Wilhelm Roux Archiv Fur Entwicklungsmechanik Der Organismen最新文献

The effects of a number of inhibiting agents on the isolated hatching enzyme of the trout,Salmo gairdneri, have been studied. The enzyme differs from the family of proteases and esterases with serine at the active site, as no inhibition was observed in the presence of PMSF, TPCK, and TLCK. Inhibition is feasible by a number of chelating and ion-metal complexing agents. The results of the inhibition studies indicate that the enzyme belongs to the group of metalloproteases, in contrast to the hatching enzymes of the amphibians and certain moths.

In the telotrophic meroistic ovary ofDysdercus intermedius Dist. the oocyte is provided in a previtellogenic state with RNP-particles synthesized by trophocytes, transported in nutritive cords and deposited in oocytes. Ribosomes prepared by differential centrifugation from trophic tissue and mature eggs were fractionated into RNP-particle classes using a linear sucrose gradient. Particles were labeled by injecting radioactive RNA-precursors. Two hours later in trophic tissue besides 80 s monosomes and ribosomal subunits labeled RNP-particles are detected sedimenting slower than small ribosomal subunits (10-40 s). They are not transferred into the polyribosomal protein synthesizing complex of trophocytes. The ribosome fraction from eggs laid 8 days after injection of radioactive precursor contains the same labeled RNP-particle groups as the trophocytes. Because of the special character of telotrophic meroistic insect ovary (no detectable synthetic activity of oocyte nuclei during the growth phase, no contribution of high molecular weigth RNA from follicle cells to oocyte) these particles in the fresh laid bug-egg can be considered as products which are synthesized in trophocytes and therefore as depot-forms of maternal information for early embryonic protein synthesis.80 s monosomes contain exclusively rRNA (28 s and 18 s). In the slow sedimenting RNP-particles RNA was detected showing the following mRNA-characteristics: 1. a heterogenic molecular size with maximum at 7-9 s (proved by gelelectrophoretic analyses of radioactive labeled RNA isolated from particle groups), 2. a high content of Poly A-segments (proved by retention on nitrocellulose filters), 3. a stimulating capacity on amino acid incorporation in a cell-free protein synthesizing system.In a homologous cell-free system composed of bug components native mRNP-particles (10-40 s) from eggs and nurse cells cause an inhibition of amino acid incorporation into proteins. For this inhibitory effect proteins are responsible which dissociate from the particles in a medium of high ionic strength (0.5 M KCl). Under the same experimental conditions factors are dissociated from larval RNP-particles which show a stimulating effect on amino acid incorporation. Therefore inhibitory factors are thought to be structural or accessory specific components of maternal mRNP-particles. M-RNA from egg particles freed from inhibitory factors can be translated by specific factors which are detected-like the inhibitors in the ribosomal wash fraction.

Dissociation and reassociation experimentsin vitro were carried out to investigate the differentiation potency of chick allantoic endoderm under the influence of digestive tract mesenchymes. 1. The allantoic endoderm, when cultured alonein vitro, shows no differentiation whatsoever. 2. The allantoic endoderm, when cultivated combined with the mesenchyme of oesophagus, can differentiate into a stratified cuboidal epithelium, similar to that of the embryonic oesophagus. 3. Cultivation of the allantoic endoderm combined with the proventricular mesenchyme causes differentiation of cylindrical epithelium and glands, which are characteristic of the embryonic proventriculus. 4. The combination of the allantoic endoderm and the gizzard mesenchyme results in the differentiation of pseudostratified columnar epithelium, the cells of which possess glycogen granules like those in the normal embryonic gizzard. 5. If the allantoic endoderm is cultured on the mesenchyme of the small intestine, the endodermal cells are converted into simple columnar epithelial cells similar to those of normal embryonic small intestine. 6. The competence for the heterotypic development of the allantoic endoderm appears to be a function of a developmental time sequence: it is highest in the youngest (3-day) allantoic endoderm, and gradually lost in older embryos. 7. In all combinations tested, there appear goblet cells in the epithelium when the explants are cultured more than 10 days. These cells are never observed in intact oesophagus, proventriculus and gizzard, whether in normal development or in culture.

The investigations were performed with the eggs of the sea urchin speciesSphaerechinus granularis Lam. They were kept at 22° C under continuous aeration for up to 45 hours with stirring to compensate for sedimentation. 1. The change in DNA content, 2. the change in DNA dependent DNA polymerase activity, and 3. the change in DNase activity with time have been evaluated. 1. DNA Content of Embryos. The DNA content of the embryo development was determined by two different methods. Before and immediately after fertilization DNA content has been found to be 1.7±0.5·10^-10 g per egg. This amount is about 100 times higher than in diploid nuclei. Three periods with different rates of DNA synthesis may be distinguished: a) the first one, lasting from fertilization to about the time of the volume maximum just before the onset of gastrulation with an average rate of synthesis of 1.2·10^-10g DNA per minute per embryo; b) a second one, lasting from then on to the gastrula stage with a lower average rate of synthesis of about 0.7·10^-12 g DNA per minute per embryo; c) a third one, starting from the gastrula stage up to the experimental end point in the pluteus stage. The rate of synthesis in this case is 2.3·10^-12 g DNA per minute per embryo. On a relative base the rates of synthesis are 100∶58∶192. The cytoplasmic, extramitochondrial DNA persists through the stage of the first period of the embryogenesis, up to the blastula stage. The amount of extranuclear DNA increases in the first 6 hours of embryo development; then the cytoplasmic DNA disappears. 2. DNA Dependent DNA Polymerase Activity. The DNA polymerase has been isolated from embryos. Its activity has been determined in relation to the activity of the total embryo as well as per embryonic cell. The polymerase activity is much higher at the start of the development than in later stages, reaching a minimum in the blastula stage, the time at which cytoplasmic DNA has been exhausted. In the subsequent period the polymerase activity parallels the rate of DNA synthesis in vivo. The level of the DNA polymerase activity per cell remains constant. 3. DNase Activity. The DNase activity has been determined using the Lanthanum-Nitrate-Method. Three distinct maxima were found: A first maximum is reached immediately upon fertilization. The second one coincides with the onset of mesenchyme formation in the blastula, and the third one coincides with the end of gastrulation. The average specific activity is roughly equivalent to about 10^-6 g DNase I per g of embryo. The possibility is discussed that rises in nucleolytic activities may trigger differentiation events in the developing egg. The influence of DNA polymerase activity and DNase activity on in vivo DNA synthesis is discussed.

A method for the organ culture ofDrosophila testes is described which supports the differentiation of primary spermatocytes through the meiotic divisions to elongating spermatids. Autoradiographic and inhibitor studies reveal no evidence for RNA synthesis by developing spermatids ofDrosophila melanogaster; most, if not all, of the RNA required for the differentiation and elongation of sperm is synthesized earlier in the primary spermatocytes. Primary spermatocytes will differentiate into elongating spermatids in organ culture, despite severe (96-98%) inhibition of³H-uridine incorporation into RNA effected by 50 μg/ml 3'-deoxyadenosine. Protein synthesis in spermatids continues to be active in the presence of 3'-deoxyadenosine, but that in growing spermatocytes is severely inhibited.

1. Posterior regeneration of normalNereis diversicolor O. F. Müller includes two stages: regeneration of the pygidium, regeneration of setal segments. Regeneration of the pygidium results from mitotic proliferation of epidermal cells in close proximity to the wound after junction between epidermis and intestinal epithelium at the section plane; correlatively, mesodermal cells accumulate behind the healing area. Pygidial differentiation is precocious and results both from a rearrangement of mesodermal cells inside the blastema and the differentiation of epidermal and mesodermal cells in the area of the future pygidium. Regeneration of setal segments is caused by the association of two different levels in a gradient of antero-posterior differentiation (regenerated pygidium-last segment of the stump); it results from the activity of a narrow undifferentiated area (proliferation zone) which persists just in front of the regenerated pygidium. 2. Externally, posterior regeneration of decerebratedN. diversicolor O. F. Müller consists only of the differentiation of the pygidium. However, an histological study of these regenerates shows a beginning of mesodermal segmentation and parapodial differentiation in the area between the regenerated pygidium and the stump. These observations demonstrate that: the brain plays no role in the activation and division of the blastema cells, at least during the first steps of the regeneration process; the activity of the nervous system, mainly the nerve cord, is not interfered by extirpation of the brain; the differentiation of the pygidium escapes from the control exerted by the brain; the metamerisation of the mesoderm is independent of the growth and segmentation of the regenerated epidermal wall; the absence of regenerated setal segments results probably from the morphogenetic inactivity of the epidermis of the prepygidial area.

The effects on tentacle regeneration inHydra of two DNA-antimetabolites, bromouracil and bromodeoxyuridine, have been studied. Bromouracil inhibits tentacle regeneration inH. vulgaris andH. viridis; bromodeoxynridine inhibits tentacle regeneration inH. vulgaris but notH. viridis over the range of concentrations studied. Thus these two species appear to differ in their susceptibilities to these drugs, and the drugs may have different efficacies in this system.

In the egg ofAcheta domesticus L., peripheral streaming alters the originally equidistant distribution of early (plasmodial) blastoderm nuclei. Nuclei accumulate in the egg region between 10 and 50% of egg length measured from the posterior pole, while in other egg regions the distance between nuclei increases. The crowded nuclei will form the germ anlage proper. As a first step they reduce their volumes considerably. In the present study, whole mounts of eggs separated during cleavage into 2 fragments were scored for nuclei of reduced volume. The results were compared to the capability of similar egg fragments to form complete or partial germ bands.In eggs separated at 30% egg length, most nuclei in the posterior fragment will suffer size reduction and, if development is allowed to proceed, will form complete germ bands. In the anterior fragments, nuclei which normally will participate in head formation are carried backwards by peripheral streaming and accumulate near the rear end of the fragment. However, their volumes do not decrease, and no germ bands parts will be formed in such fragments during further development; instead, the blastoderm is converted exclusively into extraembryonic covers. These results show that the streaming and crowding of nuclei as such are not sufficient to induce size reduction and the switch towards germ band formation. It is concluded that for these changes to occur some additional influence is needed. This should in normal development be exerted by the posterior egg region which was separated from the anterior fragment in the experiment.

The injection of farnesyl methyl ether into last instar larvae results in preventing metamorphosis completely (production of a supernumerary larva) or partially (production of adultoids). The degree of this inhibition depends on both dose and moment of injection of the juvenile hormone-mimicking compound. A critical period beyond which the injection will be without effect on the larvae was determined.The external morphology of several organs (mask, wing sheaths, legs, tergites and anal appendages) will be described, on supernumerary larva as well as on different types of adultoids. All these organs show various degrees of sensitivity to injected juvenile hormone-mimicking substance.These results are discussed on the basis of both "prothoracotropic" and juvenile hormone activity of farnesyl methyl ether.

The femaleTenebrio molitor genital anlage differentiates from a part of the sternal and abdominal integument of the larva. This epidermal tissue shows a very high regulative capacity during the whole life of the larva. This capacity appears only within the regulative area. The presumptive genital epidermis is composed of labile, morphogenetic fields. It shows however a determined axis of polarity controlled by adjacent abdominal tissues forming a part of the regulative area.