Search PubMed⌕ Search

Biomedical subjects

M Rabinowitz

Publications and source records attributed to M Rabinowitz.

At least 127 records · Page 7Linked to original sources
PubMed1975

Sequence homology of the mitochondrial leucyl-tRNA cistron in different organisms.

Sequence divergence of the mitochondrial leucytl-tRNA cistron in several eukaryotes has been examined by RNA-DNA hybridized. Rat mitochondria Leucyl-tRNA was hybridized with rat, mouse, guinea pig, monkey, chicken, and yeast mitochondrial DNAs (mtDNA) immobilized onfilters. Hybridization was carried out in 50% formamide (Tm -12degrees) or in 20% fromamide (Tm -21degrees). melting profiles of the hybrids were obtained for evaluation of the extent of base sequence micmatching. Under the more stringent hybridization conditions (50% formamide, Tm -12degrees), only mouse and quines pig mtDNAs hybridized with rat mitochondrial leucyl-tRNA. The Tm's of the heterohybrids were depressed by 2 and 9 degrees, respectively. Under less stringent hybridization conditions (Tm-21 degrees), monkey mtDNA also hybridized, and the Tm was depressed by about 15 degrees. Chicken and yeast mtDNAs did not form specific hybrids with rat mibochondrial leucyl-tRNA under these hybridization conditions. Mitochondrial leucyl-tRNA sequences in different eukaryotes appear to be conserved to a less extent than cytoplasmic rRNA, 5S RNA, or hemoglobin mRNA sequences.

Animals↗
PubMed1975

Sequence homology between mitochondrial DNAs of different eukaryotes.

The sequence divergence of mitochondrial DNAs (mtDNA) from rat, mouse, guinea pig, monkey, and chicken has been examined by DNA-DNA hybridization. mtDNAs, isolated as closed circular molecules by propidium iodide-CsCl centrifugation, were labeled in vitro by use of Escherichia coli DNA polymerase I, and renatured (Tm-35 degrees) in the presence of a 2500-fold excess of heterologous mtDNA. Single-stranded and duples DNA were separated by hydroxylapatite chromatography. The thermal stability of heteroduplexes was compared to the homoduplex by thermal elution chromatography on hydroxylapatite columns. Heteroduplex fromation between the tritiated myDNAs and a 2500-fole excess of rar mtDNA were 70, 59, 37, and 22%, respectively, for mouse, guinea pig, monkey, and chicken. Similar results were obrained in reciprocal hybridizations where one of the other mtDNAs was present in excess. Considerable mismatching of sequences in all the heterohybrids was indicated by a 18-24 degrees depression in the te50 of the heteroduplexes compared with the homoduplex. There was no apparent change in heteroduplex formation when the concentration ratio of driving DNA in excess to [3H]mtDNA was varied between 1250 and 7500. Furthermore, a second renaturation with excess driving DNA after completion of the first reaction resulted in no detectable augmenting of heteroduplex formation. Similar sequences appear to be conserved preferentially in different organisms, since the presence of two of fouf different heterologous mtDNAs in excess resulted in only moderate and nonadditive increases in heteroduplex formation. Evolutionary divergence of mtDNA sequences appears to have occurred at rates similar to that for unique sequences nuclear DNA.

Animals↗
PubMed1975

Restriction endonuclease analysis of mitochondrial DNA from grande and genetically characterized cytoplasmic petite clones of Saccharomyces cerevisiae.

Digestion of grande mitochondrial DNA (mtDNA) BY EcoRI restriction endonuclease gives rise to nine fragments with a total molecular weight of 51.8 x 10(6). HindIII digestion yields six fragments with a similar total molecular weight. Specific restriction fragments can be detected despite the fact that yeast mtDNA consists of a heterogeneous distribution of randomly broken molecules. Digestion patterns of 10 genetically characterized petite clones containing various combinations of five antiobiotic resistance markers indicate that the petite mtDNA predominantly represents deletion of the grande genome. The petite mtDNAs contained up to seven EcoRI restriction fragments which comigrate with grande restriction fragments, and at least one fragment that did not correspond to any in the grande. Some strains contained multiple fragments with mobility different from that of grande; these fragments were usually present in less than molar concentrations. The genetic markers were associated with individual sets of restriction fragments. However, several internal inconsistencies prevent the construction of a definitive genetic fragment map. These anomalies, together with the digestion patterns, provide strong evidence that, in addition to single contiguous deletion, other changes such as multiple deletion and heterogeneity of mtDNA populations are present in some of the petite mtDNAs.

DNA Restriction Enzymes↗
PubMed1975

Translation of RNA that contains polyadenylate from yeast mitochondria in an Escherichia coli ribosomal system.

RNA that contains poly(A) [poly(A)-RNA] has been isolated from yeast mitochondria by poly(U) Sepharose-4B column chromatography. Pulse-labeled poly(A)-RNA shows 8-10 discrete peaks by acrylamide gel electrophoresis. The specific activity of mitochondrial poly(A)-RAN is six to eight times greater than that of mitochondrial rRNA after pulse labeling of protoplasts with [3H-]uridine. Ethidium bromide inhibits incorporation by over 90%. The total mitochondrial RNA preparation was contaminated with 5-15% cytoplasmic rRNA as determined by gel electrophoresis, but RNA exhaustion hybridization experiments indicated little or no cytoplasmic contamination of the mitochondrial poly(A)-RNA. The poly(A)-RNA stimulates [3H]leucine incorporation into protein in an E. coli cell-free system. A fraction of the labeled product is precipitated with antibody directed toward yeast cytochrome oxidase, but not with antibody directed toward bovine serum albumin. Sodium dodecyl sulfate gel electrophoresis of the immunoprecipitated material reveals labeled peptides having the mobility of the three larger cytochrome oxidase peptides, which are known to be translated by mitochondrial ribosomes.

Cell-Free System↗
PubMed1974

Tandem inverted repeats in mitochondrial DNA of petite mutants of Saccharomyces cerevisiae.

Denatured mitochondrial DNA (mtDNA) from a grande (wild-type) yeast strain and a series of derived genetically characterized cytoplasmic petite mutants was examined in the electron microscope as DNA-protein monolayers prepared under conditions that permitted little bimolecular renaturation. In the grande and some petite strains, the mtDNA remained predominantly single-stranded. However, in several petite strains, a large proportion of molecules contained double-stranded segments indicative of unimolecular renaturation due to the presence of inverted repeat sequences. The length of the double-stranded segments of strain E41 was compared to the periodicity seen on denaturation maps. A repeat spacing twice the length of the inverted repeats was observed in the denaturation map. Inverted repeat length was similar to contour length of circular mtDNA molecules in this strain. On the basis of these observations most of the mtDNA from petite strain E41 appeared to consist of polymers of tandem inverted repeats interspersed with a small single-stranded "spacer" sequence between the repeat segments. In contrast, petite strain F13 mtDNA had few or no inverted repeats and showed a regular periodicity of 0.14 mum in the denaturation map, similar in length to the 0.13-mum circles present in the isolated mtDNA.

Base Sequence↗
PubMed1974

Studies of human lead metabolism by use of stable isotope tracers.

Dynamics of lead metabolism were studied by replacement of a portion of the dietary lead with stable isotope tracers, and maintaining subjects on controlled diets for about 6 months. Results for one subject have been previously reported. Preliminary data are now available for a second subject. Although the data on the two subjects are basically similar, there are also significant differences. The two subjects have different blood lead concentrations (0.25 and 0.18 mug/g). Both subjects received the same dietary and similar atmospheric lead exposure, and the lead concentration of their blood was shown to be nearly in a steady state. The difference in blood lead concentration appears primarily attributable to differences in the fraction of lead absorbed from the gut, although there are also differences in other physiological parameters, as well as probable small differences in their intake of atmospheric lead. The quantity of lead absorbed from a typical urban atmosphere (Pb concentration = 1-2 mug/m(3)) has been shown by our isotopic data and balance studies to be 15+/-3 mug/day. Measurement of the contribution of atmospheric lead to the lead intake of the second subject was also carried out by removal of lead from the atmosphere. Decline in the blood concentration of lead of normal isotopic composition was shown to be equivalent to the removal of 15 g/day. Measurements made during the course of a day show complexities in the absorption and distribution of lead, which are averaged out on a time scale of ca. 5 days.

Air Pollution↗
PubMed1974

Upwardly mobile.

Explore the source record for details and available documents.

Ethics, Dental↗