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Chick ex ovo Culture and ex ovo CAM Assay: How it Really Works

Biology

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Summary

The chick chorioallantoic membrane (CAM) is a unique, naturally immunodeficient supportive culture environment to study angiogenesis and tumorigenesis. This video article demonstrates the different steps in chick ex ovo culture, application of potentially angiogenic substances and successful inoculation of tumor cells and tissues on the surface of the CAM.

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Dohle, D. S., Pasa, S. D., Gustmann, S., Laub, M., Wissler, J. H., Jennissen, H. P., Dünker, N. Chick ex ovo Culture and ex ovo CAM Assay: How it Really Works. J. Vis. Exp. (33), e1620, doi:10.3791/1620 (2009).

Abstract

Chicken eggs in the early phase of breeding are between in vitro and in vivo systems and provide a vascular test environment not only to study angiogenesis but also to study tumorigenesis. After the chick chorioallantoic membrane (CAM) has developed, its blood vessel network can be easily accessed, manipulated and observed and therefore provides an optimal setting for angiogenesis assays. Since the lymphoid system is not fully developed until late stages of incubation, the chick embryo serves as a naturally immunodeficient host capable of sustaining grafted tissues and cells without species-specific restrictions. In addition to nurturing developing allo- and xenografts, the CAM blood vessel network provides a uniquely supportive environment for tumor cell intravasation, dissemination, and vascular arrest and a repository where arrested cells extravasate to form micro metastatic foci.

For experimental purposes, in most of the recent studies the CAM was exposed by cutting a window through the egg shell and experiments were carried out in ovo, resulting in significant limitations in the accessibility of the CAM and possibilities for observation and photo documentation of effects. When shell-less cultures of the chick embryo were used1-4, no experimental details were provided and, if published at all, the survival rates of these cultures were low. We refined the method of ex ovo culture of chick embryos significantly by introducing a rationally controlled extrusion of the egg content. These ex ovo cultures enhance the accessibility of the CAM and chick embryo, enabling easy in vivo documentation of effects and facilitating experimental manipulation of the embryo. This allows the successful application to a large number of scientific questions: (1) As an improved angiogenesis assay5,6, (2) an experimental set up for facilitated injections in the vitreous of the chick embryo eye7-9, (3) as a test environment for dissemination and intravasation of dispersed tumor cells from established cell lines inoculated on the CAM10-12, (4) as an improved sustaining system for successful transplantation and culture of limb buds of chicken and mice13 as well as (5) for grafting, propagation, and re-grafting of solid primary tumor tissue obtained from biopsies on the surface of the CAM14.

In this video article we describe the establishment of a refined chick ex ovo culture and CAM assay with survival rates over 50%. Besides we provide a step by step demonstration of the successful application of the ex ovo culture for a large number of scientific applications.


Daniel S. Dohle, Susanne D. Pasa, and Sebastian Gustmann contributed equally to this study.

Protocol

All equipment and reagents have to be purchased sterile or needs to be heat or steam sterilized or sterilized with 70% ETOH.

The authors state that experiments on animals were performed in accordance with the European Communities Council Directive (86/609/EEC), following the Guidelines of the NIH regarding the care and use of animals for experimental procedures and the regulations set forth by the Institutional Animal Care and Use Committee (IACUC) at the University of Duisburg-Essen (Germany).

Part 1: Incubation of eggs

  1. Fertilized eggs can be stored at 13°C for up to one week.
  2. Eggs are incubated for 72 hours, lying horizontally in an incubator with a moving tray, rotating the eggs 12 times a day continuously. Humidity is kept at 60 - 62%, incubation temperature at 37.5°C.
    Note: Before starting incubation, dirt, feathers and excrement are carefully removed from the egg shells mechanically by dry wiping with common, gray zigzag hand paper towels, which have a rough rather than a soft surface structure. Wiping the eggs with ethanol or disinfectant, however, significantly reduced survival rate of the embryos, irrespective of the liquid used.

Part 2: Ex ovo culture

  1. After incubation for 72 hours, eggs are removed from the incubator.
    Note: The eggs are incubated for 72 hours because - according to our experiments - for unknown reasons but in agreement with Auerbach et al.1 earlier development stages had significantly lower survival rates. At stages later than 72 hours the yolk sack which is not yet covered by the CAM becomes thinner and tends to adhere to the egg shell leading (i) to small haemorrhages at the area of adherence and (ii) the rupture of the yolk-sack membrane. Therefore the presented method is not applicable to embryos older than 72 hours.
  2. The top side of the eggs, where the embryo resides, is marked by pencil since the embryo resists rotation to a certain extent.
  3. The egg is held horizontally with the pencil mark on top and cracked on the edge of an 80 mm triangular magnetic stir bar laying oriented perpendicular to the long axis of the egg.
    Note: For a better feeling, no gloves should be used, but hands should be disinfected with 70% EtOH. It is important that the egg shell as well as the egg membrane are opened up. Leaking of egg white is a safe sign that the egg membrane has been perforated.
  4. The egg is kept close to the bottom of the Petri dish to avoid further leakage of egg white.
    Note: During the initial opening procedure, it is important that the egg white on the bottom of the Petri dish is still connected to the rest inside the egg as this results in a vacuum inside the egg which holds the yolk with the embryo on top inside the egg. The vacuum can be regulated either by finger pressure which controls the inlet of air into the egg or by lifting the egg which increases the column of connected egg white i.e. the vacuum.
  5. By gently applying pressure to the meridian running through the crack and equator of the egg by thumb and middle fingers it is possible to regulate the vacuum. The content of the egg can then be transferred to the Petri dish undamaged, if the egg with the yolk is gently lifted and both halves of the shell are carefully separated. The embryo and the yolk vessels should lie on top of an undamaged yolk.
    Note: If the pencil mark is not kept on top, the embryo might be hurt when cracking the shell. If the eggs are not cracked carefully enough or the embryos are older than 72 hours (see above), the yolk sack sticks to the shell and often ruptures. The same happens when the humidity of the incubator is lower than 60% or eggs are not rotated during incubation.
  6. Ex ovo cultures are returned to an incubator and kept at 37.5° 38.2°C and 60% humidity. CO2 or O2 supply is not necessary if the incubator is not closed hermetically (ventilation grid partially open!) and special Petri dishes with spacers between lid and dish are used.
    Note: Moving of the embryos should be kept to a minimum during the first days of incubation. Too much agitation results in high mortality rates. From incubation day 9 onwards, the embryos are less sensitive to agitation.
    Dead embryos should be removed immediately to avoid infections.
    If cell culture incubators are used, which are hermetically closed, O2 supply is mandatory for the embryos not to die. Humidity is essential for the CAM not to dry out and if incubation temperature is lower than 37°C, the embryos will develop too slowly.

Part 3: Application of substances for angiogenesis assays

  1. Autoclaved folded filter papers (5.5 mm in diameter) are punched by a hole puncher and used as supporting material (carrier) for liquid substances applied to the CAM.
    Note: Nearly each carrier material (see Table below) caused irritation of the CAM, especially when applied before incubation day 10, as it changed the developing CAM vessel architecture. This also included potentially inert substances like hydroxyethyl cellulose foil, Teflon sponges (PTFE-pledgets), collagen sponges, collagen foil, sterile gauze (swabs), round cover slips, and silicon rings, which all caused false positive results. Filter paper seemed to cause the least irritation and was therefore used in our assays.
  2. When the CAM is fully developed, up to 6 different samples may be applied and their effects can be compared on a single CAM.
  3. To avoid drying filters additional doses (3 μg native angiotropin) or buffer (5 μl PBS) should be re-applied every day.
  4. From day 3 after application, blood vessels orientate towards the angiogenic substances on the filters, whereas the pattern of blood vessels surrounding controls is unchanged.
    Note: The CAM should not be mistaken for the yolk-sack. The CAM is a dynamic developing structure while the yolk sack is static with little variances during development. On developing day three the developing CAM can be recognized for the first time at the caudal end of the embryo as a small vesicle. Between day three and day ten the initial vesicle expands, creating a folded two-layered membrane overgrowing the yolk sack at an increasing rate. The application site should be half way between embryo and the fold of the CAM (border) as otherwise the embryo hinders microscopic observation of effects in transmitted light. Alternatively, the filter with the angiogenic substance is internalized when the CAM keeps growing.

Part 4: Inoculation of cells onto the CAM

4.1.Preparation of cells

  1. Confluent cells are transferred from culture flask to FALCON tubes by the use of a sterile 25 ml plastic pipette using a pipette aid.
  2. To estimate cell number, 15 μl of the cell suspension is transferred to a Neubauer chamber and cells are counted manually under a microscope.
  3. Falcon tubes are centrifuged for 3 min at 1000 rpm at room temperature and the supernatant is discarded.
  4. For live cell tracking, cells are diluted with PBS to the desired concentration (here: 2x107 cells/ml) and stained with e.g. PKH26 (Sigma), a red fluorescent live cell membrane labelling kit, according to the manufacturers' protocol.
    Cells are re-suspended in cell culture medium (preferentially Dulbecco's modified eagle's medium; DMEM) to the desired concentration for injection (107 cell/ml) or inoculation (3x106 cell/ml). Different cell concentrations are applied for injections vs. inoculation according to concentrations already published in the literature15-17 and our experience.

4.2 Inoculation of cells onto the CAM

  1. Rings (~ 1mm thickness) are cut from a 1ml pipette tip or a peripheral venous catheter (PVL) tube by the use of a sharp scalpel and applied to the CAM of an E6-E14 chick embryo cultured ex ovo.
    Note: Try not to "saw" several times but to cut through the pipette tip or catheter tube with one cut using a new, very sharp scalpel to avoid sharp edges on the resulting rings. Check the rings under the microscope for sharp edges resulting from micro-cracks.
  2. Depending on the size of the rings 20 μl of 3x106 cell/ml cells are pipetted in total into one ring or as split volumes into multiple rings.
    Note: In some cases traumatisation of the CAM by gentle scraping is a pre-requisite, e.g. to facilitate inoculation of cells17 and capillarisation of grafts (see below). If, however, traumatisation of the CAM is not intended or contraindicative, e.g. for studies of the invasive potential of tumor cells, rings should not be used for inoculation, but cells should be applied directly as application of rings or rings themselves might induce micro lesion. If rings are used, these should be cut as thin as possible to minimize weight and avoid indentation of the CAM.

Part 5: Intravitreous injection of cells

  1. A Hamilton microliter syringe is rinsed several times with 70% EtOH and finally with sterile PBS.
  2. The micro syringe is filled with the prepared stained or unstained cell suspension (see Part 4.1).
    Note: The injection site has to be carefully chosen, not to injure blood vessels of the CAM or adjacent structures of the embryo (brain!) by over penetration with the needle. The injection should be done under a dissection binocular.
  3. Under microscope control, carefully, but quickly penetrate the CAM and eye layers with the syringe needle and continuously inject 10 to maximal 20 μl cell suspension (preferentially diluted in PBS) into the vitreous of the chick embryo cultured ex ovo.
    Note: If the CAM can not be penetrated with the needle, it might be removed at a site with few or no blood vessels by gently tearing it apart with two forceps.
  4. The needle should remain 1-2 seconds into the eye to avoid a loss of the injected cell suspension by leakage.

Part 6: Dissection of chicken limb buds

  1. Eggs are removed from the incubator after 3 to 4 days of incubation (E3/E4 = Hamburger Hamilton (HH) stage18-23)
  2. Eggs are cracked on the edge of a triangular magnetic stir bar and transferred into a Petri dish (details: see Part 2) and the embryo is dissected from the connected yolk vessels by cutting a circle using spring scissors.
  3. The embryo is transferred to a fresh Petri dish filled with cold, sterile PBS by use of a small drain spoon and washed by kind agitation.
  4. The embryo is transferred to a small Petri dish filled with sterile PBS and freed from surrounding membranes, carefully tearing them apart with fine forceps.
  5. Limb buds are detached by microsurgical forceps as close to the body as possible, grasped and transferred to the CAM of an 8-10-day-old host chicken cultured ex ovo (see grafting procedure).

Part 7: Preparation of mouse limb buds

  1. Time pregnant matings are set up and the morning of the day on which a vaginal plug is detected in females mating is designated gestation day 0.
  2. The pregnant female is sacrificed by cervical dislocation when the development of the embryos reached embryonic day (E) 10 to 13 and fixed on a wax board.
  3. The abdominal wall is moistened with 70% ETOH, cut along the midline and the skin flaps are fixed laterally by pins.
  4. Both horns of the uterus are removed from the abdomen, detached and transferred to a beaker with cold PBS.
  5. The embryos are separated, transferred to a Petri dish and uterus wall and embryonic membranes are removed carefully by the use of forceps.
  6. Limb buds are cut off by use of spring scissors or detached by fine forceps as close to the body as possible, grasped and transferred to the CAM of 8-10-day-old host chicken cultured ex ovo (see grafting procedure).

Part 8: Collection of tumor samples

  1. Tumor biopsies are collected in 2 ml Eppendorf tubes filled with tumor cell-specific culture medium (here: Leibovitz's medium) and kept at room temperature.
  2. Tumor biopsies are cut into 1-2 mm3 pieces by sterile scalpels.
    Note: If tumor samples were too small, they might not attach to the CAM, if they were too big, the CAM might be injured and the embryo might die.
  3. A piece from the core of the biopsy sample is grafted onto the CAM of 8-10-day-old host chicken cultured ex ovo (see grafting procedure).
    Note: Taking material from the surface of the biopsy increases the risk of contamination with muscle or connective tissue.

Part 9: Grafting procedure

  1. For grafting of limb buds or tumor specimens, the fully developed CAM of 8-10-day-old chick embryos cultured ex ovo is used.
  2. The grafts are ideally placed on the CAM near a Y bifurcation of a blood vessel.
  3. At the desired application site, the CAM is selectively traumatized by gentle scraping off (forceps) the upper peridermal part of the double epithelial layer, leaving the basal layer intact.
    Note: It is essential to avoid bleeding or visible rupture of capillaries.
  4. The graft is transferred to the CAM with minimal PBS attached. Depending on the graft, it might be placed once or twice on a site of the CAM, where no final grafting is intended to remove excessive PBS and then finally grafted at the prepared traumatized CAM site.
  5. The graft is grasped by fine forceps and layered onto the CAM. Depending on the sensitivity of the graft, light pressure might be applied (not suitable for limb buds) to manoeuvre the graft into a resulting indentation of the CAM (suitable for tumor samples).
    Note: As the chick immune system develops at embryonic day (E) 18, ex ovo xenografts cultures should not be prolonged beyond E17 as the host chick embryos frequently die.
    It is important to have available host CAMs, respectively chick embryos cultured ex ovo, timed to coincide with a source of donor tissue of your choice.

Part 10: Re-grafting

  1. The host chick embryo is killed by decapitation.
  2. The CAM with the attached graft is removed by a circular cut with pointed scissors and transferred to a Petri dish filled with PBS.
  3. Excessive CAM is cut from the graft by spring scissors except for the former attachment site.
  4. In case of bigger tumor samples, the graft is cut in halves or several smaller pieces and re-grafted with the cutting edge facing the new CAM of the second host.

Part 11: Representative Results

Figure 1
Figure 1. Shell-less chicken culture
Chicken embryos of different development stages cultured ex ovo in Petri dishes.

Figure 2
Figure 2. Ex ovo CAM angiogenesis assay
Fertilized chicken eggs were incubated horizontally at 37 °C and humidity of 60 - 62% and cracked into Petri dishes at embryonic day 4 (E4). Incubation was continued under the same conditions. At E10 sterile filter papers (5.5 mm in diameter) were layered on top of the CAM and soaked either with 5 μl PBS or 3 μg native angiotropin6. Capillaries showed obvious alignment towards the angiotropin soaked filter paper at E14.

Figure 3
Figure 3. Ex ovo grafting of limb buds
Limb buds from chick (E3/E4) and mouse (E13) were grafted onto the CAM of shell-less chicken cultures. Blood vessels from the CAM entered the limb buds after two days. The development of the limb buds continued in these ex ovo cultures reaching a two phalange stage in chick and displaying reduction of the interdigital webs in murine limb buds.

Figure 4
Figure 4. Ex ovo inoculation of tumor sample
A biopsy sample of bladder carcinoma was inoculated onto the CAM of a 10-day-old chick embryo cultured ex ovo. After two days in culture, the tumor specimen was connected to the CAM vasculature and after 7 days, multiple blood vessels entering the graft were observed.

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Discussion

Innovative or just another chick culture protocol?

With former shell-less culture protocols1-4 the total survival rates of the chick embryos were low, e.g. ca. 30%1. The refined ex ovo culture protocol described in this video article, by contrast, allows for survival rates over 50%. Compared to classical in ovo cultures ex ovo culture of chick embryos significantly facilitates the accessibility of the CAM and chick embryo and enables their experimental manipulation and continuous monitoring. This culture method can be used for a wide variety of application ranging from enhanced angiogenesis assays5,6, to facilitated injections in the vitreous of the chick embryo eye7-9, intravasation assays10-12, improved grafting and growth of limb buds13 and innovative maintenance of tumor samples14. Thus, ex ovo culture contributes a useful tool in developmental, angionesis and tumor research.

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Acknowledgements

The authors would like to thank J. Kueper and J. Wittschier for excellent technical assistance and Prof. Ruebben for generously supplying tumor material.

Materials

Name Type Company Catalog Number Comments
Fertilized Eggs Animal Sorries-Trockels Vermehrungszucht GmbH
Mice Animal Charles River Laboratories
Incubator Type 3000 with rotating egg tray Tools Siemens AG 9503 Maintain at 37°C with relative humidity set above 60%
Egg incubator BSS 160 Tools Grumbach, Germany 8101 Maintain at 37-387deg;C with relative humidity set above 60%
PBS Reagent Sigma-Aldrich PBS should be cold (> 4°C) and sterile
Dulbecco’s modified eagle’s medium Reagent Sigma-Aldrich D 6429 DMEM culture medium
Leibovitz’s L-15 Medium Reagent Invitrogen 31415-029 here: collection medium for tumor samples
Tumor cell -specific medium Reagent Sigma-Aldrich each research group should use the medium they culture their tumors cells in or common culture media, e.g. Leibovitz’s Medium or Dulbecco’s modified eagle’s medium
supplemented with 15% fetal bovine serum (FBS), 4mM L-glutamine and 50 μM insulin
70% EtOH Reagent Sigma-Aldrich
Magnetic stir bar, triangled 80 mm Tool VWR international 442-0391 A triangled magnetic stir bar serves well to crack the eggs shell.
Forceps DUMONT #5 Tool Fine Science Tools 11252-30 bevelled very fine shanks (0.05 mm x 0.02 mm tip)
Forceps DUMONT #7 Tool Fine Science Tools 11271-30 curved shanks (0.07 mm x 0.10 mm tip)
Spring scissors, straight, 8cm Tool Fine Science Tools 15000-00 fine, small straight blades
Fine Iris scissors, straight Tool Fine Science Tools 14094-11 Use to cut our the CAM
Standard scissors, straight, sharp/blunt Tool Fine Science Tools 14007-14 Use for decapitation or cervical dislocation
microliter syringe 1702 TLLX, 25 μl Tool Hamilton Co 80222 Use for injection into the vitreous
Hamilton 33-G needle (15 mm) Tool Fine Science Tools 18073-15 Use for injection into the vitreous
Sterile scalpels Tool Use for dissecting tumor samples
Small drain spoon Tool Geuder 15758 Use to transfer of small chick embryos
Wax board with fixing pins Tool Home made Use to fix of animals for dissection
Petri dishes 60 x 15 mm Tool Greiner Bio-One 628102
Petri dishes 92 x 16 mm Tool Sarstedt Ltd 82.1472
Sterile Petri dish 100 x 20 mm Tool Greiner Bio-One 664160 extra deep, with spacers for ventilation
Beaker Tool 300-600 ml
FALCON tubes Tool Falcon BD 15 ml and 50 ml
Eppendorf tubes Tool Eppendorf 1.5 ml and 2 ml
1ml pipette tips Tool Use to cut plastic rings for application of substances / cells
Peripheral venous catheter (PVL) Tool Viggo® Use to cut silicon rings from the tube for application of substances / cells
Pipettes and tips Tool Eppendorf
Autoclaved folded Filters 595 1/2, 110 mm diameter Tool Schleicher Schuell 311643 Carrier, which caused least irritation of the CAM; used in the paper
PTFE-Pledget, non resorbing, 6,3 x 152.4 x 1.6 mm Tool santec-medical REF 277, LOT 832/511-1 Carrier; caused false positive results
Hxdroxyethylcellulose Tylose H 100000 Reagent Carrier mixed with Kollidon 17 PF; caused false positive results
Kollidon 17 PF Reagent BASF S30200 mixed with Hydroxyethylcellulose; caused false positive results
Collagen Biomatrix TissuDura Tool Baxter Internationl Inc. REF B2246000999999 Carrier; caused false positive results
Round glass cover slips, 11 mm Tool Assistent Germany 1001/0011 Carrier; causes false positive results
Bovine Collagen Sponge Tool Wyeth Animal Health Carrier; caused false positive results
Resodont Absorbable Collagen Membrane Tool Resorba Woundcare Germany LOT 280303 Carrier; caused false positive results
Non-Woven Swabs Tool Fink Walter GmbH REF 328132 Carrier; caused false positive results

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References

  1. Auerbach, R., Kubai, L., Knighton, D., Folkman, J. A simple procedure for long-term cultivation of chicken embryos. Dev. Biol. 41, 391-394 (1974).
  2. Tufan, A. C., Akdogan, I., Adiguzel, E. Shell-less culture of the chick embryo as a model system in the study of development neurobiology. Neuroanatomy. 3, 8-11 (2004).
  3. Deryugina, E. I., Quigley, J. P. Chick embryo chorioallantoic membrane models to quantify angiogenesis induced by inflammatory and tumor cells or purified effector molecules. Methods Enzymology. 444, 21-44 (2008).
  4. Ribatti, D. Chick embryo chorioallantoic membrane as a useful tool to study angiogenesis. Int. Rev. Cell Mol. Biol. 270, 181-224 (2008).
  5. Höckel, M., Sasse, J., Wissler, J. H. Purified monocyte-derived angiogenic substance (angiotropin) stimulates migration, phenotypic changes, and "tube formation" but not proliferation of capillary endothelial cells in vitro. J. Cell Physiol. 133, 1-13 (1987).
  6. Wissler, J. H. Engineering of blood vessel patterns by Angio Morphogens [Angiotropins]. Materialwiss. Werkstofftech. 32, 984-1008 (2001).
  7. Kistler, H. B. J. r., LaVail, J. H. Penetration of horseradish peroxidase into the optic nerve after vitreal or vascular injections in the developing chick. Invest Ophthalmol. Vis. Sci. 20, 705-716 (1981).
  8. Halfter, W. Change in embryonic eye size and retinal cell proliferation following intravitreal injection of glycosaminoglycans. Invest. Ophthalmol. Vis. Sci. 49, 3289-3298 (2008).
  9. Oppitz, M., Busch, C., Shriek, G., Metzger, M., Just, L., Drews, U. Non-malignant migration of B16 mouse melanoma cells in the neural crest and invasive growth in the eye cup of the chick embryo. Melanoma Res. 17, 17-30 (2007).
  10. Uchibayashi, T., Egawa, M., Nakajima, K., Hisazumi, H., Tanaka, M., Endo, Y., Sasaki, T. Responses of tumour cell lines implanted onto the chorioallantoic membrane of chick embryo to anticancer agents in combination with hyperthermia. Urol. Res. 20, 237-239 (1992).
  11. Demir, R., Naschberger, L., Demir, I., Melling, N., Dimmler, A., Papadopoulus, T., Sturzl, M., Klein, P., Hohenberger, W. Hypoxia generates a more invasive phenotype of tumour cells: an in vivo experimental setup based on the chorioallantoic membrane. Pathol. Oncol. Res. (2008).
  12. Kunzi-Rapp, K., Genze, F., Kufer, R., Reich, E., Hautmann, R. E., Gschwend, J. E. Chorioallantoic membrane assay: vascularized 3-dimensional cell culture system for human prostate cancer cells as an animal substitute model. J. Urol. 166, 1502-1507 (2001).
  13. Hall, B. K. Grafting of organs and tissues to the chorioallantoic membrane of the embryonic chick. TCA Manual. 4, (3), 881-883 (1978).
  14. Kunzi-Rapp, K., Kaskel, P., Steiner, R., Peter, R. U., Krahn, G. Increased blood levels of human S100 in melanoma chick embryo xenografts' circulation. Pigment Cell Res. 14, 9-13 (2001).
  15. McFall, R. C., Sery, T. W., Makadon, M. Characterization of a new continuous cell line derived from a human retinoblastoma. Cancer Research. 37, 1003-1010 (1977).
  16. Deryugina, E. I., Zijlstra, A., Partridge, J. J., Kupriyanova, T. A., Madsen, M. A., Papagiannakopoulos, T., Quigley, J. P. Unexpected effect of matrix metalloproteinase down-regulation on vascular intravasation and metastasis of human fibrosarcoma cells selected in vivo for high rates of dissemination. Cancer Research. 65, 10959-10969 (2005).
  17. Kim, J., Kovalski, K., Ossowski, L. requirement for specific proteases in cancer cell intravasation as revealed by a novel semiquantitative PCR-based assay. Cell. 94, 353-362 (1998).

Comments

8 Comments

  1. Though i subscribe your journal but still i am unable access the required paper. How could i get that paper please tell me.

    Reply
    Posted by: Anonymous
    April 16, 2010 - 8:38 AM
  2. Hello,

    You need to be logged in to access the paper. If you are logged in and are still unable to access this please contact us directly and we will resolve this, support@jove.com. Thanks.

    -Chris

    Reply
    Posted by: Chris M.
    April 16, 2010 - 11:21 AM
  3. I subscribed for a free trial, and although I can see the paper, I am unable to watch the video.

    Reply
    Posted by: Carolina L.
    June 9, 2010 - 10:42 AM
  4. We are attempting to follow the method described, but have found the eggs over a short amount of time seems to "ooze" all over the place and lose shape. This is even when broken gently and looking perfect when placed into the dish. I have seen other notes of using glass dishes, or using "hammocks" made of cling wrap that would physically hold the yok together in the center. Can you offer any suggestions as to why we might be encountering this problem. Thanks for any advice.

    Reply
    Posted by: Anonymous
    April 4, 2011 - 3:22 PM
  5. We have found both the "oozing" described above to be a problem for some of our eggs, but also a loss of viability at around day 5-6 even for many of those that look initially perfect. We care curious about the exposure to light that some investigators caution against, the type of plate (glass vs. plastic - tissue culture treated vs. untreated), and we are also trying low adherence plates. We will appreciate any advice.

    Reply
    Posted by: Anonymous
    May 4, 2011 - 1:01 PM
  6. I tried to treat Whatmann filters with 10 or 100 ng VEGF (vs. PBS control) for three subsequent days (the initial placement was on day 8) and to evaluate angiogenesis on day11 and 1². However, no effect was observed. What can you recomment me, please? (different outline of the experiment, dosage, quantification method?)
    As for cell application using rings, I added 1.5 x 10^5 DU-145 cells in 40 ul of MEM on day 8 (compared to MEM control, or disc without substances). Evaluation of angiogenesis on days 11 and 1² showed no difference between the treatments. Which cell line do you recommend, please?

    Reply
    Posted by: Anonymous
    May 26, 2011 - 8:49 AM
  7. What did you do to discard your embryo at the end of your experiement?

    Reply
    Posted by: Anonymous
    June 9, 2011 - 1:10 PM
  8. If I am using a cell culture incubator what percentage of O2 do I have to supply in an ex ovo culture?

    Thank you

    Reply
    Posted by: Daniel P.
    March 1, 2017 - 5:23 PM

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