimately to cell death.

Animals↗

PubMed1989

[Biological evaluation of biomaterials using cultured chick embryo femurs (3)].

The biological effects of adhesive resins were studied by an organ culture method using chick embryo femurs, of which usefulness was investigated to evaluate the biocompatibility of biomaterials. Superbond C & B and Panavia EX were processed to form test pieces of 0.35 mm in diameter and 2 mm in length. The test piece was inserted into the distal epiphysis of the femur, which was cultured at 37 degrees C for 7 days. The biomaterials were evaluated by relative growth rate, relative wet/dry weight ratio (W/D) and histological examination. The femurs with insertion of Superbond C & B or Panavia EX did not show growth inhibition, but W/D of Panavia EX was significantly higher than that of control. Histologically, undifferentiated cartilage cells and immature cartilage matrix were observed in the tissue adjacent to Panavia EX. These results suggested that Panavia EX had a slightly toxic effect on the chick embryo femur.

Animals↗

PubMed2002

Developmental changes of HT7 expression in the microvessels of the chick embryo brain.

The neurothelin/HT7 antigen is a chick-specific, cell-surface glycoprotein expressed by the brain endothelial cells and widely utilized in experimental studies as a marker of barrier-provided vessels. Previous immunohistochemical studies have demonstrated that HT7 is already expressed in the embryonic brain vessels and that it is first detectable on embryonic day 10 and developmentally regulated. In the present study, the vascular expression of HT7 was investigated in different regions of the central nervous system from the 5th day right up to the latest stage of the chick embryo development. The study was carried out utilizing a monoclonal antibody anti-HT7, which was detected by both enzymatic and fluorescent immunohistochemical methods. The observations demonstrated the presence of HT7-stained vessels as early as embryonic day 6 in the rhombencephalon and mesencephalon, and at embryonic day 9 in the prosencephalon. Regional differences were also evidenced within the rhombencephalon and mesencephalon, since the endothelial antigen HT7 was expressed earlier in the brain stem (tegmentum of the medulla oblongata, pons and mesencephalon) than in the cerebellum and optic tectum. The caudo-cranial and ventro-dorsal gradients of HT7 expression were temporally and spatially related to the development of the brain vessels. The early detection of HT7 staining in the choroid plexus epithelium and perineural vessel endothelium, sites of the blood-cerebrospinal fluid barrier and pial barrier, respectively, has confirmed this antigen to be a precocious marker for all the barrier systems in the brain.

Animals↗

PubMed1992

Image analysis of the lens opacities induced in developing chick embryo by glucocorticoid.

Glucocorticoid-induced cataracts in chick embryos were monitored by an image analysis system. Opacities in the lens visually showed a complex pattern with significant changes in the cortical and nuclear regions. An electronic image analyser produced an image in which contrast represented different zones of lens opacification in the frontal plane and documented objective lens findings such as the precise topography of the opacities, density and opacity measurements, geometric measurements of boundary surfaces and of regional areas. Parameters of lens clouding were evaluated quantitatively by measuring the optical density index and the area of the zones of clouding outlined with equi-densities. The light intensity standard graded different morphological areas of the lens into up to 256 grey levels. The data were entered and stored quantitatively into a computer. The lens images thus picked up by the TV camera and digitally stored in a frame buffer of the measuring system could be reliably transformed into a 2-D or 3-D picture of lens clouding. The approach demonstrated by the current study provides a sensitive and meaningful measure of cataractous changes for lens laboratory research.

Animals↗

PubMed1991

Developmental changes in the type I procollagen processing pathway in chick-embryo cornea.

Type I procollagen processing in chick-embryo corneas was studied at days 12, 14 and 17 of development. Pulse-chase experiments and electrophoretic analysis of salt-soluble extracts showed developmental changes in the processing pathway. A kinetic model was fitted to the data to determine rate constants for processing of both N- and C-propeptides. Data for pro alpha 1(I)-chain processing and pro alpha 2(I)-chain processing were fitted separately (where pro means procollagen). Between days 12 and 17 the relative flux through the pC-collagen (procollagen chain lacking the N-propeptide) and pN-collagen (procollagen chain lacking the C-propeptide) pathways increased approx. 4-fold. Pro alpha 1(I) chains and pro alpha 2(I) chains were processed by slightly different routes. Variations in the rate constants were compared with electron-microscopic measurements of collagen fibril diameters at each stage of development. Diameters increased by less than 10% over the period from 12 to 17 days. It was concluded that fibril diameters are relatively insensitive to the pathway of procollagen processing in the salt-soluble pool.

Animals↗

PubMed2001

Cell interactions underlying notochord induction and formation in the chick embryo.

The development of the notochord in the chick is traditionally associated with Hensen's node (the avian equivalent of the organizer). However, recent evidence has shown that two areas outside the node (called the inducer and responder) are capable of interacting after ablation of Hensen's node to form a notochord. It was not clear from these studies what effect (if any) signals from these areas had on normal notochord formation. A third area, the postnodal region, may also contribute to notochord formation, although this has also been questioned. Using transection and grafting experiments, we have evaluated the timing and cellular interactions involved in notochord induction and formation in the chick embryo. Our results indicate that the rostral primitive streak, including the node, is not required for formation of the notochord in rostral blastoderm isolates transected at stages 3a/b. In addition, neither the postnodal region nor the inducer is required for the induction and formation of the most rostral notochordal cells. However, inclusion of the inducer results in considerable elongation of the notochord in this experimental paradigm. Our results also demonstrate that the responder per se is not required for notochord formation, provided that at least the inducer and postnodal region are present, although in the absence of the responder, formation of the notochord occurs far less frequently. We also show that the node is not specified to form notochord until stage 4 and concomitant with this, the inducer loses its ability to induce notochord from the responder. The coincident timing of these changes in the node and inducer suggests that notochord specification and the activity of the inducer are regulated through a negative feedback loop. We propose a model relating our results to the induction of head and trunk organizer activity in the node.

Animals↗

PubMed1992

Changes in the ribonucleoprotein constituents of the nucleus during the differentiation of muscle cells in the chick embryo.

The ribonucleoprotein components of the nucleus of chick embryo muscle cells in different stages of development were studied by electron microscopic quantitative stereology. The changes of the constituents were related with the appearance of the innervation by means of silver impregnation for light microscope. The numerical density of the perichromatin granules (PCG) is low in mononuclear cells and myotubes. It is noteworthy that the frequency of the PCG does not change during the transition of the cells in mitotic cycle to postmitotic myoblasts and during myofibril differentiation. However, there is an important increment in this parameter when the motor nerve fibers arrive at the muscle and the synaptic contacts are established. This change is correlated with appearance, or at least with a great increase, of the importance of posttranscriptional controls of the expression of some genes. The augmentation in the frequency of PCG is not accompanied by alterations of the abundance of total RNP particles, in close resemblance with the phenomena occurring in neuroblast during the differentiation of synaptic endings. The variations of the nucleolar volume coincide with the changes in rRNA synthesis.

Animals↗