Search PubMed⌕ Search

Biomedical subjects

Y C Hsu

Publications and source records attributed to Y C Hsu.

At least 55 records · Page 3Linked to original sources
PubMed1980

Sequential development and tissue organization in whole mouse embryos cultured from blastocyst to early somite stage.

The development of mouse embryos in culture from the implantation to the head-fold stage was sequentially examined. Our goal was to compare the morphology of embryos grown in vitro to those developed in vivo, published in standard texts, and to delineate the stages involved in the process of tissue differentiation and organization. Mouse blastocysts (stage 6) were collected at 3.5 days p.c. and cultured. Attachment of the blastocysts occurred on the second day of culture (stage 8). Following the collapse of the blastocyst endoderm cells began to migrate and to encircle the inner cell mass. At 2 days in culture the embryonic and extra-embryonic ectoderm became distinguishable and the proamniotic cavity appeared (stage 9). Egg cylinders began to project above the substrate at 2.5 days in culture (stage 10) and to progress through the stages observed in vivo. At 4 days a posterior amniotic fold began to form (stage 11) and was followed at 5 days by the formation of the chorion, the appearance of mesoderm, exocoelom, and head fold (stage 12). At 6 days in culture the embryo had differentiated longitudinally and developed an allantois, blood islands, Reichert's membrane, head process, and primitive streak. At 7 days somites as well as the neural fold and heart were observed (stage 14) and were followed by further differentiation at 8 days (stage 15). These observations indicate that apparently normal embryo development can be maintained in vitro through the early stages of organogenesis, thus providing a unique opportunity for investigating the regulation of early mammalian development.

Animals↗
PubMed1980

Changes in S-phase associated with differentiation of mouse embryos in culture from blastocyst to early somite stage.

Mouse embryos, cultured for 8 days from the blastocyst (stage 5 of Theiler, 1972) to the 10--12 somite stage (stage 13) were labeled at daily intervals with 5 muCi/ml 3H-thymidine for 2 h, sectioned, and processed for autoradiography. The frequency of labeled cells, as well as the intensity of labeling, exhibited a progressive decline during the period of growth of embryos in culture. Endoderm and ectoderm cells were characterized by significant differences in the labelling index and the rate of DNA syntheses. These changes indicate that, during mammalian embryogenesis, the relative duration of the S-phase declines and that the absolute duration of the S-period expands.

Animals↗
PubMed1980

Correlative scanning electron, transmission electron, and light microscopic studies of the in vitro development of mouse embryos on a plastic substrate at the implantation stage.

Correlative scanning electron, transmission electron, and light microscopy were utilized to study the morphogenic events occurring during mouse blastocyst outgrowth and early-egg-cylinder development in vitro. After hatching and attachment of blastocysts on the plastic surface, the blastocoelic cavity collapses as the mural trophoblasts spread and migrate outward. The inner cell mass is covered with a differentiated endoderm on the blastocoelic cavity side and by the polar trophoblasts on the medium side at this stage. As the endoderm-covered inner cell mass proliferates, being physically restricted from further downward expansion by the plastic coverslip and by lack of space in the collapsed blastocoelic cavity, it migrates upward and protrudes into the culture medium in a break between the polar and mural trophoblast cells. Polar trophoblast cells apposed to the base of the egg cylinder continue to proliferate forming the ectoplacental cone. Thus, the early egg cylinder lacking a trophoblast barrier begins inverting its growth pattern from towards the culture dish surface to a more upright position. Egg-cylinder development in vitro from the inner cell mass and polar trophoblast cells closely paralleled in vivo. The functional nature of various embryonic cell types observed in these embryos was revealed by scanning electron microscopy. These studies as well as those of Wiley and Pedersen (1977) suggest that blastocysts can serve as a source of in vitro developing early mouse egg cylinders that appear to resemble their in vivo counterparts and can be used in experimental studies of mouse embryogenesis.

Animals↗
PubMed1979

Hemopoiesis of the cultured whole mouse embryo.

In vitro cultured murine embryos provide a valuable methodology for studying the ontogeny of hemopoiesis in mammalian embryos. Under improved conditions, 49% of mouse embryos cultured from the blastocyst stage reached the early somite stage. The development of the embryo was arrested at different stages by omitting human cord serum from the culture medium at specific times. These observations suggest the appearance and differentiation of the first hemopoietic cells in the mouse yolk sac to be independent of a normal embryo. In the yolk sac of all cultured mouse embryos, hemopoietic cell differentiated into a major cell type, erythroblasts, and minor cell types such as monocytes, macrophages, and granulocytic cells. A small number of hemopoietic cells remained undifferentiated.

Animals↗
PubMed1977

Development of trophoblast and placenta of the mouse. A reinvestigation with regard to the in vitro culture of mouse trophoblast and placenta.

At 5 days post conceptionem (p.c.) shortly after implantation, giant cell transformation starts at the abembryonic pole of the blastocyst, spreading over the mural trophoblast; 1 day later, the first ectoplacental giant cells appear at the base of the fast growing ectoplacental cone (derived from the polar trophoblast). Giant cell transformation expands over it periphery. Thus, by the 8th day p.c., the conceptus is separated from the maternal tissue by a continuous layer of giant cells, variable in thickness. Giant cells reach their greatest size by 10 days p.c. in the mural tophoblast and by 12 days p.c. in the chorioallantoic placenta. They are probably no longer formed after that stage. Around the 8th day p.c., the allantois reaches contact with the ectoplacental cone, which develops into the chorioallantoic (definitive) placenta. At 9 days p.c., its four zones can already be discriminated: chorionic plate, labyrinth, junctional zone (trophospongium), and zone of giant cells, respectively. Within the next day, the chorioallantoic placental circulation is established. The yolk sac placental circulation is established by the 9th day p.c. The villi of the proximal layer of the yolk sac increase in size and number, and their capillary network becomes more dense until the 12th to 14th day p.c. This provides evidence that the yolk sac placenta exerts its function--to a certain extent--beyond the establishment of the definitive placenta. Around the 14th day p.c., the placental labyrinth reaches its definitive features. Fetal capillaries in the labyrinth, branching from unbilical blood vessels within the septa of connective tissue are surrounded by trophoblast cells. They form a dense vascular network bathing in maternal blood. The structures of the placental zones remain almost the same during further development, the borders becoming sometimes little blurred. Adjacent to the chorionic plate, subchorionic clefts appear at the 14th day p.c. These clefts become confluent to form the intraplacental space, regularly communicating with the yolk sac cavity. At the end of gestation (19th day p.c.) there is a considerable amount of eosinophilic material ('fibrinoid') between the zone of giant cells and the decidua, probably produced by the giant cells.

Animals↗
PubMed1975

Penetration of Trichophyton terrestre in human hair.

The systematic human hair degradation by Trichophyton terrestre was examined by electron and light microscopy. The cuticular and hair shaft regions were readily decomposed by the wild type or parent strain selected for phenotype studies after exposure to spaceflight parameters.

Hair↗