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At least 1,063 records · Page 59Linked to original sources
PubMed1979

Changes in the nuclear polyamine content of chick erythrocytes during embryonic development.

The polyamine content of the circulating erythrocyte population in the embryonic chick was studied during its development. Total cellular polyamine content fell dramatically between 5 and 7 days of development, paralleling the decrease in metabolic activity exhibited by these cells. Nuclei were isolated from the erythrocytes by a non-aqueous technique, which not only eliminated the polyamine loss that occurred with aqueous isolation, but also prevented redistribution of the polyamines from the cytoplasm. Nuclear spermidine and spermine contents decreased markedly between 5 and 6 days of development from 31 to 10 pmol/microgram of DNA and from 33 to 18 pmol/microgram of DNA respectively. Thereafter the spermine content remained constant, but the spermidine content continued to decline. Good correlations between spermidine and RNA contents were observed in both cells and nuclei, and similarly between spermine and RNA contents in cells, but no such correlation was observed between spermine and RNA in nuclei.

Age Factors↗
PubMed2004

Differential expression of 11beta-hydroxysteroid dehydrogenase types 1 and 2 mRNA and glucocorticoid receptor protein during mouse embryonic development.

Accumulating evidence suggests that the actions of glucocorticoids in target tissues are critically determined by the expression of not only the glucocorticoid receptor (GR) but also the glucocorticoid-metabolizing enzymes, known as 11beta-hydroxysteroid dehydrogenase types 1 and 2 (11beta-HSD1 and 11beta-HSD2). To gain insight into the role of glucocorticoids in fetal development, the expression patterns of the two distinct 11beta-HSD isozymes and GR were studied in the mouse embryo from embryonic day 12.5 (E12.5, term = E19) to postnatal day 0.5 (P0.5) by in situ hybridization and immunohistochemistry, respectively. 11beta-HSD1 mRNA was detected in the heart as early as E12.5 and maintained thereafter. In the lung and liver, 11beta-HSD1 mRNA was first detected between E14.5 and E16.5, increased to high levels towards term and maintained after birth. Relatively low levels of 11beta-HSD1 mRNA were also detected in the kidney, adrenal glands and gastrointestinal tract at E18.5. However, the mRNA for 11beta-HSD1 was undetectable in all other embryonic tissues including the brain. In contrast, kidney was the only organ that expressed appreciable levels of 11beta-HSD2 mRNA during embryonic life. The level of 11beta-HSD2 mRNA in the kidney increased dramatically in the newborn, which coincided with expression of 11beta-HSD2 mRNA in the whisker follicle, tooth and salivary gland. Distinct from the profiles of 11beta-HSD1 and 11beta-HSD2 mRNA, GR protein was detectable in all tissues at all ages studied except for the thymus, salivary gland, and bone. Taken together, the present study demonstrates that tissue- and developmentally-stage specific expression of 11beta-HSD1 and 11beta-HSD2 as well as GR occurs in the developing mouse embryo, thus highlighting the importance of these two enzymes and GR in regulating glucocorticoid-mediated maturational events in specific tissues during murine embryonic development.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed1993

Many spinal cord cells transiently express low molecular weight forms of glutamic acid decarboxylase during embryonic development.

At early developmental stages in the rat spinal cord (embryonic day 13), when neuronal progenitors are still proliferating, most differentiating neurons express truncated forms of glutamic acid decarboxylase (GAD) (approximately 25 kDa) which are the products of alternative splicing of the GAD67 gene. These truncated proteins do not appear to synthesize gamma-aminobutyric acid (GABA). The amino acid is detected in cells only after alternative splicing of the GAD67 gene generates a full-length, 67 kDa enzymatically active form of GAD. Both the 67 kDa GAD and GABA colocalize and appear diffusely distributed in the cytoplasm of embryonic neurons. GABA does not appear associated with synaptic vesicles until after birth, when its intracellular distribution becomes punctate and it colocalizes with synaptophysin. At this time, it also colocalizes with an immunologically distinct 65 kDa GAD protein encoded by a second GAD gene (GAD65). Expression of different GAD-related proteins with distinct intracellular distributions during development suggests that GABA, the product of these enzymes, may have trophic or metabolic roles during spinal cord differentiation.

Animals↗
PubMed1987

Early stages of embryonic development in two rabbit genotypes.

The origin of the early embryonic loss that occurs during the first 4 days after mating in Californian doe-rabbits has been studied at 24 h or 60 h post coitum (p.c.). For comparison, 11 New Zealand doe-rabbits were slaughtered at the same times. The development stage of the embryo was determined after examination in toto at 24 h or by counting the morula nuclei at 60 h on histological sections. At 24 h p.c., 5.3% of the New Zealand eggs had not divided vs 37% of the Californian ones; this difference was highly significant. At 60 h p.c. frequency histograms of the number of morula nuclei showed that development was more variable in Californian does than in the New Zealand ones. However, the mean number of morula nuclei of each genotype was not significantly different. The higher proportion of Californian eggs (compared to New Zealand eggs) that were unfertilized or showed retarded segmentation is the main cause of the unexpectedly lower prolificacy of Californian rabbits.

Animals↗
PubMed2007

Geminin in embryonic development: coordinating transcription and the cell cycle during differentiation.

Geminin was initially characterized as a bifunctional protein with roles in regulating the fidelity of DNA replication and in controlling cell fate during embryonic nervous system formation. More recently, Geminin's roles have expanded, encompassing regulation of cell proliferation and differentiation during retinogenesis, control of Hox transcription factor function during vertebrate axial patterning, and regulation of the timing of neuronal differentiation. Geminin interacts with homeodomain-containing transcription factors and with protein complexes that regulate chromatin structure, including Polycomb complexes and the catalytic subunits of the SWI/SNF chromatin remodeling complex, Brg1 and Brahma. Activities for Geminin in coordinating cellular events at the transition from proliferation to differentiation have recently emerged in multiple developmental contexts. This review will summarize Geminin's increasingly diverse roles as a developmental regulatory molecule.

Amino Acid Sequence↗
PubMed1991

Developmental regulation of gap junction gene expression during mouse embryonic development.

The expression of products from three different gap junction genes (alpha 1, beta 1 and beta 2) was studied in pre- and postimplantation mouse embryos, during organogenesis, during differentiation of F9 teratocarcinoma cells, and in cultured embryonic stem (ES) cells. In this analysis, the following results were obtained. 1) Pre- and postimplantation mouse embryos. The alpha 1 transcript was the earliest gap junction RNA detected (in the 4 cell stage embryo) and its abundance increased significantly throughout subsequent development. 2) Organogenesis. Evidence was obtained for developmental expression of these three different gap junction genes during early embryogenesis and throughout the late stages of organogenesis. The expression patterns for these genes may be related to differences in gap junctional communication requirements for fetal organ development versus neonatal and adult organ function, or the utilization of different genes by different cell types during organogenesis. 3) During the differentiation of F9 cells in culture, expression of these three genes was modulated. Thus, this is the first evidence for modulation of gap junction gene expression during the differentiation of a single cell type in culture. 4) In an ES cell culture line, alpha 1 was the only gap junction gene product detected. This is consistent with the findings of alpha 1 expression in the embryonic inner cell mass region and in undifferentiated teratocarcinoma cells.

Amino Acid Sequence↗