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J H Sinclair

Publications and source records attributed to J H Sinclair.

54 records · Page 3Linked to original sources
PubMed1982

Mapping the mitochondrial DNA of Zea mays: Ribosomal gene localization.

We have located the 18S and 26S ribosomal genes on a 32.2-kilobase pair (kb) restriction map of Zea mays mitochondrial DNA. In a BamHI restriction digest of mitochondrial DNA, band 4 carries all of the 26S gene whereas band 2 carries the 18S gene sequence. We have cloned and mapped bands 2 and 4 and show that they are contiguous in the genome. The 26S sequence is at one end of the 13.7-kb fragment 4, immediately adjacent to the junction with fragment 2. The 18S sequence is located at the far end of the 17.5-kb fragment 2, about 15 kb away from the 26S gene. A second region of 18S sequence homology is found on band 40. This region contains sequences that cross-hybridize with those in band 2. The nature of this apparent sequence repetition is unclear.

Journal Article↗
PubMed1978

Amphibian cells in culture. I. Nutritional studies.

Nutritional requirements of amphibian cells in culture were studied for the purpose of modifying a minimal medium in which frog cells could proliferate and which could be used for obtaining drug-resistant and auxotrophic variants. The serum, purine, CO2, and amino acid requirements for ICR 2A (a Rana pipiens haploid cell strain) have been investigated employing two different media: L-15, a nonbicarbonate, amino acid-buffered medium and Eagle's MEM, a bicarbonate-buffered medium. In this paper we present evidence to support the following conclusions: (1) With L-15 as the base medium, 10% fetal calf serum (FCS) supports optimal cell growth during exponential phase. Calf serum, whole, dialyzed, or heat-inactivated, cannot substitute for FCS and, in fact, is inhibitory. (2) Purines are required by ICR 2A cells only if grown in a nonbicarbonate-buffered medium, since the cells under these conditions cannot produce enough endogenous CO2 to support de novo purine synthesis. (3) In addition to the amino acids considered essential for mammalian cells in culture, ICR 2A cells depend upon exogenous asparagine. Glutamine and/or aspartic acid cannot replace the asparagine requirement. However, ICR 2A cells do utilized exogenous glutamine as an oxidative substrate.

Amino Acids↗
PubMed1978

Amphibian cells in culture. II. Isolation of drug-resistant variants and an asparagine-independent variant.

With L-15 as the base medium, drug-resistant variants were isolated from two amphibian tissue culture strains: the Xenopus laevis A8 diploid cell line and the ICR 2A cell line of Rana pipiens. Four different classes of variants were obtained: (1) A8 cells resistant to chloramphenicol, an inhibitor of mitochondrial protein synthesis; (2) A8 cells resistant to ouabain, an inhibitor of the Na+/K+-activated ATPase of the plasma membrane;(3) ICR 2A cells resistant to low (20 microgram/ml) and high (300 microgram/ml) levels of bromodeoxyuridine (BUdR), a thymidine analog which interferes with the pyrimidine salvage pathway; and (4) ICR 2A cells resistant to 2,6-diaminopurine (DAP), an adenine analog which interferes with the purine salvage pathway. Unlike the other variants, isolation of BUdR resistant cells is a 2-step process. Resistance to low levels of BUdR is phenotypically expressed by a reduction in thymidine transport activities while resistance to high levels of this compound is evidenced by greatly reduced levels of thymidine kinase activity. DAP-resistant cells, which are characterized by reduced levels of adenine phosphoribosyl transferase (APRT) activity, do not die in AAT (adenine, aminopterin, thymidine) selection medium. This suggests that these cells utilize adenine efficiently. With MEM as the base medium, an asparagine independent clone was isolated from the ICR 2A cell line. When compared with the wild type, this variant exhibited a slightly reduced growth rate in the presence or absence of asparagine.

Animals↗
PubMed1967

Mitochondrial-satellite and circular DNA filaments in yeast.

Mitochondrial DNA of Saccharomyces cerevisiae contains a satellite DNA (density, 1.682) that appears to exist as open-ended filaments at least 5 microns long. DNA from intact cells contains circular filaments whose lengths vary from 0.5 to 7 microns, with a great majority at 1.95 microns. The circular DNA has a density similar to that of the major nuclear peak (1.697). When heat-denatured mitochondrial-satellite DNA is renatured, it cross-links to form a molecule that is larger than the native molecule. The formation of cross-links results in hypersharpening of the density profiles in cesium chloride and also leads to failure to pass Millipore filter paper.

Centrifugation, Density Gradient↗