PubMed Health⌕ Search

Biomedical subjects

R F Baker

Publications and source records attributed to R F Baker.

At least 37 records · Page 2Linked to original sources
PubMed1978

Evidence for translocation of DNA sequences during sea urchin embryogenesis.

Hairpin-like DNA was prepared in vitro from the family of sequences that are inverted relative to each other and, as pairs, are relatively homologous and adjacent on the sea urchin genome. The majority of these hairpins are shown to have base pair mismatch positions distributed along their stems. Comparison of the hairpins derived from the DNA of morula, blastula, and gastrula stage embryos shows that during embryogenesis there are changes in the average number and position of S1 nuclease-sensitive base pair mismatch sites on the majority of the hairpin stems. Our data indicate that during early embryogenesis there are sequence changes in vivo within the majority of the adjacent inverted repeat sequences of the sea urchin genome. We have also found that there is higher specificity for the occurrence of sequence-change events within that fraction of the inverted repeat sequences that are methylated in vivo.

Animals↗
PubMed1975

The effect of 5-bromodeoxyuridine on the synthesis of nuclear and cytoplasmic DNA-binding proteins isolated from sea urchin embryos.

Newly synthesized DNA-binding proteins were isolated from the nuclei and, separately from, the cytoplasm of sea urchin mofula stage embryos. The presence of 5-bromodeoxyuridine during embryogenesis did not appear to alter the synthesis of either class of DNA-binding proteins. This result tends to argue that cell differentiation in early embryos is not regulated by differential synthesis of DNA-binding proteins. Sea urchin mofulae synthesize a broad range, by molecular weight, or cytoplasmic DNA-binding proteins which dissociate from sea urchin DNA-cellulose at relatively high salt concentrations (0.6-2.0 M NaCl). The most prominant of these apparently high-binding-affinity proteins has an approximate molecular weight of 33,000.

Animals↗
PubMed1974

Single-stranded regions in DNA isolated from different developmental stages of the sea urchin.

Long-term labeled sea urchin embryo (Strongylocentrotus purpuratus) DNAs were examined for size of recovered pieces, single-strandedness, and length of continuous double-stranded regions. Sizing on neutral sucrose gradients indicates that morula stage DNA sediments predominantly at 31 S, blastula stage DNA at 27 S, and gastrula stage DNA as a broad range of sizes of greater than 29 S. Treatment of [3H]thymidine-labeled DNA with Aspergillus oryzae S1 nuclease removes 19% of the 3H from morula stage DNA, 4% of the 3H from blastula stage DNA, and less than 0.1% of the 3H from gastrula stage DNA. Sedimentation of S1 nuclease treated [3H]DNAs on alkaline sucrose gradients indicates that in native morula stage DNA there is a nick or gap in one strand approximately every 9700 base pairs, in native blastula stage DNA about every 3300 base pairs, and very few nicks or gaps in native gastrula stage DNA.

Animals↗
PubMed1972

Selective inhibition of genetic transcription in sea urchin embryos. Incorporation of 5-bromodeoxyuridine into low molecular weight nuclear DNA.

Experimental evidence suggests that exposure of sea urchin gastrulae to 5-bromodeoxyuridine (BUdR), an analog of thymidine, causes a reduction in the rate of synthesis of some RNA species usually transcribed at this stage of development. In pulse-chase experiments, (3)H (in gastrula stage 8-15S nuclear DNA labeled with BUdR-(3)H) could not be chased, with unlabeled BUdR, into 20-60S size-range DNA; in similar experiments in which gastrulae were pulsed with thymidine-(3)H and then chased with unlabeled thymidine, (3)H in 8-15S nuclear DNA could be extensively chased into 20-60S DNA. DNA-RNA hybridization assays indicate that gastrula stage nuclear DNA in the range of 20-60S has greater sequence homology for gastrula stage RNA-(3)H than does nuclear DNA of similar size-range taken from gastrulae exposed to BUdR for 1 hr. An explanation is offered for the effect of BUdR on transcription and DNA replication in sea urchin embryos.

Animals↗
PubMed1972

Disruption of chemically killed bacterial cells by a synthetic zeolite.

The applicability of a synthetic zeolite (type 4A, Union Carbide Corp., Linde Div., New York, N.Y.) as a disruptive agent in a procedure for the preparation of pure bacterial cell wall fractions from a variety of phenol-killed gram-negative, gram-positive, and acid-fast bacteria was demonstrated. The disruptive effect was found to be limited with formaldehyde-killed gram-positive cells and most gram-positive cocci killed either by phenol or formaldehyde.

Bacteria↗