Wilhelm Roux Archiv Fur Entwicklungsmechanik Der Organismen最新文献

Using transplantation techniques it was shown that immature and supposedly mature stages of fat body from the larvae ofDrosophila melanogaster do not lyse rapidly in the lytic, internal environment of the young adult. In the younger tissue the protein granules (probably lysosomes) were just beginning to form, whereas in the older tissue the protein granules were at a maximum level. In both cases the implanted tissues became steadily smaller independently of the environment. The decrease in implant size was interreted to mean that the cells were lysing, since the average cell size did not change, and since many cells appear cytologically degenerate. However, the estimated rate of cell loss was much slower than in the case where the cells pass through metamorphosis. Some of the immature cells produced relatively high amounts of protein granules independently of the environment. Although the protein granules are at a maximum amount in both stages, it would appear that additional development must be required for the cells to become susceptible to the lytic environment of the young adult.

The number of nematocytes in the tentacles and in the ectoderm of the body-column ofHydra attenuata Pall. shows a great variability. The variability of the nematocytes in the tentacles is manifested, not only if different individuals of the same clone, but also if various tentacles of the same polyp are compared. 2. The percentage of the different types of nematocytes in the tentacles and in the body-ectoderm shows a greater stability than the absolute numbers. A comparison of the percentage of differentiated nematocytes of the body-ectoderm with those of the tentacles shows that in these two regions of the polyp the different types of nematocytes are differently distributed. 3. By a combined chemical and mechanical stimulation of the tentacles, 90% of the stenoteles are discharged unlike the isorhizas and desmonemes, which cannot be brought to explosion under the same conditions. 4. The reaction of the polyp following the selective discharge of stenoteles shows three different phases: a) As a first, short-term reaction to selective discharge, differentiated stenoteles already present in the body-ectoderm move into the tentacles. b) In a second phase, the synchronous mitotic divisions of the already determinated groups of stenotele-nematoblasts are interrupted to enable earlier differentiation. c) In a third, long-term reaction, the production of new stenoteles is increased. This increased production occurs on one hand by supplementary determination of interstitial cells to stenotele-nematoblasts, and on the other hand by supplementary mitotic divisions, i.e. by increasing the number of nematoblasts per group. 5. The intense discharge of stenoteles has two effects on the desmonemes: It causes an increased number of differentiated desmonemes already present in the body-ectoderm during the discharge of stenoteles to migrate into the tentacles as well as an increase in the production of nematocytes of this type. 6. Neither the production nor the migration of the isorhizas are influenced by the discharge of stenoteles. 7. The times of differentiation of the three types of nematocytes are: Isorhizas 1-3 days, desmonemes 3-4 days, stenoteles about 6 days. 8. The variability of the nematocytes in the tentacles and in the ectoderm of the bodycolumn, the moment of determination of the interstitial-cells differentiating into nematoblasts as well as the co-ordinated behaviour of stenoteles and desmonemes are discussed.

Wild-type nuclei, taken out of cells from five regions of early gastrula embryos, were implanted singly into unfertilizedy w sn ³lz^50e eggs ofDrosophila melanogaster. The different types of nuclei initiated development with nearly equal frequencies of about 60%. 2.9% of the 1073 nuclear transfers developed as far as one of the three larval instars, and one reached the pupal stage.All individuals showed stage-specific patterns of defect. Most of these abnormalities were probably due to some inevitable damage caused by the implantation procedure such as disarrangement of the internal egg morphology and loss of peripheral egg substance. The proportions of individuals arrested at different embryonic and larval stages were similar for the five nuclear groups.Fertile imagos, descendants of all five types of donor nuclei, were produced via germ-line mosaics in two ways: (1) Pole cells of nuclear-transplant blastoderm stages were implanted into the pole cell region of host blastoderm eggs. (2) Gonads were taken from nuclear-transplant larvae and implanted into host larvae. In both cases gametes developed from the transplants as could be recognized from the genotypes of their progeny. By means of suitable crosses it was possible to get clones of flies whose large chromosomes were descended from the chromosomes of only one transplanted nucleus, that is, each clone was the descendant of one somatic nucleus. The data presented show that the nuclei remain omnipotent until the early gastrula stage.

From our previous work we have put forward the hypothesis that cholinesterase activity in embryonic cells is related to morphogenetic movements. Therefore, the locomotory behavior of mesenchymal cells differentiating into cartilage by passing through a phase of Cholinesterase activity was analysedin vitro.Mesenchymal cores of chick limb buds stage 23/24 were partially disaggregated and cultured in plastic tissue culture dishes (Fig. 1). Within 31/2 to 5 days aggregates of mesenchymal cells differentiated into cartilage nodules surrounded by myoblasts (Figs. 2, 3 and 5). The cartilaginous nature of the nodules was confirmed by electron microscopy (Figs. 6 and 7). During the culture period serial photographs (24×24 mm) were taken (Tables 1-3). After formalin fixation the histochemical Cholinesterase reaction was carried out inside the culture dishes. Positive and negative cells were identified in the live serial photographs and their locomotory behavior was analysed.Initially the cells behaved like fibroblasts. Movements were regulated by contact inhibition, resulting in radial outward migration within the mesenchymal aggregates. In this first phase of development there was no cholinesterase activity. After 12 to 48 hours in culture however ChE-positive cells could be detected. Positive cells, appearing within a monolayer, detached from the bottom of the culture dish and crawled onto neighboring cells (Figs. 8a and b). In the periphery of the aggregates radial outward migration slowed down considerably. In the center short non-directional movements of positive cells could be observed, frequently leading to overlayering of cell bodies.In the third stage of development the ChE-positive cells stopped moving and transformed into cartilage cells (Fig. 9a and b). Finally, ChE-activity disappeared from the differentiated cartilage cells.From the difference in locomotory behaviour of negative and positive cells it is concluded that the appearance of Cholinesterase is accompanied by a change in the adhesive properties of the cells. An increase in cell adhesiveness enables the ChE-positive cells to detach from the bottom of the culture dish and to establish a new equilibrium of contact inhibition inside the cellular aggregates. This seems to be a prerequisite for the secretion of extracellular matrix and development of firm cell contacts. In vivo cartilage differentiation presumably also starts with an increase in cell adhesiveness in the presumptive cartilage cells. This provokes pseudopodial rearrangements leading to the condensation and demarkation of the cartilage anlagen. The change in adhesiveness is accompanied by Cholinesterase activity.

1. The egg of the Chironomid midgeSmittia spec. has been studied by light and electron microscopy. The present paper describes the fine structure of the anterior and posterior pole regions before pole cell formation. These regions were selected because of their functional involvement in body pattern determination and pole cell formation. 2. In the anterior cytoplasm (region I), 3 subregions can be recognized. A thin outer layer (Ia) which resembles the more equatorial periplasm (region II) but contains fewer organelles, covers a layer rich in mitochondria (Ib). This in turn borders a central cone of cytoplasm (Ic) which protrudes into the anterior face of the yolk endoplasm and frequently contains a cytaster-like structure but no chromatin. 3. The posterior cytoplasm (region III) includes a germ plasm or oosome similar to the type found in other lower dipterans. It is lens-shaped and contains a 3-dimensional network of electron-dense material. This material is probably granular, but may appear fibrous due to the spatial arrangement of the granules. 4. A series of organelles of multivesicular or lysosome-like appearance is described. These may be involved in the formation or utilization of proteid yolk. 5. Special structures or organelles restricted to the anterior pole region were not found. This might indicate that the role of this region in the switch from head formation to tail formation after UV irradiation could be due rather to differences in quantity or arrangement of ubiquitous structures than to qualitative differences between this and other egg regions. However, qualitative singularities cannot be excluded. They are obvious in the posterior pole region which contains the oosome.

The ability of dissociated cells to reaggregate, grow in culture (in vivo) and differentiate cuticular structures following increasing doses of X-ray radiation has been studied.At low doses (up to 5 Kr) reaggregation, but not cell viability, is affected. The reaggregation ability of irradiated cells is improved with increasing time between irradiation and aggregation and can be rescued by mixing irradiated and non-irradiated cells.On the contrary, growth and cell differentiation seem to be cell autonomous events. At doses between 5 Kr and 8 Kr cell proliferation is impaired, and after doses over 10 Kr reaggregates show a "negative growth." The differentiation of cuticular structures, such as chaetes and trichomes, show a different X-ray sensitivity.A unifying interpretation of these results is outlined in the discussion.

The organ culture technique was used for the study of early cytodifferentiation in explanted rat and mouse embryonic shields. After 15 daysin vitro the main tissues were differentiated in explants. The full differentiation depended on the presence of homologous serum in the culture medium. 95% oxygen in the atmosphere was either deleterious or without measurable effect if introduced from the beginning or toward the end of the cultivation period, respectively. Some chemically defined media supported the development for only a limited time span during the initial period of cultivation.

The regeneration (organogenesis was studied by Emig, 1972 a, b) of Phoronida can be divided into three phases: the first one, cicatrisation, is characterized by a provisional mesodermal scar-tissue, later the old epidermis cover this scar-tissue. The regenerating blastema, second phase, takes place by cellular dedifferentiation processes; each germ layer (ectoderm, mesoderm, endoderm) regenerates itself from its own elements. One exception only seems to be oesophagel regeneration by "metaplasia" of the prestomacal cells during the asexual reproduction. The differentiation of the amputated structures (third phase) appears submitted to the inductive influence of the mesoderm and to the trophic action of the nervous system (especially the epithelial plexus). The polarity in regeneration sets a problem in Phoronida.

First part: 1. A deep freezing technique has been developed inDrosophila melanogaster which makes it possible to freeze (1) imaginal discs, (2) blastemas of imaginal discs which have been culturedin vivo and (3) embryonic neoplasms. 2. The suitability of differentsalt solutions for our freezing medium has been tested. It is clear that salt solutions containing organic additives are more suitable than are pure ones. It remains to be determined if, in addition to glycerol, the added sugars also act as freezing protectives. 3. Glycerol as a freezing protective (i.e., cryoprotective) is much better than Dimethylsulfoxide (DMSO) since it was shown not to be toxic to insect tissue. 4. In either the presence or the absence ofprotein in the freezing medium the imaginal discs survive the freezing process. However, without protein the tissue becomes sticky which makes successful transplantation virtually impossible. When the concentration of protein is high (6 mg/ml) in a 10% (v/v) glycerol-freezing medium, the protecting effect is considerably reduced. In contrast, a 10 % (v/v) DMSO-freezing medium requires such a high concentration of protein in order to reduce the toxic effects of the DMSO itself. As protein components, both Fetal Calf Serum (FCS) and Bovine Serum Albumin (BSA) are possible. However, since the concentration of protein in FCS is high and, in addition, the correct dose of protein cannot be measured out, the purified protein BSA is more suitable. 5. The optimalfreezing-velocity for our tissue is 1° C/minute. Thethawing-velocity is 100° C/ minute. 6. The freezing process has no detectable effect on determination and differentiation, nor ontransdetermination.

Second part: 7. The suitability of the technique for freezing imaginal discs has also been tested withlarval ovaries ofDrosophila melanogaster. 8. The normal practice of dipping imaginal discs directly into the freezing medium cannot be applied to larval ovaries. Specifically, under these conditions the membrane of the larval ovary is damaged. Due to this osmotic shock the processes of freezing and thawing lead to the loss of cells and eventual death of the larval ovary. 9. Osmotic shock is not observed if the larval ovaries are stepwise transferred to progressively higher concentrations of cryoprotective in the freezing medium. 10. As a function of the genotype, between 66 and 74% of the larval ovaries survive the freezing process. 11. Reimplantation of the larval ovaries into larval hosts is decisive for the effective success of the freezing method. However, there is virtually no difference in the subsequent development of either freeze-treated or untreated implants. 12. Transplanted larval ovaries connect to the host oviducts with a certain probability which is related to their genotype. In any case, donor ovaries, freeze-treated or untreated, produce on the average much less offspring than do host ovaries. 13. The suitability of the newly d

Only when a part of the prostomium remains in situ does complete anterior regeneration take place.The course of caudal regeneration is the same both in males and females whether they have their prostomia in situ or not. The more segments are amputated the more will be regenerated.The amputation of posterior segments which releases the regeneration, or regeneration itself, may influence the sex of regenerating worms for a short time.