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At least 73 records · Page 4Linked to original sources
PubMed1984

The preservation of the ability of cultured quail wing bud mesoderm to elicit a position-related differentiative response.

A previous study showed that grafting wedges of fresh anterior quail wing mesoderm into posterior slits of chick wing buds resulted in the formation of rods and nodules of cartilage in a high percentage of cases (B. Carlson, 1983, Dev. Biol. 101, 97-105). The purpose of the present study was to determine if a similar response could be elicited by grafting pieces of mesoderm that had been cultured in vitro. When pieces of 1-day cultured anterior mesoderm from stage 17-24 donors were grafted into standard posterior slits of chick wing buds, the percentages of supernumerary structures differed little from those which formed after the grafting of pieces of fresh mesoderm. In a time series, grafts of stage 22-23 anterior mesoderm which had been cultured for 1-4 days retained the ability to form cartilage after being grafted into posterior locations. A time series showed that the duration of this retention was longer in cultured mesoderm than it was in mesoderm that remains in the donor wing bud.

Age Factors↗
PubMed1988

Collagens support embryo attachment and outgrowth in vitro: effects of the Arg-Gly-Asp sequence.

Collagen types I through VI support attachment and outgrowth of mouse blastocysts in vitro. We found that embryos acquire the ability to attach to collagens type II and VI relatively early in their developmental program. The time at which half of the embryos displayed outgrowth formation and the morphology of outgrowths formed on these two collagen types are similar to those observed for laminin, fibronectin, and hyaluronate. Embryos acquire the ability to outgrow on the other collagen types at a later time in culture. Both "native" and denatured collagens support embryo attachment and outgrowth, indicating that this activity is intrinsic to the primary collagens' structure. A synthetic peptide containing the sequence Arg-Gly-Asp inhibits embryo outgrowth on collagen type II and denatured collagen type IV, whereas a peptide containing the related sequence, Arg-Gly-Glu, has relatively little effect on embryo outgrowth. In contrast, embryo attachment to collagen types I, V, and VI was not inhibited specifically by the Arg-Gly-Asp peptide sequence. Consequently, it appears that embryos use multiple adhesion systems to attach to collagens. Among these are adhesion systems that have a peptide recognition specificity similar to that of fibronectin receptors. These studies indicate that embryo interactions with collagens may be one aspect of the tissue invasion processes that take place during implantation.

Amino Acid Sequence↗
PubMed1991

Gap junctional communication during limb cartilage differentiation.

The onset of cartilage differentiation in the developing limb bud is characterized by a transient cellular condensation process in which prechondrogenic mesenchymal cells become closely apposed to one another prior to initiating cartilage matrix deposition. During this condensation process intimate cell-cell interactions occur which are necessary to trigger chondrogenic differentiation. In the present study, we demonstrate that extensive cell-cell communication via gap junctions as assayed by the intercellular transfer of lucifer yellow dye occurs during condensation and the onset of overt chondrogenesis in high density micromass cultures prepared from the homogeneous population of chondrogenic precursor cells comprising the distal subridge region of stage 25 embryonic chick wing buds. Furthermore, in heterogeneous micromass cultures prepared from the mesodermal cells of whole stage 23/24 limb buds, extensive gap junctional communication is limited to differentiating cartilage cells, while the nonchondrogenic cells of the cultures that are differentiating into the connective tissue lineage exhibit little or no intercellular communication via gap junctions. These results provide a strong incentive for considering and further investigating the possible involvement of cell-cell communication via gap junctions in the regulation of limb cartilage differentiation.

Animals↗
PubMed1979

Gap junctional communication in the post-implantation mouse embryo.

We studied the extent of cell-to-cell communication via junctional channels in in vitro-implanted mouse blastocysts by monitoring ionic coupling and the spread of two injected low molecular weight dyes, fluorescein and Lucifer yellow. In the early attached embryos, both trophoblasts and cells of the inner cell mass (ICM) were ionically coupled to one another. Dye injections in either trophoblasts or ICM cells resulted in spread to the entire embryo. As older and more developed embryos were examined, the spread of injected dye was progressively more limited. In the most developed embryos examined, dye injected into a cell in the ICM region resulted in spread throughout the ICM but not into the surrounding trophoblast cells, while dye injected into a trophoblast cell did not spread to any other cell in the embryo. Simultaneous monitoring of ionic coupling and dye injections in embryos of intermediate stages in this transition revealed that the trophoblast and ICM cells were ionically coupled, even across the apparent boundary where no dye was observed to pass. In the latest stage embryos examined in which no injected dye was observed to move out of the ICM, ionic coupling was still observed between the cells of the ICM and the trophoblasts. Furthermore, in the more developed embryos, dye injected into the ICM region frequently was not transferred to all the cells of the ICM, thus suggesting a further compartmentalization of due spread within the ICM. Our observations that ionic coupling is more extensive than the detectable spread of injected dyes may perhaps reflect a reduced number of junctional channels. With fewer channels less dye would pass between cells, so that, together with continuous quenching, the transfer of injected dye would not be detectable. This partial segregation of cell-to-cell communication as indicated by the limited dye spread may parallel specific differentiation processes, in particular that of giant trophoblast, embryonic ectoderm and extraembryonic endoderm differentiation.

Animals↗
PubMed1979

Karyologically identified homozygous tw18 embryos: extrauterine growth properties and transformation by SV40.

A method for identifying individual embryos from crosses segregating homozygous t lethals using the marker chromosome Rb7 is described and applied to the tw18 haplotype. In contrast to wild-type and heterozygous littermates, homozygous tw18/tw18 6 and 8 day embryos have very limited growth potentialities in vitro. When transplanted under the testis capsule, homozygous tw18 embryos (3, 6 and 7 day) produce teratomas at a much lower efficiency than heterozygous and wild-type embryos, and the rare teratomas thus obtained have limited growth potentialities when cultured in vitro. Upon transformation with SV40, however, permanent lines of cells of mesodermal origin, capable of myoblastic or adipocytic differentiation, have been obtained. This shows that the effect of the mutation on cell growth can be overcome by SV40 transformation.

Animals↗
PubMed1986

Development of the ectoderm in Xenopus: tissue specification and the role of cell association and division.

When do ectodermal cells become specified to form epidermis, that is, become committed to form epidermis when isolated? Animal pole explants of Xenopus cultured in saline from the 8-cell stage onwards express a specific epidermal antigen, whereas vegetal explants do not. The isolated outer layer of ectoderm formed by stage 7 is almost completely specified, the inner layer is only partially so. When are cell associations and cell divisions necessary for epidermal differentiation? Embryos that were either disaggregated or incubated in cytochalasin B after the midblastula stage do not require cell interactions, Ca2+, or cell divisions for epidermal differentiation to occur. Inhibition of mRNA transcription with actinomycin D shows that the epidermal antigen is certainly transcribed by the late gastrula stage (stage 12).

Animals↗
PubMed1999

Pregnancy following transfer of ooplasm from cryopreserved-thawed donor oocytes into recipient oocytes.

OBJECTIVE: To determine if frozen-thawed donor oocytes could be used to provide cytoplasm for transfer into patients' oocytes to improve subsequent embryonic development. DESIGN: Prospective evaluation of the procedure in consenting IVF patients. SETTING: Assisted reproductive technology program. PATIENT(S): The study was open to consenting IVF patients (of any age) with a history of poor embryo quality or those couples in which the wife's age was > or = 40 years. INTERVENTION(S): Transfer of donor egg cytoplasm from frozen-thawed oocytes into the oocytes of infertile recipients. MAIN OUTCOME MEASURE(S): Donor oocyte survival following cryopreservation, fertilization following cytoplasmic transfer into recipient oocytes, embryo quality, and pregnancy outcome. RESULT(S): Oocytes collected from four donors were cryopreserved and 61% (28/46) survived the thaw procedure. Cytoplasmic transfer was performed on the eggs of four patients, with fertilization occurring in 70.3% (26/37). Twin pregnancy was established in one patient (35 years of age) with a history of poor embryo quality. CONCLUSION(S): Cryopreserved donor oocytes may provide a source of cytoplasm for transfer into recipient oocytes, eliminating the need for cycle synchronization between donor and infertile patient.

Adult↗