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Biomedical subjects

D E Keith

Publications and source records attributed to D E Keith.

25 records · Page 2Linked to original sources
PubMed1987

Antibodies to human immunodeficiency virus in human sera induce cell-mediated lysis of human immunodeficiency virus-infected cells.

The capacity of human immunodeficiency virus (HIV) antibody-positive sera from homosexually active men without acquired immune deficiency syndrome to lyse the HIV-infected T cell lines MOLT-4f and CCRF-CEM (CEM) in cooperation with lymphocytes from normal donors was investigated. Twenty-seven HIV antibody-positive sera, most of which enhanced the killing of HIV-infected MOLT-4f and CEM target cells by normal mononuclear cells were studied in detail. HIV antibody-positive sera resulted in lysis at dilutions as high as 1/10,000. HIV antibody-negative sera did not augment lysis of infected target cells. In addition, lysis of uninfected targets was not enhanced in the presence of HIV antibody-positive sera. Because fractionation of the HIV antibody-positive sera on a protein A affinity column resulted in recovery of the activity from the IgG fraction, the extra cytotoxic activity mediated by nonimmune cells in the presence of immune sera appears to be antibody-dependent. Furthermore, the cytotoxic effector cells were in the nonrosetting fraction of lymphocytes and expressed Leu-11 (cluster designation (CD)15) antigens, which is characteristic of cells participating in antibody-dependent cellular cytotoxicity reactions. The antibody specificity of the sera, determined by radioimmunoprecipitation, provides evidence that antibody-dependent cellular cytotoxicity can occur even when there are no detectable antibodies directed against gag proteins. Sera which lacked detectable antibodies to the envelope protein gp120 by radioimmunoprecipitation did not mediate antibody-dependent cellular cytotoxicity.

Adult↗
PubMed1986

Studies of the human c-myb gene and its product in human acute leukemias.

The myb gene is the transforming oncogene of the avian myeloblastosis virus (AMV); its normal cellular homolog, c-myb, is conserved across a broad span of evolution. In humans, c-myb is expressed in malignant hematopoietic cell lines and in primary hematopoietic tumors. Partial complementary DNA clones were generated from blast cells of patients with acute myelogenous leukemia. The sequences of the clones were compared to the c-myb of other species, as well as the v-myb of AMV. In addition, the carboxyl terminal region of human c-myb was placed in an expression vector to obtain protein for the generation of antiserum, which was used to identify the human c-myb gene product. Like v-myb, this protein was found within the nucleus of leukemic cells where it was associated with the nuclear matrix. These studies provide further evidence that c-myb might be involved in human leukemia.

Aspartate Carbamoyltransferase↗
PubMed1986

Identification and characterization of the protein encoded by the human N-myc oncogene.

The human N-myc gene is related to the c-myc proto-oncogene, and has been shown to have transforming potential in vitro. Many studies have reported amplification of N-myc in human neuroblastoma and retinoblastoma cell lines. In primary tumors, amplification of the gene was found to correlate directly with behavior of the tumor. Specific restriction fragments of a partial complementary DNA clone of N-myc from LA-N-5 human neuroblastoma cells were placed into a bacterial expression vector for the purpose of producing antigens representative of the N-myc protein. Rabbits immunized with these antigens produced antisera that recognized a protein of 62-64 kilodaltons in neuroblastoma cells. By several criteria, this protein appears to be part of the same proto-oncogene family as the c-myc protein. Moreover, the antisera to fragments of this protein were capable of histochemically identifying malignant cells in clinical specimens.

Animals↗
PubMed1982

Lysine tRNAs from Bacillus subtilis 168: structural analysis.

The primary sequence was established for two lysine tRNA isoacceptors which differ in abundance during development in Bacillus subtilis. Both tRNAs shared the same primary sequence but differed in the degree of post-transcriptional modification in the anticodon loop. The earlier eluting species, tRNA lys 1, had an unmodified C in position 32 and a mixture of N-[9-beta-ribofuranosyl) purin-6-ylcarbamoyl]-L-threonine, t6A, and N-[(9-beta-D-ribofuranosyl-2-methylthio-purin-6-yl)carbamoyl]threonine, ms2t6A, in position 37. The later eluting species, tRNA Lys 3, which is the more efficient in protein synthesis, had a modified C in position 32 and only ms2t6A in position 37. The possibility exists that modification to make a more efficient tRNA species may be part of a functional interaction between the translational and transcriptional changes that are part of the differentiation process in B. subtilis.

Anticodon↗
PubMed1982

Urine levels of N-[9-(beta-D-ribofuranosyl)purin-6-ylcarbamoyl]-L-threonine, N6-(delta 2-isopentenyl)adenosine, and 2'-O-methylguanosine as determined by radioimmunoassay for normal subjects and cancer patients.

Radioimmunoassays (RIA) are presented for the evaluation of the levels of the following three modified nucleosides in human urine: 2'-O-methylguanosine (Gm), N6-(delta 2-isopentenyl)adenosine (i6A), and N-[9-(beta-D-ribofuranosyl)purin-6-ylcarbamoyl]-L-threonine (t6A). Competitive inhibition of the RIA was provided by 2 to 10 microliters of untreated urine and the sensitivity of each RIA was in the pmol range. Partial fractionation of urine indicated that the majority of inhibitory activity was in the fraction coeluting with a nucleoside standard. The amounts of nucleosides in 24-hr urine samples from eight normal subjects were 2.2 +/- 0.9 mg (S.D.) for t6A; 0.17 +/- 0.09 mg for Gm; and 0.050 +/- 0.019 mg for i6A. The levels of t6A, i6A, and Gm were also determined by RIA of urine samples of patients with lymphomas or solid tumors. Levels of t6A were significantly elevated for patients with lung cancer (p less than 0.001), non-Hodgkin's lymphoma (p less than 0.05), and other solid tumors (p less than 0.02) but not for patients with Hodgkin's disease. The RIA data on the other two nucleosides, i6A and Gm, showed no similarly significant variations. Increased levels of t6A in the cancerous state were substantiated by isolating the t6A fraction from the urine of normal subjects of patients with lung cancer and quantitating the amount by use of UV adsorption. These preliminary results indicate that RIA for t6A might be clinically useful by providing a complementary approach to the assessment of the levels of modified nucleosides by gas-liquid or high-performance-liquid chromatography.

Adenosine↗
PubMed1981

Thiolation and 2-methylthio- modification of Bacillus subtilis transfer ribonucleic acids.

Six thionucleosides found in Bacillus subtilis transfer ribonucleic acids were investigated: N6-(delta 2-isopentenyl)-2-methylthioadenosine, 5-carboxymethylaminomethyl-2-thiouridine, 4-thiouridine, 2-methylthioadenosine, N-[(9-beta-D-ribofuranosyl-2-methylthiopurin-6-yl)carbamoyl]threonine, and one unknown (X1). The presence of N-[(9-beta-D-ribofuranosyl-2-methylthiopurin-6-yl)carbamoyl]threonine was demonstrated based on the affinity of the transfer ribonucleic acid containing it for an immunoadsorbent made with the antibody directed toward N-[9-(beta-D-ribofuranosyl)purin-6-ylcarbamoyl]-L-threonine. The existance of N-[(9-beta-D-ribofuranosyl-2-methylthiopurin-6-yl)carbamoyl]threonine in two species of lysine transfer ribonucleic acids was also confirmed by high-resolution mass spectrometry. Four of these thionucleosides--N6-(delta 2-isopenenyl)-2-methylthioadenosine, 2-methylthioadenosine, 5-carboxymethylaminomethyl-2-thiouridine, and the unknown designated X1--occurred only in specific areas in the elution profile of an RPC-5 column and probably affect the chromatographic properties of the transfer ribonucleic acids containing them. In contrast with Escherichia coli, where 4-thiouridine is the most frequent type of sulfur-containing modification, approximately one-third of the sulfur groups in B. subtilis transfer ribonucleic acid are present as thiomethyl groups on the 2 position of an adenosine or modified adenosine residue.

Adenosine↗