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Biomedical subjects

L Vakaet

Publications and source records attributed to L Vakaet.

72 records · Page 4Linked to original sources
PubMed1977

Invasion of malignant cells into cultured embryonic substrates.

To study malignant invasion, we associated tissue and cell culture fragments, with adhesive and non-adhesive living substrates in vitro (11). Non malignant mesonephros, quail heart and BHK-cells, as well as malignant HeLa-, Hepatoma-, Harding-Passey melanoma-, Py-, TLX5 lymphoma- and Schmidt-Ruppin sarcoma cells, were transplanted into cultured organ fragments of chick embryos and chick blastoderms. Malignant invasion was evaluated on the basis of the following histological criteria: 1. changes in organization of the graft. 2. infiltration of cells from the graft into the substrate, 3. degenerative alterations of the substrate. It was shown that adhesion of the graft to the substrate is a prerequisite for malignant invasion. Invasion into non-adhesive substrates, such as the apical side of epithelia, was never observed. Contrary, all malignant cells did invade into adhesive substrates. Interposition of a vitelline membrane always inhibited the expression of invasiveness. The morphological pattern of invasion depended mainly on the architecture of the substrate and differential resistance of its various components explained well all histological pictures. From the latter observation and from the localization of degenerative changes in the substrate we inferred that malignant cells exert their deleterious effect most probably upon immediate contact with their host.

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PubMed1975

Characterization of spontaneous, chemicak, and viral transformants of a C3H/3T3-type mouse cell line by transplantation into young chick blastoderms.

Cells from a C3H/3T3-type cell line were transplanted into defects of the lower layer of stage-4 chick blastoderms before and after "spontaneous," chemical, and viral transformation. To check the validity of inhibition of lower-layer defect closure as a criterion of malignancy, we compared the behavior of the lower layer toward these cells with their in vitro growth pattern, their capacity to invade embryonic chick skin explants that were organotypicaly cultured, and their tumorigenicity in syngeneic mice. No false-positive results were observed with either test. The study of the in vitro growth pattern gave false-negative results during the early phase of spontaneous transformation, whereas these cells, exhibiting an untransformed growth pattern, were shown to be malignant by the other tests. We concluded that the inhibition of lower-layer defect closure is a reliable, sensitive and rapid test for the detection of malignancy in tissue-cultured cells from any source.

Animals↗
PubMed1975

Adhesion of malignant and nonmalignant cells to cultured embryonic substrates.

To study adhesion, which is probably the initial step in malignant invasion, we associated tissue culture fragments with living substrates in vitro. Malignant HeLa, hepatoma, and PY cells, as well as nonmalignant BHK cells, were transplanted into cultured chick blastoderms and organ fragments from chick embryos. Adhesion was evaluated by time-lapse cinematography, by flushing with Tyrode's solution, and by histological examination after fixation. It was shown that the adhesion of these tissue culture fragments depends on the nature of the substrate. Substrates of connective tissue, mesenchyme, and the basal side of epithelia proved to be adhesive. In contrast, the apical side of intact epithelia was nonadhesive. Perforated epithelia allowed adhesion at the site of the perforation. In the presence of dilysine, HeLa cells adhere to the apical side of epithelia and to the dorsal side of the upper layer of the blastoderm. We concluded that the apical side of intact epithelia constitutes an inappropriate substrate for adhesion of a large variety of cells, in vitro as well as in vivo. Alteration of this characteristic in the presence of dilysine indicates that long-range electrostatic repulsion might be responsible for the nonadhesive character of the epithelia.

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PubMedDate not supplied

Early expression of muscle-specific molecules in avian embryos.

With an antibody against whole embryonic chick heart, avian embryos of different stages were stained from beginning of cardiogenesis on. The earliest positive staining was encountered in a stage where heart tissue was already morphologically recognizable. This was also the case for myotomes and extrinsic eye muscles. Positive staining with anti-desmin of the same stages was possible slightly later. At the onset anti-desmin showed a staining pattern different from that of anti-heart staining.

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