Hadar Emanuelsson

Pheromone reception in the males of the amphipod Gammarus duebeni Lilljeborg

Experiments were carried out to test whether water transport of pheromone from female to male takes place in the amphipod Gammarus duebeni. In G. duebeni sexual dimorphism occurs im presumed chemosensory receptor mechanisms of the 2nd antenna, which carries calceoli in the male. Sexually mature females were fed 3H-acetyl-glucosamine-labelled trout liver and became highly radioactive. Males were exposed to water containing such females. They reacted by swimming to the double net partition separating them from the females. After I to 1 h exposure scintillator measurements on males showed about 1000 times higher radioactivity per mg body weight in the 2nd antenna than in the remainder of the body. Light microscope autoradiography showed selective labelling of calceoli sites. This was taken to indicate that a 3H-labelled sex pheromone from the female had reached receptors in the male calceoli.

Effects of serotonin and serotonin antagonists on chick embryogenesis

SummarySerotonin and some selected substances known to interfere with its formation (diethyldithiocarbamate) and function (Catron®, 5-methyltryptamine, promethazine) were tested for their ability to affect chick embryo morphogenesis during the first 48 h of development. To detect possible differences in sensitivity between the successive morphogenetic events taking place during this period, the treatment was begun at successively more advanced stages corresponding to embryo ages of between 4 and 30 h incubation. In all cases, the treatment was terminated at an embryo age of 48 h incubation. The treatment was performed both in ovo and in vitro.With some exceptions, the substances induced malformations of the same characteristic types. The developmental processes subjected to disturbances included blastoderm expansion, primitive streak formation, neurulation with brain formation, and somitogenesis. At the cellular level, the malformations can be traced to delayed yolk degradation, impaired formation and function of microvilli, and impaired ability of the embryo cells to change shape.All of the tested chemicals can be expected to interfere with intracellular levels of serotonin. They obviously interfered with decomposition of the yolk granules, recognized centres for intracellular serotonin formation and we therefore conclude that the observed morphogenetical disturbances are ultimately due to impairment of the endogenous serotonin formation. We suggest that, in morphogenesis, serotonin primarily promotes the activity of microtubules and microfilaments.

Electronmicroscopical observations on yolk and yolk formation in Ophryotrocha labronica LaGreca and Bacci

SummaryIn Ophryotrocha labronica LaGreca & Bacci mature yolk granules are found only in the ovocyte. Other typical yolk elements are lipid droplets, small vesicular bodies, multivesicular bodies and dense bodies. The two last-mentioned also appear in the accompanying nurse cell and from there obviously pass over unchanged into the ovocyte through a specific intercellular bridge, the fusome.The mature yolk granules are considered as aggregates of mitochondrial, endoplasmic and Golgi material, to which also is added pinocytotically incorporated external material. Mitochondria apparently play a fundamental role in the process, as the multivesicular bodies, most likely the direct precursors to the yolk granules, in all probability represent transformed mitochondria.Labelling with 3H-thymidine during vitellogenesis reveals presence of DNA in the yolk granules. From the labelling pattern, which shows DNA-synthesis both in the ovocyte and the nurse cell nucleus, it is concluded that the labelled material present in the cytoplasm of both cells — most of it in yolk granules and dense bodies — is of nuclear origin. The possible mitochondrial nature of yolk granule DNA is discussed.

Presence of serotonin in early chick embryos

With biochemical analysis and with autoradiography based on injection of 5-[3H]hydroxytryptophan, it was possible to demonstrate the presence of serotonin (5-hydroxytryptamine) in early chick embryos as early as the pre-streak stage. The biochemical analysis which covered the early developmental period (0.5-6 days of incubation) revealed an elevated concentration of serotonin at gastrulation; from then it stayed at a lower and fairly even level. Autoradiographs of embryos at the pre-streak stage, the primitive streak stage, the head fold stage and the 4-6 somites stage indicated the presence of serotonin in intracellular yolk granules and in cell nuclei. Moreover, the amine appeared associated with microfilaments and microtubules, particularly in developing neural cells. Notably the elevated concentration of serotonin at gastrulation, but also the intracellular distribution of the amine during early organogenesis, indicates a prominent role for it in cell-shape changes and morphogenesis in the early chick embryo.

Localization of serotonin in cleavage embryos of Ophryotrocha labronica La Greca and Bacci

SummarySerotonin 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.

Pheromone Transport and Reception in an Amphipod

Sexual dimorphism in the second antennae of the amphipod Gammarus duebeni Lilljeborg is connected with the reception in the male of a female sex pheromone transported through the water. Investigations on tritium-labeled specimens were carried out with scintillator and autoradiographic techniques.

Effect of cortisol on human fetal lung in organ culture

SummaryHuman fetal lung tissue obtained during the second trimester was cultured as organ culture with or without cortisol. The effect of cortisol on the phospholipid metabolism, as related to the appearance of osmiophilic lamellar bodies and the localisation of newly incorporated choline, was studied. In cortisol-treated expiants, the concentration of saturated lecithins and the incorporation of (Me-3H)-choline into saturated lecithins increases significantly concomitantly with an increased number of osmiophilic lamellar bodies. The labelled choline is predominantly associated with these bodies. The obtained results indicate that cortisol accelerates the synthesis of pulmonary surfactant in the human fetal lung as early as in the second trimester.

Essential role of the polyamines in early chick embryo development

We are in an age increasingly shaped and inflected by digital and networked technologies, which can act to augment, amplify or disrupt existing discrimination, exclusion and inequality. Using the Feminist Principles of the internet as a framework, this article examines the different facets of the intersection between digitally networked technologies and feminism at the areas of economy, autonomy and data, as well as movement building. It calls for the recognition, exploration and participation of diverse actors in feminist and women’s movements into making a feminist internet.

Cell multiplication in the chick blastoderm up to the time of laying

Abstract An analysis of cell multiplication in the chick blastoderm during the cleavage-blastular period is given, based upon observations on normal blastoderms and representing all stages up to the unincubated blastoderm. This material has further been completed with observations on corresponding blastoderms, supplied in ovo with 3 H-thymidine. Three separate developmental phases can be distinguished during the actual period: an initial phase of synchronous divisions ending in blastoderms of about 30 cells, a succeeding increasingly asynchronous phase with rapidly decreasing mitotic index which from about the 10,000-cell stage passes over into the third phase, characterized by a relatively stable mitotic index of about 4 per cent. During the initial phase the big blastodermal nuclei display aberrant divisions, and incorporation of 3 H-thymidine is slight or absent. From the second phase on thymidine incorporation in the nuclei is increasingly obvious, and calculated labeling indices permit rough estimations of the average generation time of the cells. Multinuclear cells have been observed in the blastoderms during the second and the third phase; mononuclear cells with very big nucleus are also a characteristic feature, especially in the blastoderms of the laying stage.

Effects of polyamine limitation on nucleolar development and morphology in early chick embryos.

Inhibition of polyamine synthesis in early chick embryos by in ovo treatment with DL-alpha-difluoromethylornithine (DFMO), injected beneath the blastoderm after 5 h of incubation, permanently blocks post-gastrular development. After the first day of polyamine limitation, the embryos possess a thickened primitive streak. Further morphogenesis is blocked and the ectoderm and mesoderm are condensed around the streak. There is obvious suppression of nucleolar formation in 24 h DFMO-treated embryos. In the mesoderm obliquely in front of Hensens node the frequency of nucleolus-possessing cells is only a few percent lower in DFMO-treated than in control embryos. However, in the same area the frequency of mesoderm cells possessing multiple nucleoli is about 50% lower in the polyamine-depleted embryos. At the ultrastructural level, mesoderm cells from 24 h DFMO-treated embryos show a reduction of the fibrillar component of the nucleolus with a resulting segregation of the nucleolar material. Our data indicate that stimulation of polyamine synthesis is an obligatory step in the differentiation of epiblast cells into mesoderm cells.