Zebrafish Dynamin is required for maintenance of enveloping layer integrity and the progression of epiboly

Epiboly, the first morphogenetic cell movement that occurs in the zebrafish embryo, is the process by which the blastoderm thins and spreads to engulf the yolk cell. This process requires the concerted actions of the deep cells, the enveloping layer (EVL) and the extra-embryonic yolk syncytial layer (YSL). The EVL is mechanically coupled to the YSL which acts as an epiboly motor, generating the force necessary to draw the blastoderm towards the vegetal pole though actomyosin flow and contraction of the actomyosin ring. However, it has been proposed that the endocytic removal of yolk cell membrane just ahead of the advancing blastoderm may also play a role. To assess the contribution of yolk cell endocytosis in driving epiboly movements, we used a combination of drug- and dominant-negative-based approaches to inhibit Dynamin, a large GTPase with a well-characterized role in vesicle scission. We show that Dynamin-dependent endocytosis in the yolk cell is dispensable for epiboly of the blastoderm. However, global inhibition of Dynamin function revealed that Dynamin plays a fundamental role within the blastoderm during epiboly, where it maintains epithelial integrity and the transmission of tension across the EVL. The epithelial defects were associated with disrupted tight junctions and a striking reduction of cortically localized phosphorylated ezrin/radixin/moesin (P-ERM), key regulators of epithelial integrity in other systems. Furthermore, we show that Dynamin maintains EVL and promotes epiboly progression by antagonizing Rho A activity.     

Growth and distribution patterns of Roseobacter/Rhodobacter, SAR11, and Bacteroidetes lineages in the Southern Ocean

Roseobacter/Rhodobacter and SAR11, affiliated with Alphaproteobacteria, and the phylum Bacteroidetes constitute a large proportion of marine planktonic bacteria, but information about their growth and distribution patterns in the Southern Ocean is scarce. The aim of the present study is to determine patterns in the biomass and productivity of Roseobacter/Rhodobacter, SAR11, and Bacteroidetes groups along the steep temperature, salinity, and organic matter gradients in the Southern Ocean by using catalyzed reporter deposition-fluorescence in situ hybridization and bromodeoxyuridine (BrdU) immunocytochemistry FISH. We found that Roseobacter/Rhodobacter, SAR11, and Bacteroidetes are prominent contributors to total bacterial biomass and production. SAR11 bacteria were the predominant lineage, but their biomass was low in the coldest regions. In contrast, the biomasses of Roseobacter/Rhodobacter and Bacteroidetes lineages were positively correlated with organic matter concentrations. The Roseobacter/Rhodobacter had the highest proportion of BrdU-positive (i.e., actively growing) cells among the three phylotypes at all stations, despite their low abundance. The relative contribution of Bacteroidetes to the total bacterial productivity (number of active cells) was negatively correlated with temperature. These results suggest that the growth and distribution patterns of Roseobacter/Rhodobacter, SAR11, and Bacteroidetes were determined by different environmental gradients (e.g., organic matter concentrations or temperature) in the Southern Ocean.     

Chromosomes of Onchocerca volvulus (Spirurida: Onchocercidae): a comparative study between Nigeria and Guatemala

Chromosomes of Nigerian Onchocerca volvulus were compared with those of Guatemalan O. volvulus. Both parasites had basically the same chromosomal construct (2n = 8, XY type). Autosomes consisted of a pair of large and two smaller pairs. Sex chromosomes were made up of medium sized X chromosome and very small Y chromosome. It was not possible to infer the position of the centromeres.     

Characterization of a neutral ceramidase orthologue from Aspergillus oryzae

Ceramide is an important molecule not only structurally but also regulationally as a modulator of various cellular events. Ceramidase (CDase) are classified into three different types (acid, alkaline, and neutral CDases). Neutral CDase could play an important role in the regulation of ceramide levels in the extracellular space. In this study, we describe the characterization of a neutral CDase orthologue from the filamentous fungus Aspergillus oryzae . The gene encoding the neutral CDase orthologue was cloned and overexpressed in A . oryzae . The purified recombinant enzyme was optimally active at pH 4.0–4.5 and 40 °C. The apparent K _m and V _max values of the enzyme for C12-NBD-ceramide were 3.32 μM and 0.085 μmol min⁻¹ mg⁻¹, respectively.     

Lipid peroxidation and the subsequent cell death transmitting from ferroptotic cells to neighboring cells

Ferroptosis regulated cell death due to the iron-dependent accumulation of lipid peroxide. Ferroptosis is known to constitute the pathology of ischemic diseases, neurodegenerative diseases, and steatohepatitis and also works as a suppressing mechanism against cancer. However, how ferroptotic cells affect surrounding cells remains elusive. We herein report the transfer phenomenon of lipid peroxidation and cell death from ferroptotic cells to nearby cells that are not exposed to ferroptotic inducers (FINs). While primary mouse embryonic fibroblasts (MEFs) and NIH3T3 cells contained senescence-associated β-galactosidase (SA-β-gal)-positive cells, they were decreased upon induction of ferroptosis with FINs. The SA-β-gal decrease was inhibited by ferroptotic inhibitors and knockdown of Atg7, pointing to the involvement of lipid peroxidation and activated autophagosome formation during ferroptosis. A transfer of cell culture medium of cells treated with FINs, type 1 or 2, caused the reduction in SA-β-gal-positive cells in recipient cells that had not been exposed to FINs. Real-time imaging of Kusabira Orange-marked reporter MEFs cocultured with ferroptotic cells showed the generation of lipid peroxide and deaths of the reporter cells. These results indicate that lipid peroxidation and its aftereffects propagate from ferroptotic cells to surrounding cells, even when the surrounding cells are not exposed to FINs. Ferroptotic cells are not merely dying cells but also work as signal transmitters inducing a chain of further ferroptosis.Subject terms: Cell death, Autophagy     

The acquirement of growth ability for third-stage larvae of Strongyloides ratti during the head-passage in the rat

The role of larval passage through the head in the course of the migration of Strongyloides ratti in rats was investigated. Third-stage larvae (L3) recovered from various portions of donor rats were re-injected into the skin, cranial cavity and small intestine of recipient rats to check their ability for further growth. Cultured L3 (L3c) and the L3 recovered from the skin of donor rats (L3s) did not survive in the small intestine after intestinal inoculation. However, intestinal inoculation of L3 recovered from the head of donor rats (L3h) revealed growth to the adult stage. Cultured L3 injected into the cranial cavity of rats also became adult worms in the small intestine. L3 incubated in the cranial cavity for more than 24 h could grow in the small intestine of the recipient rats. These experiments suggest that S. ratti L3 acquire their ability to mature in the small intestine during their migration through the head of rats.