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PubMed1976

Skeletal malformations induced by mitomycin C in chick embryos.

One hundred and eighty chick embryos were studied for the presence of skeletal malformations after administration of mitomycin C at 72, 96 and 120 hours of incubation. Axial skeleton defects included those of ribs, vertebrae, beak and crania. Appendicular skeletal defects were mainly confined to the lower limbs e.g. absence of phalanges, bent and shortened femur, fibula, tibia and metatarsus, in that order. Absence of phalanges and curved scapulae were noted in the upper limbs. The length of femur, tibia and metatarsus was significantly reduced (P less than 0.001) compared with the corresponding controls especially in the group treated at 96 h.

Abnormalities, Drug-Induced↗

PubMed1989

Purification of an autocrine growth factor in conditioned medium obtained from primary cultures of scleral fibroblasts of the chick embryo.

Scleral fibroblasts of the chick embryo were found to secrete autocrine growth factors. One of the factors was purified from conditioned medium collected from growing-phase cultures of these cells by DEAE-Sepharose column chromatography and following non-denaturing polyacrylamide gel electrophoresis. The specific activity was increased 1100-fold by this purification. The chromatographically purified growth factor was still active after incubation at 95 degrees C, at pH 10 or pH 3, or with glycosidase H, but inactive after incubation with dithiothreitol or trypsin. An active protein having a molecular weight of 32 kDa was found to be the major component of the final preparation.

Animals↗

PubMed1984

The threshold quantity of nerve required to induce limb regeneration in the chick embryo.

Wingbuds of 4-day chick embryos were amputated at the future elbow joint and a segment of embryonic neural tube was implanted longitudinally in the stump. The cross-sectional area and number of nerve bundles were determined in limbs in which limb regeneration occurred and compared with similar measurements in control limbs without neural tube implant. The number of nerve bundles in regenerated limbs was not significantly greater than in control limbs which did not regenerate. However, the cross-sectional area of nerve bundles was significantly greater in the limbs that had undergone regeneration. The data support the view that the amount of axoplasm available at the amputation (surface) site is the essential factor in determining the success or failure of regeneration.

Animals↗

PubMed1980

[Angiographic examinations of the circulatory development of living chick embryos (author's transl)].

In chick embryos of an age of incubation of 5-14 days, the physiological development of the circulation and the morphological differentiation of the arterial system were studied by intravital and postmortal angiography. For the examinations of the living embryos, a special radiographic and injection technique had to be developed. The contrast medium was injected into the umbilical veins and transported by the actions of the embryonic heart. Continuous ECG recordings showed no marked interference of the injections with the cardiac activity. According to the angiographic findings, the circulation is relatively fast within the main arteries, but the capillary perfusion is prolonged and lasts up to several minutes. The average circulatory velocity of the blood stream within the carotid artery increases parallel to the arterial enlargement, whereas the circulatory time decreases and the number of heart beats during the period of carotid opacification does not change to a great extent. By this, a steady transport of gas and nutritional material may be achieved in the growing arterial system.

Angiography↗

PubMed1976

[Growth of eye and orbit in chick embryo. IX. Developement of eye and skull origin in 3-9 day old embryos with experimental bilateral microphthalmia].

Chick embryos in which on the third day of incubation the lens of both eye primordia was removed, were sacrificed at the ages of 5,7 and 9 days and fixed in a 70 per cent alcohol solution. An analysis was made of the consequences of the absence of normal large eyes upon the structure and growth of the skull. Immediately after the operation no changes in the head mesenchyme could be observed, but during the next days, as growth goes on, abnormal proportions and dimensions develop in the anterior part of the skull. Generally, this part of the skull is depressed and shorter than normal; cartilages around the eye have a different position and smaller dimensions. A perfect symmetry is only rarely maintained. There seems to be a very labile balance in the skull, as may be deduced from the presence of a buckled interorbital septum and the deviation of the upper beak.

Animals↗

PubMed1987

Scanning electron microscopy of the aggregation of head mesoderm cells from chick embryos.

Head mesoderm cells from chick embryos at different stages of development were dissociated and cultured on plastic coverslips. In all cultures several cellular aggregates were described by means of scanning electron microscopy. Isolated cells present filopodia and lamellipodia. However, when mesoderm cells make contact with one another the filopodial and lamellipodial activity in the contact cellular edge disappear. Thus, the cells into cellular clusters do not present projections. The clusters were circular and bidimensional in character. The scanning electron microscopic observations showed that it is the type 1 variant of "contact inhibition of locomotion" which occurs. By means of these mechanisms the bidimensional aggregates are formed and cellular overlapping is not present. Since the behaviour of the mesoderm cells "in vitro" in some way could be comparable to their behaviour "in situ", the results here observed are discussed in relation to the conduct of mesoderm cells "in vivo".

Animals↗

PubMed1987

Vitamin K1 amplification of benzo(a)pyrene metabolism in chick embryos.

Seventeen-day-old chick embryos were used as a test system to assess the effect of vitamin K1(K1) on benzo(a)pyrene (BP) metabolism as measured by the induction of arylhydrocarbon hydroxylase (AHH) and cytochrome P-450 and the levels of glutathione (GSH) and glutathione S-transferase (GST) in liver. Twenty-four hours after injection of BP into the air sac there was a sharp rise in AHH and P-450 and a drop in GSH. When K1 was injected 24 hr prior to BP there was a decrease in GST activity as compared with the control plus an augmented increase in AHH induction. This augmentation in BP metabolism (Phase I) together with a concomitant decrease in at least one mechanism of Phase II conjugation is in keeping with other evidence that K1 can play an adjuvant role in BP induced mutagenicity and carcinogenicity. Ubiquinone has a much lesser effect on BP metabolism than does K1 in equimolar concentration.

Animals↗

PubMed1993

Hemodynamic parameters of stage 20 to stage 35 chick embryo.

Hemodynamic parameters of the chick embryo from stage 20 (3 d of a 21-d incubation) up to stage 35 (8 d) are described. Normal values of dorsal aortic flow velocity wave forms were measured with a 20-MHz directional-pulsed Doppler velocity meter that was validated to be accurate above 5 mm/s. An analysis of variance was carried out for each of the flow velocity parameters. The correlation coefficient that represents the reproducibility was satisfactory (r > 0.90). There was a 17-fold rise in mean dorsal aortic blood flow (mm3/s). Heart rate doubled from 123 +/- 12 to 239 +/- 8 bpm, and stroke volume increased from 0.14 +/- 0.08 to 1.28 +/- 0.55 mm3. A stage-related rise was seen in peak systolic and mean velocities and peak acceleration. These data may serve as a basis for flow velocity wave form investigation and interpretation in developmental stages of cardiac malformations.

Animals↗

PubMed1971

Kinetic analysis of insulin action on amino acid uptake by isolated chick embryo heart cells.

1. Isolated chick embryo heart cells were used to investigate the mode of action of insulin on the transport of three naturally occurring amino acids: l-proline, l-serine and glycine. Initial velocities of uptake were measured over a period of 5min with an 80-fold range of amino acid concentration. Corrections for amino acid diffusion, incorporation into protein and conversion into carbon dioxide were introduced. 2. The uptake processes approximated Michaelis-Menten kinetics within definite ranges of amino acid concentrations. A single transport system for proline and at least two transport systems for serine and glycine were detected. 3. The kinetic effects of insulin on transport systems for the amino acids tested were consistent with an acceleration of the maximal velocity of the process, without substantial changes in substrate concentration for half-maximal transport velocity. 4. These hormonal effects were not essentially altered by the corrections for amino acid incorporation into protein and conversion into carbon dioxide.

Amino Acids↗

PubMed1980

[Scanning electron microscopy of the chick embryo mesonephros].

The mesonephros of chick embryos from the 7th to the 15th day of incubation has been studied by scanning electron microscope. The material was submitted to the common techniques for scanning electron microscopy using a special fixing agent that does not damage the embryonic tissue (Litke e Low, 1977). At the 7th day of incubation, the mesonephric corpuscles show a capsule whose parietal lamina is formed by flattened cells, while the visceral lamina already shows podocytes provided with pedicels interdigitating around the capillary loops. In the same period the proximal tubules appear to be bounded by columnar cells with long and thick apical microvilli. The Henle's loop is lined by low cells with slightly dome-shaped apices provided with single cilium. The distal convoluted tubules are lined by a low columnar epithelium. The cell apices show microvilli shorter and more rare than those found in the proximal portion. This pattern is present till the 12th day of incubation, when regression phenomena occur. These are mainly represented by a progressive occlusion of the tubules and a gradual alteration of the podocytes.

Animals↗

PubMed1994

The esterification of cholesterol in the liver of the chick embryo.

The development of the chick embryo was characterised by the accumulation of large droplets of lipid in the cytoplasm of the embryonic liver, as revealed by electron microscopy. Analysis of the lipid composition of the livers indicated that this accumulation resulted from a dramatic increase in the cholesteryl ester content of the tissue during the the latter part of the embryonic period. This lipid is apparently derived from yolk cholesterol and may be taken up by the liver in the form of lipoprotein remnants. Significant levels of acyl-CoA: cholesterol acyltransferase (ACAT) activity were expressed in the liver throughout the second half of the developmental period, and this activity was maximal at the time when lipid transfer from the yolk was most intensive. The activity of microsomal cholesterol ester hydrolase (CEH) was very low throughout development, and no CEH activity was detected in the cytosolic fraction. In addition, substantial amounts of a cytosolic protein which inhibits CEH activity were present. Thus the relative activities of these enzymic systems are consistent with the net accumulation of cholesteryl ester which occurs in the liver during development.

Animals↗

PubMed1990

Action of estradiol on müllerian duct regression induced by treatment with norethindrone of female chick embryos.

Treatment of genetically female chick embryos with norethindrone (NET), a progesterone-like steroid chemically related to testosterone, caused two types of Müllerian duct (MD) deficiencies. The first consisted in an absence of the caudal part of the ducts owing to their partial agenesia occurring between Days 5 and 7 of embryonic life. This is nonspecific since it was observed after a treatment with almost all steroidal sex hormones. In particular, this was obtained with estradiol which also increases the frequency and extent of agenesia caused by the NET, as reported here. The second type of deficiency appeared between Days 12 and 14 and was due to a regression destroying the more or less large part of the MDs having escaped agenesia, i.e., for most of the cephalic half. This resulted from the influence of the anti-Müllerian hormone originating from the ovary and normally inhibited by the ovarian estrogens. This protective action of endogenous estrogens was inhibited by the NET, but an additional treatment with estradiol removed this inhibition and prevented duct regression. Our results suggest that estrogen protects the duct from the regression induced indirectly by NET, by acting both at gonad and MD levels.

Animals↗

PubMed1985

Induction of thermotolerance and heat shock protein synthesis in normal and respiration-deficient chick embryo fibroblasts.

Normal and transformed chick embryo cells and their respective ethidium bromide-treated derivatives that are devoid of a functional respiratory chain were comparatively evaluated for their responses to hyperthermia treatment. No significant difference was found between the control and the respiration-deficient cells. The cells have a similar intrinsic thermosensitivity as judged by their capacity to form colonies after treatment at supraoptimal temperatures, and heat triggers in both cases an equal production of heat shock proteins and a strong induction of thermotolerance. In addition, sodium arsenite, carbonyl cyanide m-chlorophenylhydrazone, oligomycin, and antimycin A induce a similar heat shock protein response in the control and the treated cells. Based on these results, it is concluded that the inhibition by heat of the mitochondrial energy production does not constitute an obligatory rate-limiting event in hyperthermic cell killing and that the intracellular signal triggering development of thermotolerance or heat shock protein production does not obligatorily originate from damages to the respiratory chain. Moreover, the results indicate that the modifications responsible for the increased heat resistance of thermotolerant cells may not, or do not necessarily, involve a stabilization of the mitochondrial energy production.

Animals↗

PubMed1985

Effect of influenza virus on protein phosphorylation in isolated membranes of chick embryo cells.

Membranes isolated from chick embryo cells (CEC) were found to contain an endogenous protein kinase that phosphorylated endogenous proteins. 32P incorporation into membrane proteins was analysed by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and detected by autoradiography. Membrane phosphorylation in the presence of physiological saline (PM-phys) and in the presence of influenza virus (PM-V) were compared. Under short-time incubation (less than 1 min) with gamma-32P ATP there was practically no difference between PM-phys and PM-V in 32P incorporation. Under prolonged incubation (3-15 min), gradual dephosphorylation of the phosphoprotein moving in SDS-PAGE in the zone of relative molecular mass (Mr) of 60 kDa (phosphoprotein P60) was observed in PM-phys whereas in PM-V, phosphorylation of P60 increased with the time of incubation with gamma-32P ATP. Dephosphorylation of P60 in PM-phys was inhibited by 2.5 mmol/l EGTA as well as by 100 mumol/l chlorpromazine (CPZ) and stimulated by calmodulin (CaM) in the presence of Ca2+. Responsible for the dephosphorylation was probably the endogenous Ca2+ and/or CaM-dependent membrane protein phosphatase. It was inhibited by influenza virus (even in the presence of Ca2+ and CaM). The possible role of P60 phosphorylation in the first step of virus infection is discussed.

Animals↗

PubMed1988

B cell precursors in chick embryos surgically bursectomized at 72 h of incubation.

To determine the presence of precursor B cells in chick embryos surgically bursectomized at 72 h of incubation (E-Bx) we studied chick chimeras that were produced by establishing parabiotic connections between blood vessels of chorioallantoic membranes of normal and surgically bursectomized chick embryos. Using sex chromosomes and a B cell alloantigen (Bu-1a) as markers we showed that chick embryos bursectomized at 72 h of incubation contain B cell precursors capable of colonizing the bursa of Fabricius and developing into B lymphocytes. The repopulation capacity of 14-day-old embryonic spleen cells from E-Bx recipients was tested by transferring them into age-matched X-irradiated Bu-1-disparate embryos. The results show that B cell precursors are present in 14-day spleen of chick embryos bursectomized at 72 h of incubation. These precursors carry the Bu-1 B cell alloantigen, suggesting that commitment to the B cell lineage can take place in the absence of bursa.

Age Factors↗

PubMed1972

The structure of ribosomes as indicated by studies of tetramers from hypothermic chick embryos.

Ribosome tetramers induced in chick embryos by exposure to cold, and tetramers of large subunits derived from them, have been studied by electron microscopy and sucrose-density-gradient analysis. Individual ribosomes of the normal tetramer are elongated bean-shaped structures, 220-280A by 195A (1A=10(-1)nm) with a cleft in the outer edge which divides the two-dimensional image into two unequal ends. Most of the tetramers appear to attach to the surface of the electron-microscope grid by one preferred face. The subunits of the large-subunit tetramers have a round outline and no cleft. About 25% of the subunits of these tetramers have a line running radially across the particle. The dissociation of tetramers into large-subunit tetramers and small subunits has been shown to be reversible. Mixtures of these particles from sucrose-density-gradient fractions were reassociated to give a tetramer with the same sedimentation coefficient as the original tetramer and with the same structure as viewed in the electron microscope. The results indicate that the cleft is a property of the complete ribosome, and that it marks the position of the small subunit. The reversibility of the dissociation also strengthens the view that no change in the large subunit occurs during dissociation or reassociation, i.e. that the sites of interaction between ribosomes in both types of tetramer are the same. The conclusions affect the interpretation of electron-micrograph images and an anomaly in the relationship between the two types of tetramer is discussed.

Animals↗

PubMed1980

Secretion of chondroitin SO4 by monolayer cultures of chick embryo chondrocytes.

Monolayer cultures of chick embryo tibial chondrocytes incorporate 35SO42- into chondroitin SO4 which is rapidly secreted from the cells into two extracellular pools. Part of the extracellular chondroitin SO4 is recovered in a soluble form in the culture medium, and the remainder is associated with the cell matrix from which it is released by isotonic trypsinization. At 38 degrees C labeled chondroitin SO4 appears in the cell matrix fraction within 5 min after addition of 35SO42- and in the culture medium fraction 15 min after 35SO42- is added. The intracellular pool of labeled chondroitin SO4 reaches a steady state level of 150 to 200 pmol of bound SO4 per 10(6) cells in 60 min, while the cell matrix and medium fractions increase at rates of 3 and 1 nmol of bound SO4 per h per 10(6) cells, respectively. After 4 h of labeling, less than 20% of the newly synthesized cell-associated chondroitin SO4 is in the intracellular fraction. By labeling cells for 15 min at 25 degrees C 80% of the cell-associated chondroitin 35SO4 is obtained in the intracellular fraction. This material is chased without lag into both the cell matrix fraction and the medium fraction. A mixture of NaF and NaCN, both at 30 mM, lowers the cellular ATP level to 15% of normal and blocks secretion of the intracellular chondroitin SO4 into both extracellular fractions. Colchicine at 10(-6) M gives a partial inhibition of both synthesis and secretion of chondroitinSO4. Sucrose density gradient sedimentation analysis of the intracellular chondroitin SO4 and the two extracellular fractions shows that all three fractions contain both a heavy and light proteoglycan fraction. The intracellular light proteoglycan fraction is secreted preferentially into the culture medium where it represents 30% of the total culture medium pool. The ratio of 6-sulfated GalNAc to 4-sulfated GalNAc in the heavy proteochondroitin SO4 fraction is approximately twice that found for the light fraction.

Animals↗

PubMed1976

Uptake and metabolism of fatty acids and analogues by cultured cardiac cells from chick embryo.

Cultured heart cells from chick embryo, present as a confluent monolayer in a minimal medium, take up labelled fatty acids (from C6 to C22) bound to serum albumin with a rapid incorporation into neutral and complex lipids (visible at 15 s), while beta-oxidation is delayed (visible at 15 min). Fatty acids enter the cardiac cells through two mechanisms, one involving a readily saturable process, the other resembling passive diffusion. The saturable transport system recognizes fatty acids with a high affinity, Km from 4.5 to 16 muM. The V is from 0.03 to 0.3 nmol of fatty acid incorporated min-1 (10(6) cells)-1. Competitive inhibition occurs between fatty acids while glucose, aminoacids and lactate do not compete with palmitate for the entry into the cells. The analysis of unesterified fatty acids from the usual culture medium and from the cells show a gradient of concentration up to 54-fold; moreover experiments performed in minimal medium at 20 degrees C show that fatty acids accumulate up to 28-fold in the cells. Efflux rates can be measured after loading the cells at 20 degrees C; the curves are bimodal and the pseudo first-order rate constants thus determined are in the order of 0.5 min-1, as opposed to 2.5 to 5.0 min-1 for the passive-diffusion component calculated for the influx rates. Studies on the role of serum albumin at constant and at variable fatty acid-albumin molar ratios indicate that the rate of uptake is controlled by the total fatty acid concentration and not solely by the concentration of unbound fatty acids. No labelled fatty acid was found to be bound to the cytoplasmic fraction supposed to contain the fatty acids-binding protein; our results are in favour of the presence of a specific transport system for fatty acids either at the level of subcellular organelles or more likely at the surface of cardiac cells.

Animals↗