Wilhelm Roux Archiv Fur Entwicklungsmechanik Der Organismen最新文献

1. The fluorescent antibody method was used to study the first appearance of delta-crystallin in the lens rudiment of the chicken embryo, in relation to the cell cycle. At the beginning of lens invagination a few cells, with their nuclei in a basal position, displayed fluorescence. The percentage of cells with a positive reaction increased steadily, but it was not until invagination was well underway, about 3 hours after its start, that fluorescence was seen in dividing cells. It was concluded that in this system cell replication and synthesis of specific protein are not mutually exclusive. 2. Because the number of hours passing by before the appearance of fluorescent mitoses was about equal to the previously calculated duration of the G-2 phase of the cell cycle it follows that crystallin production becomes detectable in the late S- or early G-2 phase. Observations on the cellular shape, which is a function of cell cycle phase, at the time that cells first reacted with the fluorescent antibodies agree with this interpretation. 3. The suggestion is made that the inductive influence of the optic cup on the lens primordium may primarily be exerted during the DNA synthetic phase of the presumptive lens cells.

The effects of BrdU (3×10^-4 M) on morphogenesis of the chick embryo explanted at the definitive streak stage and cultured for 24 hours were studied. Compared to controls treated embryos often showed (1) an open neural tube and (2) less numerous somites. Heart development was not significantly affected by BrdU. The damage caused by BrdU was not permanent, i.e., the embryos retained the ability to undergo fairly normal morphogenesis when, after 4-5 hours of BrdU treatment, they were subcultured on a medium with excess thymidine.

Generation time, duration of cell cycle phases and growth fraction were measured for three tissues: telencephalon, anterior limb-bud mesenchyme and intestinal epithelium.By rearing young larvae at different temperatures (12, 16 and 24° C), it was demonstrated that: cell cycle duration (T) and the duration of S, G₂ and M phases are shorter at higher temperature; the G₁ phase is characteristically lengthened or shortened, depending on the tissue concerned at a given stage, the growth fraction (CP) is characteristic for each tissue, and does not vary with temperature the sensitivity to temperature conditions is also characteristic for each tissue; anterior limb bud mesenchyme is the least sensitive. Ageing and differentiation of cell populations during larval life and natural metamorphosis (at the constant temperature of 16° C) lengthen the generation time (T) and the duration of S, M and G₁ phases; simultaneously the growth fraction decreases. But at the metamorphic climax, the growth rate of some tissues (telencephalon, secondary intestinal epithelium) is suddenly and temporarily increased, as a result of both a shortening of T and an increase of CP. On the contrary, other tissues (primary intestinal epithelium) no longer proliferate, and collapse. These different modifications to the different organs seem to be related to variations in the amount of thyroxine in the circulating blood. They can be considered as one of the aspects of the differential tissue sensitivity to thyroxine.

The mechanism of evagination of isolated imaginai discs has been studiedin vitro. Pro-, meso-, or metathoracic leg discs were obtained from late 3rd instarDrosophila larvae and cultured in the presence or absence of α-ecdysone and of various substances (cytochalasin B, concanavalin A, neuraminidase, trypsin) known to affect the cell membrane and morphogenetic movements in vertebrates.In the presence of cytochalasin B, evagination was reversibly inhibited. Cytochalasin B apparently does not act on intracellular microfilaments, which could not be detected in the disc cells. It does not prevent ecdysone from being fixed in the cells. It probably modifies the physico-chemical properties of the plasma membrane, precluding the change in cell shape which is required for evagination.In the presence of concanavalin A, which binds specifically to hydroxyl groups of D-mannopyranose or D-glucopyranose, evagination was irreversibly inhibited. The inhibitory effect could however be neutralized by the addition of α-methyl-D-glucopyranose in the medium or prevented by pre-treating the discs in a 0.1% trypsin solution for 2 min.In the presence of neuraminidase, discs evaginated normally under the influence of α-ecdysone; in a few cases, neuraminidase caused partial evagination in the absence of moulting hormone.After treatment by a 0.1% trypsin solution for 2 min, discs evaginated normally under the influence of the moulting hormone; whereas in the absence of ecdysone, evagination was never observed. In the latter case, evagination could however be obtained by a mechanical pull.When normal evagination was inhibited by one of the tested substances, cells did not secrete either a pupal or an imaginai cuticle and did not form any integumentary differentiations.It is concluded that change in cell shape during evagination is related to changes of the cell membrane. The alterations of the physico-chemical properties of the cell membrane, which are required for evagination, are probably caused, during normal development, by the moulting hormone.

1. The joint of the fore-wing inLymantria is described and compared with the joints of other lepidoptere. 2. The morpho- and histogenesis of the joint elements are investigated. The tegulaanlage can be seen at the end of the last larval period, as a double tissue. 3. After extirpation of parts of the wing-anlage and implantation of this section into the dorsum of the same caterpillar at the 9th day of the last larval stage, the extirpated tissue cannot be replaced. These parts maintain their state of determination when isolated and differentiate the elements lacking in the joint of the butterfly after molting of the imago. 4. The parts of the tegula in the joint and the implanted fragment are measured. The sum of these two measurements is always lower than the 100%-value of the tegula of the opposite, untreated side. 5. By extirpation and implantation the prospective joint elements on the wing disk can be determined. 6. Apart from a short delay resulting from the narcosis and the shock following the operation, the last larval stage is not significantly prolonged.

The migratory properties of hydra cells within the tissue were studied. The extent and direction of cell migration were examined in budding, non-budding, and regenerating animals. Nematocytes and a small number of single big interstitial cells (the multipotent interstitial cells) actively migrate preferentially in an apical direction. Basal migration of these cells occurs only when a bud is present and, in which case, the cells migrate into the developing bud. The regeneration of the hypostome and tentacles does not affect cell migration in either direction, except for apical migration of stenotele nematocytes, which was markedly reduced.

1. The oxygen consumption of normal and half-embryos ofXenopus laevis was measured by the automatic electromagnetic diver respirometer. 2. The rate of morphogenetic development of dorsal, left, and right half-embryos was found to be the same as in whole embryos but, in conformity with earlier observations, the development of ventral half-embryos is blocked. 3. Respiration of dorsal, right, and left half-embryos was found to be approximately half the normal, except in the initial cleavage period. Respiration of the ventral half-embryos, on on the contrary, failed to increase substantially by the time of gastrulation. 4. Our findings suggest a strict correlation between oxygen (and energy) consumption and epigenetic work.

Observations have been made and experiments performed to investigate the colour of pupae inPapilio machaon L. andPieris brassicae L.InP. machaon brown pupae are nearly always formed except when the pupation site is the foodplant, when nearly half the pupae are green. Switching experiments showed that the sensitive period was just before pupation and that the colour and texture of round foodplant stalks had a significant influence in producing green pupae.In the Cambridge stock ofP. brassicae used all non-diapause pupae are "brown" (including yellowish, ochreous, greyish forms), all diapausing pupae green. The background on which pupation occurred had no significance, nor did the photoperiod immediately preceeding pupation.The colour could, however, be changed by the food used; on artificial diet the pupae are blue or turquoise. This effect could not be reversed by the addition ofβ-carotene to the diet, as might be expected. Attention is also drawn to the fact that at least one pupal colour is known to be genetic, and the possibility that the green/brown relationship with diapause in the CambridgeP. brassicae stock may be due to the rearing conditions used.

1. The regulative ability of the regeneration blastema of the newt limb (Notophthalmus viridescens) was tested by operationsin situ. Either the anterior, posterior, dorsal, or ventral half of the blastema was removed at various stages during regeneration. 2. All blastemas operated on prior to the stage of four early digits showed a delay in reaching the subsequent stages of regeneration. 3. The blastema is capable of extensive regulation in the anterior-posterior and dorsoventral axes even after many of its cells have begun to differentiate. 4. Early digital stages of regeneration were found to be defective in regulative ability. Additional skeletal elements were present in limbs which had been operated on at the stage of three early digits. Supernumerary digits as well as additional skeletal elements were present in limbs which had been operated on at the stage of four early digits. Removal of the posterior half of the regenerate at one of these late stages resulted in more severe abnormalities than did removal of the anterior half. 5. Either the anterior or the posterior half of a mature limb was removed back to the level of the wrist. In several cases, an almost complete autopodium developed alongside the remaining half autopodium. 6. Removal of half of a regenerate at digital stages gave results similar to those obtained following removal of half of a mature limb. 7. The results are discussed in the context of other experiments on regenerating limbs, and of experiments on other developing systems. It is concluded that amphibian blastemas in common with a number of other systems can develop according to the presumptive fates of their cells, or they can regulate when they are given the opportunity for growth and cell division.

The posterior pole ofDrosophila melanogaster eggs was irradiated with ultraviolet light of 253.7 nm wavelength; different batches were irradiated at different times after oviposition, ranging from less than 10 mins to 125 mins. Two different experiments were run at different dose levels: 280 μW/mm² and 530 μW/mm². A differential response to irrariation was observed in relation to the age of the treated eggs. Embryo mortality increased with egg age in both experiments (Fig. 1).No differential effects onlarval mortality were found in egg batches irradiated between 15 and 95 mins of age in either experiment (Fig. 3).The incidence ofsterility in the survivors was higher when the eggs were irradiated before 55 mins or when pole nuclei were present. The overall incidence of sterility was much higher in the high-dose experiment (Fig. 4).Sterility is considered as a measure of damage to germ cell precursors, most probably involving RNA. On this basis the probability of the affected RNA being messenger RNA stored in polar granules is discussed.