Wilhelm Roux Archiv Fur Entwicklungsmechanik Der Organismen最新文献

Developmental capacities of imaginal disc tissue sublines were correlated with their growth rate, morphology, histology and fine structure. Tissue sublines were derived from half an eye-antennal disc ofDrosophila melanogaster and were serially subculturedin vivo in the abdomens of adult female flies for over 150 transfer generations (8 years and more than 1000 cell divisions). During this period the capacities for differentiation of the tissue sublines were repeatedly tested by implantations into larvae for metamorphosis. At the outset the tissues behaved autotypically and metamorphosed into eye and antennal structures. They then transformed in one of three ways: they underwent transdetermination to become allotypic and metamorphosed into structures belonging to another disc; they became anormotypic and metamorphosed into abnormal cuticular patterns; they became atelotypic and failed to make any cuticle when caused to metamorphose. All allotypic sublines gradually became anormotypic and finally atelotypic. The results show that atelotypic tissue sublines arise in two ways: directly from autotypic tissues or gradually from auto-, allo-, or anormotypic tissues.One gradually transformed atelotypic tissue line which had failed to make cuticle for four years and 59 transfer generations, although repeatedly tested, was enabled to regain the capacity to secrete cuticle by subculturing at low temperatures in abdomens of adultD. virilis where the implanted tissues grew slowly.Allo-, anormo-, and atelotypic changes were associated with a marked increase in rate of proliferation and with characteristic changes in tissue and cell structure. Auto- and allotypic tissues are composed mainly of columnar or cuboidal imaginal disc epithelial cells arranged in monolayers, with a regimented array of microvilli on their apical surface, a smooth basement membrane on their basal surface, and extensive intercellular junctional complexes. They form sac-like structures when subcultured in adult abdomens. Anormotypic tissue is a mosaic of regions with cells in monolayers and in compact masses. The cells in both arrangements resemble imaginal disc cells in their staining properties. However, the cells in these monolayers do not have well developed microvillar surfaces and their basement membranes are curled and detached from the cell surface. The cells in compact masses appear to be modified imaginal disc epithelial cells which possess neither a microvillar surface nor a basement membrane and have far fewer intercellular junctional complexes than do imaginal disc epithelial cells.Atelotypic tissue sublines are composed primarily of cells in a compact mass and form a solid ball when cultured in adult abdomens. These masses contain numerous lacunae and are comprised of three cell types with characteristic morphology and staining properties, designated as intensely staining cells, faintly staining cells, and elongated cells. The intensely staining cells resemble the modi

The distribution of XX- and XO-areas within the cuticle and in the internal organs was examined in 355 adult gynandromorphs of the genotypeR(1)2,In(1)w ^vC /y w sn ³ lz ^50e mal, whereby XO-areas could be recognized by the phenotypes of the recessive alleles on the rod-X-chromosome.The percentage of gynandromorphs in which selected pairs of structures show different genotypes is taken as a measurement (in sturt-units) for the distance between the presumptive areas of these structures in early developmental stages. The calculated distances between cuticular structures (Table 2) agree well with those reported by Hotta and Benzer (1972). The structures of internal organs were therefore localized in the fate map of Hotta and Benzer. The resulting morphogenetic map (Fig. 1) is discussed in comparison with Poulson's embryonic fate map.

1. Anterior halves of 6-hour-old embryos, in which the primordia of the salivary glands are not yet visibly segregated, have been transplanted into the abdomen of adult females. 2. Normal larval salivary glands differentiate in the adult hemolymph and attain the maximal degree of nuclear size due to polytenisation. 3. In the adult hemolymph, a culture period of 14 days is needed for full development whereas the same end-size is reachedin situ after 4 days. 4. The retardation in growth rate is accompanied by a reduction in cell numbers. 5. It is concluded that the adult hemolymph can provide all factors needed for the entire development of larval salivary glands. 6. The difference between the adult medium and the normal larval milieu which promotes a more rapid development might be only of a quantitative nature. Tentatively, we consider differences in hormonal concentrations.

Deuterencephalic and spinocaudal inducing activity is extractable from the yolk platelet coats and the microsomal fraction of cleavage, gastrula and neurula stages ofXenopus laevis.Extracts of both cell fractions from the gastrula and neurula cause a significantly stronger deuterencephalic and spinocaudal reaction than those from cleavage stages, when tested anTriturus alpestus ectoderm.

Serotonin distribution in early Ophryotrocha embryos was investigated with fluorescence microscopy based on formaldehyde gas treatment of the embryos, and with light- and electron-microscopic autoradiography after the embryos had been treated with³H-5-hydroxytryptophan.Sections of early cleavage embryos showed serotonin-specific fluorescence all over the blastomeres, but it was mainly concentrated on yolk granules, and to a lesser degree on lipid drops and vacuoles. In 2-8 cell embryos, marked regional concentration of serotonin fluorescence was noticeable along the completed cleavage furrows.The autoradiographs confirmed the picture of the yolk granules as the principal site of serotonin formation and serotonin accumulation; considerable amounts were also associated with their decomposition products, i.e. lipid drops, vacuoles, and vesicles, whereas major cell organelles, e.g. mitochondria, were almost totally lacking. Of cytoplasmic structures in the blastomeres without apparent yolk granule origin, only microfilaments, particularly those amassed along the cleavage furrow, showed consistent and significant association with formed serotonin. This suggests a connexion between serotonin and microfilaments and might imply that in early embryo cells the fundamental contractile machinery is controlled by serotonin gradually released from the yolk granules.Within the blastomere nuclei, moderate amounts of serotonin were demonstrated with both fluorescence microscopy and autoradiography.The monoamine oxidase (MAO) inhibitor catron^® (phenylisopropylhydrazine), used to intensify the autoradiographic picture of serotonin in the Ophryotrocha embryos, markedly increased intragranular serotonin accumulation, but also retarded yolk granule disintegration and delayed the cell cleavage process. In embryos barely able to cleave after treatment with catron^®, ultrastructural analysis demonstrated that membrane formation at cell cleavage depends on influx of material from the nearby disintegrating yolk granules.

Anterior fragments of mature haltere discs are shown to regenerate missing anlagen when allowed additional growth in adult hosts. It appears that a small part of the scabellum anlage, and perhaps even the metathoracic anlage alone, is capable of regenerating a complete haltere. Posterior fragments are capable of duplicating the anlagen present in them, often with perfect mirror-image symmetry. Symmetrical structure is already observed in the cultured disc fragments prior to differentiation in the final host. Beside polarized duplication, local multiplication of units or size increase of structures was observed.The present results are interpreted in terms of a monotonic gradient of positional value running through the dise in an anterior-posterior direction. Fragments containing higher parts of the gradient would be able to regenerate lower parts in the blastema during growth, whereas in the case of proliferating fragments containing lower gradient parts a zero boundary would be established at the tip of the blastema, leading to polarity reversal in the middle of the total tissue mass.

The fine structure of the neoblasts in the naidOphidonais serpentina has been examined. The neoblasts of control worms have a relatively large nucleus, containing a large nucleolus, a sparse amount of rough endoplasmic reticulum, and an abundance of free ribosomes and mitochondria. Although Golgi membranes have been demonstrated, there is no evidence that the neoblasts are secretory in nature. Neoblasts form loose cell-to-cell contacts with one another and with peritoneal cells. In worms 12 hours after posterior transection, the neoblasts found at the end of the severed ventral nerve cord have rounded up and are no longer spindle-shaped. Counts of neoblasts immediately after posterior transection indicate that they are equally distributed in the last five segments. A statistical analysis of their distribution during posterior regeneration reveals a significant increase in neoblasts in the last three segments and a migration of neoblasts toward the wound. The role of neoblasts in oligochaete posterior regeneration is discussed.

The timing hypothesis of Curtis proposes that cells which go through a sequence of types of behavior at different rates sort out from one another in aggregates. In order to further test this hypothesis we have given cells from one chick embryo tissue a head start in aggregating before adding cells from a second tissue. By such experimental manipulation the normal position of cells in an aggregate should be reversed, according to predictions from the timing hypothesis. When heart ventricle cells were allowed to aggregate 6,12, 20, or 22 hours before addition of neural retina cells, the aggregates all showed internal heart cells surrounded by neural retina cells. The same final positions of heart and neural retina were found in aggregates in which neural retina cells started aggregating 4, 6, or 22 hours before addition of heart cells. Control aggregates, with heart and neural retina dissociated and co-aggregated simultaneously, also showed heart internal and neural retina external. No effect of length of aggregation time could be detected with this pair of tissues. When pigmented retina cells were allowed to aggregate 6 or 20 hours before addition of heart cells, the cells were in the same final positions as in control aggregates, namely heart external and most pigmented retina cells internal. The only position reversal occurred when heart cells were given 6 or 20 hours to aggregate before addition of pigmented retina cells, which now took up all external positions. This position reversal could result from the heart cells becoming more adhesive with time in culture.

Pteridine eye pigment, indicative of the activity of theor ⁺-allele, was observed inor/or larvae ofPlatynereis, derived from transplantedor ⁺/or oocytes. These heterozygous oocytes had grown up inor/or hosts, themselves deficient in pteridine pigment synthesis. It is therefore concluded that theor ⁺ gene product, responsible for pteridine pigment synthesis in theor/or larvae, had been synthesized by the oocyte genomes.

For causal analysis of morphogenetic systems a device has been developed (Fig. 1) which achieves a well-defined and stable temperature gradient up to 80° C/mm inside small objectsin vivo. The technique requires that the objects are embedded in aqueous agar of 3% (Difco, Detroit/Michigan). By means of an inverted microscope time-lapse cinematography of the objects can be carried out simultaneously.