Megan L Norris

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It has been suggested that the failure of parthenogenetic mouse embryos to develop to term is primarily due to their aberrant cytoplasm and homozygosity leading to the expression of recessive lethal genes. The reported birth of homozygous gynogenetic (male pronucleus removed from egg after fertilization) mice and of animals following transplantation of(More)
It has been assumed that most, if not all, signals regulating early development have been identified. Contrary to this expectation, we identified 28 candidate signaling proteins expressed during zebrafish embryogenesis, including Toddler, a short, conserved, and secreted peptide. Both absence and overproduction of Toddler reduce the movement of(More)
Expression and DNA methylation of the transgene locus TKZ751 are controlled by genotype-specific modifier genes. The DBA/2 and 129 genetic backgrounds enhanced expression, while the BALB/c background suppressed expression, but only following maternal inheritance of the BALB/c modifier. Epigenetic modification of the transgene locus was cumulative over(More)
There has been much speculation on whether mammalian eggs with two male pronuclei can develop normally. Eggs with two female pronuclei can sometimes develop as far as the 25-somite stage but with only very meagre extraembryonic tissues. We suggested that the genome undergoes specific imprinting during gametogenesis and that some paternal genes may be(More)
Deficits on two continuous performance test versions and the forced-choice span of apprehension task, which are potential vulnerability factors for schizophrenic disorders, were examined in relationship to particular symptoms of schizophrenic disorders, with emphasis on hypothesized relationships to formal thought disorder and negative symptoms. These(More)
Transgenic mice carrying the human cytomegalovirus immediate early gene promoter driving the E. coli lacZ gene displayed an unusual cell specific expression of beta-galactosidase during development. LacZ expression was first detected in cells lining the apex of the neural fold of day 8.5 embryos. By day 10 of gestation, expression was prominent in the(More)
A systematic analysis of parthenogenetic (PG) cell fate within the central nervous system (CNS) was made throughout fetal development and neonatal and adult life. Chimeras were made between PG embryos carrying a ubiquitously expressed lacZ transgene and normal fertilized embryos. After detailed histological analysis, we find that the developmental potential(More)
A detailed analysis of the developmental potential of parthenogenetic embryonic stem cells (PGES) was made in vivo and in vitro, and a comparison was made with the development of cells from parthenogenetic embryos (PG). In vivo, in chimeras with normal host cells (N), PGES cells showed a restricted tissue distribution consistent with that of PG cells,(More)
Exploratory factor analysis (EFA) is a widely used but poorly understood statistical procedure. This paper described EFA and its methodological variations. Then, key methodological variations were used to evaluate EFA usage over a 10-year period in five leading developmental disabilities journals. Sixty-six studies were located and evaluated on multiple(More)
The fate of parthenogenetic cells was investigated during development of fetal and early postnatal chimeras. On day 13 of embryonic development, considerable contribution of parthenogenetic cells was observed in all tissues of chimeric embryos, although selection against parthenogenetic cells seemed to start before day 13. Between days 13 and 15 of(More)