Mode of mutagenic action of methylnitrosocyanamide, a potent carcinogen.

A potent carcinogen, methylnitrosocyanamide was used to induce revertants in a strain of Escherichia coli carrying an amber mutation in a gene for tryptophan (trp) biosynthesis and an ochre mutation in a gene for alkaline phosphatase biosynthesis. Trp+ revertants were purified and classified into seven categories based on their ability to support the growth of particular nonsense mutants of phage lambda and on their content of alkaline phosphatase. About 90% of the Trp+ revertants induced by methylnitrosocyanamide were due to mutations in suppressor genes, and 85% of the suppressor mutations occurred in gene supE. Intragenic reversion cannot occur by a GC leads to AT base substitution mutation, whereas this is the obligate mode of mutation in gene supE. We conclude that methylnitrosocyanamide preferentially induces GC leads to AT transition mutations but that other base substitution mutations are also induced at about 10% of this frequency. N-Methyl-N-nitrosourea and, particularly, N-methyl-N'-nitro-N-nitrosoguanidine also preferentially induce GC leads to AT transition mutations.

c-kit gene expression in CD7-positive acute lymphoblastic leukemia: close correlation with expression of myeloid-associated antigen CD13.

Expression of human c-kit proto-oncogene and interleukin-7 receptor (IL-7R) in acute lymphoblastic leukemia (ALL) cells expressing CD7 was examined by Northern-blot analysis and reversed transcription polymerase chain reaction (RT-PCR) assay in relation to the phenotypes. Leukemic cells from four out of 12 CD7+ ALL patients, all of which fulfilled the criteria of ALL in the FAB classification, expressed c-kit genes. Surface CD3 (sCD3) was absent in all of these cases, while cytoplasmic CD3 (cCD3) was found in the two sCD3- cases. CD3 epsilon transcripts were detected in one of the sCD3- cCD3- cases. IL-7R genes were transcribed in the three cases with c-kit gene expression. In addition, there was a good correlation between c-kit gene expression and myeloid associated antigen CD13 positivity of the leukemic cells. None of the patients with c-kit gene expression had mediastinal tumor. Our results show that leukemic cells in a proportion of CD7+ ALL express receptors for cytokines that are secreted by bone marrow stromal cells. Ligands for c-kit genes and IL-7 could play an important role for the regulation of proliferation and differentiation of T-cell progenitors in bone marrow.

Mode of mutagenic action of 4-benzoylamido- and 4-acetamido-4-carboxamido-n(N-nitroso)-butylcyanamide.

The mode of mutagenic action of 4-benzoylamido- and 4-acetamido- 4-carboxamido-n(N-nitroso)-butylcyanamide (BCNBC, ACNBC) was studied using Escherichia coli K12 strains. The strains carrying defects in DNA-repair mechanism, AB2463 (recA) and P3478 (polA) were more sensitive than their parent strains to both compounds, while AB1886 (uvrA) showed the same sensitivity as the parental strain. About 90% of tryptophan revertants from BE1043 (trpambphoamb) by both compounds were due to mutation in suppressor genes. Suppressor analysis by using BE1047 (trpambphooch) revealed that the most frequently occurring reversion was due to a mutation in suppressor gene, supE. This implies that these two alkylnitrosocyanamides predominantly induce GC leads to AT transition.

[Spontaneous transient remission in adult acute myeloid leukemia].

A spontaneous complete remission for one month duration was observed in a 54-year-old female with acute myeloid leukemia. She had no documentation of apparent infection and blood transfusions, although they were ordinarily associated with spontaneous remission.

[Transient large granular lymphocytosis associated with pulmonary tuberculosis: a case report].

We report a case of a 61-year-old woman with large granular lymphocytosis associated with pulmonary tuberculosis. She was admitted to our hospital because of high fever, anemia and splenomegaly. On admission, the leukocyte count was 6,890/microliters with 52% of large granular lymphocytes. Immunophenotypical analysis of the increased cells showed following results; CD2+, CD3-, CD16+, CD57+. These cells had natural killer (NK) activity. Molecular genetical analysis showed these cells had germline configuration of the T cell receptor beta chain genes. About four months after admission, chest X-P revealed multiple mass shadow and the diagnosis of pulmonary tuberculosis was made by the examination of gastric juice. Anti-tuberculosis therapy was started, and soon after clinical symptom and pancytopenia were improved. For about one year, anti-tuberculosis therapy was continued, and now hematological abnormality is not found. We considered that this case was reactive large granular lymphocytosis of NK cells to lung tuberculosis.

Properties of mitomycin C-sensitive mutants of Escherichia coli K-12.

Strains hypersensitive to mitomycin C (MC) were isolated from Escherichia coli K-12 after treatment with nitrosoguanidine. Of 43 MC-sensitive strains tested for their ultraviolet light (UV) sensitivity and for their ability to reactivate UV-inactivated lambda phage, 38 were found to be insensitive to UV irradiation and to be able to reactivate UV-irradiated bacteriophage lambda. Some properties of the MC-sensitive, uvr(+) mutants were analyzed. Synthesis of deoxyribonucleic acid (DNA) in MC-sensitive, uvr(+) mutants was inhibited at a lower concentration of MC than in the wild-type strain. Mutant cells, labeled with (3)H-thymidine and then exposed to MC, released radioactivity as low molecular weight compounds. The amount of radioactivity released was the same as that from the wild-type strain. MC-sensitive, uvr(+) mutants, as well as the corresponding wild-type strain, were equally susceptible to induction of prophage phi80 by UV irradiation. However, MC induction of prophage was achieved in MC-sensitive, uvr(+) mutants at a lower concentration of the antibiotic than in the wild-type strain. Genetic experiments indicated that a gene controlling MC sensitivity is located close to that determining lactose fermentation of E. coli. It is situated on episome F'13, and the wild type is dominant to the MC-sensitive allele.

Effect of mutation to streptomycin resistance on amber suppressor genes.

Three classes of nonidentical streptomycin-resistant mutations were distinguished in Escherichia coli by their effect on the efficiency of suppression by an amber suppressor gene, sup E. The first class of mutation caused a strong restriction in efficiency of suppression of an amber codon in various cistrons of phage lambda and in an alkaline phosphatase structural gene of E. coli. The second class caused weak restriction, and the third class caused no restriction. The restrictive effect of the streptomycin resistance mutation of the first class on the sup E gene was reduced by addition of streptomycin. This mutation had little effect on efficiencies of suppression by amber suppressor genes sup D and sup F. Analyses on the alkaline phosphatase formed in the suppressor strain indicated that mutation to restrictive streptomycin resistance causes a reduction in translation of the amber codon in the alkaline phosphatase structural gene.

Location of the Escherichia coli K-12 ruv gene affecting septum formation after inhibition of deoxyribonucleic acid synthesis.

Escherichia coli ruv gene was located at 36.1 min on the chromosome by P1 transduction experiments and the gene order his - supD - uvrC, dar4 - ruv - eda - fadD - pps was proposed. Complementation analysis by an F' factor carrying genes in the his region indicated that ultraviolet light sensitivity genes, ruv and uvrC, consist of different cistrons and wild-type alleles of these genes are dominant over the mutant alleles.

Ultraviolet light sensitivity of Escherichia coli K-12 strains carrying ruv mutations in combination with uvrA or lon mutant alleles.

Strains of Escherichia coli K12 have been prepared that carry the ruv mutation in combination with lon or uvrA mutant alleles. The ruv minus uvrA minus double mutant is more sensitive to ultraviolet light than the urvA minus single mutant, whereas the strain with ruv and ion mutations shows the same sensitivity to ultraviolet light as the ruv minus single mutant.