Deoxyribonucleic acid strandedness. Partial characterization of the antigenic regions binding antibodies in lupus erythematosus serum.

This study shows that tritiated thymidine labeled DNA prepared from mammalian cells by the Marmur technique is a pure preparation of nucleic acid that is composed essentially of two populations of molecules. One molecular population consists of primarily double-standed nucleic acid, while the other population is of double-stranded nucleic acid with significant single-stranded regions. The double-stranded DNA with single-stranded regions can, depending upon the length of the single strand, behave as "native" DNA or "denatured" DNA on methylated albumin kieselguhr (MAK) column chromatography, Using MAK chromatography we have separated the DNA into a saltelutable fraction composed of primarily double-stranded molecules and an alkaline-elutable fraction containing double-stranded nucleic acid with variable length, single-stranded regions. Endonuclease enzyme removal of the single-stranded regions from the alkaline fraction DNA yield nucleic acid that behaves identically to the salt elutable DNA. Exonuclease removal of the single-stranded regions suggests they are located primarily at the ends of the molecules. Our data show that the alkaline-elutable DNA differs from salt-elutable DNA only in that the former has significant single-stranded regions. Sera of patients with systemic lupus erythematosus (SLE) selected for anti-DNA by hemagglutination bind significantly less to the alkaline fraction DNA than the sale fraction DNA. This difference in binding clearly does not represent simply an affinity for double-stranded vs. single-stranded nucleic acid since the alkaline fraction DNA contains predominately double-stranded nucleic acid. A model for antibody-DNA binding is suggested from the present data and information contained in the literature.

Arsenic intoxication as a cause of megaloblastic anemia.

We have described a case of chronic arsenic intoxication associated with pancytopenia and megaloblastic erythropoiesis. The patient had the typical laboratory manifestations of effective erythorpoiesis due to a megaloblastic process, including macroovalocytes, mild pancytopenia, low reticulocyte index, increased marrow cellularity with erythroid hyperplasia, and morphologic evidence of megaloblastic maturation in the marrow. The patient's serum folate and vitamin B12 were normal, and the anemia regressed without therapy. Our case suggests that the combination of megaloblastosis with normoblastic or megaloblastic karyorrhexis,should raise the suspicion of arsenic intoxication in the mind of the observer. In addition, arsenic should be added to the list of agents causing a reversible megaloblastic anemia.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. V. Isolation of additional hybrids which differ in their simian virus 40-specific biological properties.

Four new nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses have been isolated. Although these viruses (designated Ad2(+)ND(2), Ad2(+)ND(3), Ad2(+)ND(4), and Ad2(+)ND(5)) were clonal derivatives of the same Ad2-SV40 hybrid population, they differ significantly from each other and from the previously isolated nondefective hybrid, Ad2(+)ND(1), in their biological properties or in the amount of SV40-specific RNA induced during lytic infection.Like Ad2(+)ND(1), Ad2(+)ND(2), and Ad2(+)ND(4) pass serially in both human embryonic kidney (HEK) and primary African green monkey kidney cells. In contrast, Ad2(+)ND(3) and Ad2(+)ND(5) pass serially only in HEK cells. Ad2(+)ND(2) is like Ad2(+)ND(1) in that it induces the SV40 U antigen, but not SV40 T antigen; however, in contrast to the perinuclear SV40 antigen induced by Ad2(+)ND(1), the SV40 antigen induced by Ad2(+)ND(2) is located peripherally in the cytoplasm as well as in the perinuclear region of infected cells. Ad2(+)ND(4) induces both the SV40 T and U antigens. Ad2(+)ND(3) and Ad2(+)ND(5) do not induce serologically detectable SV40 antigens and are distinguished from each other on the basis of the relative quantities of SV40-specific RNA which they induce. The induction of different SV40-specific functions suggests the incorporation of different segments of SV40 DNA within the genomes of the respective hybrid viruses.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. VI. Characterization of the DNA from five nondefective hybrid viruses.

Certain biophysical characteristics of the DNA from each of the five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses (Ad2(+)ND(1), Ad2(+)ND(2), Ad2(+)ND(3), Ad2(+)ND(4), Ad2(+)ND(5)) have been determined. The guanine plus cytosine content varied from 55 to 57% and was not significantly different from that of nonhybrid Ad2 (56%), and the hybrid DNA molecules had mean molecular lengths which were similar to that of the standard, Ad2. The Ad2 and SV40 components of each hybrid were linked by alkali-resistant, presumably covalent bonds. The percentage of SV40 DNA in each hybrid virus was determined by hybridization with SV40 complementary RNA in a calibrated system. The results indicate that each hybrid virus DNA contains a different percentage of SV40 nucleotide sequences. The estimated size of the SV40 DNA component varies from 48,000 daltons for Ad2(+)ND(3) to 840,000 daltons for Ad2(+)ND(4), the latter being equivalent to between one-fourth and one-third of the SV40 genome.