Lithium Chloride and Trypan Blue Induce Abnormal Morphogenesis by Suppressing Cell Population Growth: (LiCl/trypan blue/chick teratogenesis/cell population growth inhibition).

Full primitive streak stage chick embryos were cultured in vitro for 20 hrs and monitored every 4 hr for morphology, cell number and blastoderm area. In normal embryos, the cell population growth is exponential and correlates directly with Increasing morphological rank. The chick blastoderm area expands in two waves, one immediately after gastrulation and another after 16 hr in culture, while cell population growth is predominant between 4-16 hr. Trypan blue and LiCI inhibit cell population growth, epiboly and shaping of organ primordia. Both teratogens induce a similar spectrum of abnormalities although the severity of abnormal development is greater with LiCl for the given dose. In most abnormal embryos the cell population size and blastoderm area are inhibited most, which is detectable already after 12 hr of culture. We have established that the cell population growth, morphogenesis and area expansion constitute a parametric hierarchy with the cell population growth as the most independent parameter in regulating normal morphogenesis.

Cell Population Growth and Area Expansion in Early Chick Embryos During Normal and Abnormal Morphogenesis in vitro: (trypan blue, chick embryo/teratogenesis/cell population growth/blastoderm expansion).

The exponential growth and cell population during the early embryogenesis of chick, cultured in vitro correlates with a linear increase in the blastoderm area. To understand the relationship between these parameters and normal morphogenesis, we have used a known teratogen, trypan blue, as a probe. A method is developed in which each new embryonic structure is assigned a rank value of 1 and the total number of ranks allows quantification of development and establishment of a numerical relationship between the size of the cell population, blastoderm area and the morphological development. The teratogen inhibits cell population growth, morphogenetic movements and shaping of organ primordia, but not the epiboly and differentiation of cells which have already invaginated and positioned during primitive streak formation. In contrast, the cell population growth, but not the blastoderm area-expansion, is correlated with the extent of abnormal development. A graphic analysis of the rank order, log cell number and blastoderm area reveals that these three parameters coordinately regulate morphogenesis. It is suggested that head fold formation is the key event regulating the progress of early morphogenesis.

Effects of cytochalasin H on developing frog embryos: reversibility of action.

Cytochalasin H (CH) brought about cellular disaggregation resulting into arrest of development in the embryos of the frog, Microhyla ornata. The effects were dependent on the dose of CH, duration of the treatment as well as on developmental stage of the embryo at the beginning of the treatment. The embryos were protected to some extent if the vitelline membranes were left intact. The reversibility of CH-action, after transfer of treated embryos to CH-free medium, was dependent on the extent of cellular disaggregation brought about by CH and on the presence or absence of an intact vitelline membrane.

Study of catheptic and acid phosphatase activities during development and metamorphosis ofDrosophila melanogaster.

Developmental stages ofDrosophila melanogaster cultured at 22 ± 1° C were collected and tested for catheptic activity and acid phosphatase activity.It was found that catheptic activity was absent in the egg as well as in the first and second larval instars. The activity first appears in the third instar larva and reaches its peak 24 to 48 hr after puparium formation. It then decreases, at first gradually and at pupal stage 9 (120 to 144 hr after puparium formation) abruptly, reaching zero level just before the emergence of the imago.The pattern of acid phosphatase activity in different developmental stages was found to be broadly similar to that of catheptic activity in the larval and pupal stages. However, the acid phosphatase activity was found to be exceptionally high in the egg in contrast to the catheptic activity.