Development of the ectopia cordis induced by hydrocortisone administration.

Our previous study on the development of thorax in chick embryos revealed that mechanical disturbance of the so-called membrana reuniens causes the development of the ectopia cordis (EC). To assess whether membrana reuniens disturbance was really essential for EC development, we employed hydrocortisone, a teratogen known to produce a high incidence of EC. The incidence of EC after the hydrocortisone intraamniotic application on the 4th embryonic day reached 84,8%. It was found that although in the whole course of EC development the membrana reuniens appeared very thin, it nevertheless remained continuous. The morphology of the membrana reuniens in embryos with fully developed EC, studied in classical serial histological sections, was similar to that of the amniotic membrane. Flow cytometry analysis of the cell cycle revealed that EC induced by hydrocortisone administration was associated with a significantly lowered proliferation activity of the prospective body-wall mesenchyme involved in the closure of the anterior wall of thorax. The probable mechanism of EC development is suggested.

Development of spatial relations of shoulder and brachium in embryonal chick wing.

The linear marking method was employed to study morphogenetic movements of tissues involved in the development of the definitive position and shaping of the shoulder and arm. Chick embryos in the range of embryonal day 3.5 to 4.5 were used with the following results: -Asymmetrical growth of the early wing bud and the oblique position of humerus anlage in the early wing bud as proposed by Saunders (1948) and Seichert (1965) were confirmed. -It was found that the cranial ascend of the shoulder (Seichert and Knospe 1992) is accompanied by the slight ventromedial rotation of the complex consisting of the scapula and coracoid. -Torsion along the longitudinal axis of the stylopodium was observed: the proximal part of the stylopodium (both the humerus anlage and related soft tissues) moves in the sense of supination, the distal part moves in the sense of pronation.

The rearrangement of the cranial part of embryonal body in chick studied by linear marking. II. Relations of the neck, thorax and shoulder.

The linear marking method was employed for studying morphogenetic movements of tissues involved in formation of the cranial part of the chick embryonic body. A total of 120 chick embryos marked on days 3-5 were used in this study with the following results: The cranial shift of axial structures and somites with respect to the other components of the cranial part of the embryonic body, described in our earlier papers, has been proven. This shift is considered crucial from the point of understanding and proper interpretation of the following formative processes: The prospective mesenchyme of the wall of the thorax shifts continuously in the cranial direction. The rate of the shift of the mesenchyme in the dorsal part of the developing body wall appears considerably lower than that of the somites. The cranial shift of the mesenchyme of the ventral part of the body wall is directed ventromedially and proceeds more rapidly than in the dorsal part of the body wall. The ventromedial deviation of the cranial shift is gradually increased in the craniocaudal sequence. In this way, the mesenchyme of the lateral body wall replaces step by step the membrana reunions to cover the heart, rapidly growing lungs and the liver. The presumptive shoulder shifts cranially at the rate similar to that of the somites. In this way, the shoulder slides over the body wall mesenchyme formerly located in the more cranial position. The shoulder undergoes rotation by the mechanism which is discussed.

The topogenesis of the thyroid in chick embryos.

Using the technique of linar marking on the embryonic thyroid of chicken, it was proven that the thyroid anlage after its evagination from the primitive pharynx, does not undergo any caudal migration. Its topogenesis is influenced by two main mechanisms. First, the relative craniocaudal displacement follows from the cranially oriented growth of the neck and second, the enlarging oesophagus presses the trachea ventrally against the thyroid anlage promoting its division and separation of both lobes.

Significance of the differential growth, relative tissue shifts and the vascular bed in limb development.

1. A method for planimetric measurement of areas of standardized dorsoventral projections of embryonal limbs was elaborated. The method permits a quantitative study of the growth of embryonic limbs at early stages of development, since the stage of flat limb bud until the stage at which the external shape of the limb (bending in joint regions and increase in volume) interferes with the simplification of its three-dimensional characteristics to two-dimensional ones of its dorsoventral projection. (Until stage 31-32HH for the chick embryo, see fig. 1 and 2). 2. A method of linear marking was elaborated (fig. 3). The marker proper are India-ink particles suspended in gelatin. Such stained gelatin is spread over a glass carrier (a glass fibre 10-20 microns thick) in the form of a thin film. After drying the fibre is cut in rods of a length desired for the appropriate linear mark. The marks can be introduced into the tissue by a single stab. After the gelatin film had swollen owing to the presence of tissue fluids, it is detached from the carrier surface and the carrier can be removed from the tissue. After the gelatin had been resorbed, a linear mark remains in the tissue. Deformations of the mark line and the scattering of India-ink particles which actually form the mark facilitates the assessment of the growth pattern of the respective marked tissue (see fig. 4-6). 3. During our studies of the differential growth of the wing bud with the method of linear marking the newly coined term "relative tissue shift" had to be specified. That term has been used for designating changes of the mutual position of tissue areas which could not be defined exactly as to their topography within a region or organ (such as the wing bud), showing fluent transitions between one another. If areas with different growth activities occur in the region studied, such areas undergo an uneven increase (differential growth). Thus another factor is added to those operating in the growth process, namely the direction of expansion of the different growing areas of the region studied to one another. The resultant of the mutual ratios of the voluminal growth of the neighbouring tissue areas and the directions of their expansion are the relative tissue shifts in the sense used in our studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential growth and tissue shifts in the developing neck of the chick embryo. An experimental study.

The differential growth of the neck was studied by means of linear marks in the chick embryo. The marks were inserted into 3 different zones: Zone I, between the level of 1st and 2nd branchial cleft, zone II, between the level of the 2nd and 3rd branchial cleft, and zone III, between the level of the 3rd branchial cleft and the Cuvier duct. The deformation and dispersion of marks after further incubation of labelled embryos indicate: 1. A caudocranially oriented growth of axial and paraaxial structures causing the displacement of branchial to axial and paraxial structures, 2. an extent growth in the region of the 3rd branchial arch in contrast to other branchial arches with 2 exceptions: the extent craniocaudal growth of the operculum (2nd branchial arch) and the extent caudocranially oriented growth of the hypobranchial region. On the base of our findings the differences in the topography of some neck organs of birds and mammals could be explained.