Wilhelm Roux's archives of developmental biology最新文献

In vitro experiments were carried out to determine the effects of prolactin, and prolactin in combination with other hormones on the regeneration of adult newt tail blastemata. A total of 271 blastemata were explanted 13 days postamputation and were organ cultured for 96 h at 20 (±1)°C. Treatment with prolactin alone resulted in an increase in the blastema cell density of the tail regenerates. Cell accumulation and cell alignment were observed ventral to the reconstituted spinal cord. Prolactin and thyroxine, in combination, improved development of tail regenerates as compared with treatment with prolactin or thyroxine singly, supporting the results of earlier in vivo studies. Optimal development was obtained only when prolactin, insulin, thyroxine and hydrocortisone were added to the culture medium. Regeneration of tail explants maintained in medium augmented with the four hormones closely resembles that of in vivo tail blastemata 17 days post-amputation.

The fusion of the eye-antennal discs during culturein vitro has been investigated, and the complex morphogenetic movements which occur during the formation of the head capsule of the insect are described. The initial contact between the eye anlagen is by means of cell processes spanning the gap between the two discs. Subsequently the two epithelia become firmly apposed, and then the integrity of the epithelium in the region of fusion breaks down, cells appearing to move to new positions in order to form an epithelium which unites the two discs. The epithelium eventually secretes a pattern of cuticular structures which is continuous between the derivatives of the two discs. Bristles on either side of the line of fusion are perfectly aligned, and structures such as the median ocellus, which are formed jointly by the cells of the two discs, differentiate normally. This is also found when left and right eye-antennal discs of different genotypes are placed side-by-side, indicating that processes of pattern regulation can occur in culture.

Supernumerary limbs were produced by deviating the sciatic nerve to the surface of the axolotl hindlimb either alone or in combination with small skin grafts from specific limb positions. With no skin grafts a very low frequency of good supernumeraries were produced. However, when associated with skin grafts, this frequency was significantly increased. The pattern of skeletal elements and muscles were analysed in the supernumeraries which formed at each location. In both the anterior-posterior and dorsal-ventral axes specific anatomical features were found which correlated with their position of origin on the host limb. Characteristic features were also observed with respect to the proximal-distal axis of the outgrowths. These phenomena are discussed in relation to our current understanding of the rules of pattern regulation in the regenerating limb.

The changing pattern in free amino acids following the embryonic development in the non-diapause and diapause eggs of thepnd mutant of theBombyx silkworm was studied. In the diapause eggs, heterozygous for thepnd gene, the levels of most of the amino acids increased concomitantly with the substantial decrease in oxygen consumption. Among the amino acids, alanine was the only amino acid that showed a large accumulation. The accumulation could be induced experimentally in the non-diapause eggs, homozygous for thepnd gene, by reducing the oxygen supply. In contrast, it was prevented in the diapause eggs by increasing the oxygen supply. From these results, it is suggested that the alanine accumulation is the consequence of anaerobic metabolism in the eggs during diapause. The possible significance of the alanine accumulation is discussed in relation to the anaerobic carbohydrate metabolism associated with the embryonic diapause in thepnd mutant.

A method utilizing microinjection of glycosaminoglycan-degrading enzymes in the chicken blastoderm prior to embryo culture and immunostaining for fibronectin have been applied to demonstrate an interaction between glycosaminoglycans and fibronectin in the basement membrane of the epiblast. Fixation of tissue in a mixture of formaldehyde and cetylpyridinium chloride allows detection of fibronectin only in those zones of the embryo that are not colonized by mesoblast cells. The epithelial-mesenchymal interface thus remains unstained. After degradation of glycosaminoglycans in the living organism, it is shown that this particular site, in fact, also contains fibronectin that is masked in vivo by, at least, hyaluronate. This interaction between both compounds is, during gastrulation, constantly correlated with mesoblast migration. Since previous studies have shown that the degradation of hyaluronate determines the behaviour of mesoblast cells, it is proposed that remodelling of the interaction between these compounds is necessary for mesoblast migration to occur.

Hydractinia echinata is a marine, colony-forming coelenterate. Fertilized eggs develop into freely swimming planula larvae, which undergo metamorphosis to a sessile (primary) polyp. Metamorphosis can be triggered by means of certain marine bacteria and by Cs⁺. Half a day after this treatment a larva will have developed into a polyp. The induction of metamorphosis can be prevented by addition of inhibitor I, a substance partially purified from tissue ofHydra. The larvae ofH. echinata also appear to contain this substance. Inhibitor I appliedafter the onset of metamorphosis blocks its continuation as long as it remains in the culture medium. Cs⁺ applied within the same period of time also blocks the continuation of metamorphosis. However, these two agents have opposite effects on the body pattern of the resultant polyps. The experiments indicate that application of Cs⁺ triggers the generation of the pre-pattern. Inhibitor I appears to be a factor of this prepattern. A model is proposed which describes the basic features of head and foot/stolon formation not only forHydractinia but also for other related hydroids.