Negative correlation between the change in bone mineral density and serum osteocalcin in patients with hyperthyroidism

To assess the changes in bone mineral density and osteoblastic activity in patients with hyperthyroidism and to investigate the relationship between those changes, we measured bone mineral density and serum osteocalcin in 109 patients with Graves' disease, comprising 75 untreated patients and 34 patients under treatment, and 200 normal controls. The degree of change in bone mineral density was quantified with Z transformation, in which we used means and SDs of bone mineral densities obtained in the process of age- and sex-matched 1:1 pairing developed by ourselves. Bone mineral density was low in female patients with hyperthyroidism in the spine, femur neck, trochanter, and Ward's triangle, but was not low in male patients. Serum osteocalcin was elevated in patients with untreated Graves' disease and correlated negatively with the Z values of bone mineral densities of the spine, femur neck, and trochanter. In conclusion, indices of osteoblastic activity were elevated in patients with hyperthyroidism, probably secondary to a thyroid hormone-induced increase in bone resorption which resulted in reduced bone mineral density. Quantification of the change in bone mineral density by using the parameters derived in the process of age- and sex-matched pairing seems to be an efficient method for statistical analyses.

Whole-abdomen radiation therapy in ovarian carcinoma: its role as a salvage therapeutic modality

A significant proportion of patients with epithelial ovarian carcinoma eventually fail after initial responses to chemotherapy. Further treatment with chemotherapy consisting of either the same combination or second-line regimens has been ineffective in producing durable responses. Thus, between June 1983 and June 1987, thirty patients with epithelial ovarian carcinoma who failed one or more chemotherapeutic regimens were treated with whole-abdominopelvic-cavity radiation therapy. Prior to the radiation the amount of residual disease after debulking was noted to be microscopic in 16 patients and macroscopic in 14 patients. Radiation was delivered with an open-field technique that extended from the domes of the diaphragm to the obturator foramina. Doses of 2500 cGy were planned to the whole abdomen, with a boost of another 2500 cGy to the pelvic and or paraaortic nodes when indicated. Higher doses were delivered to the areas of gross disease in the pelvis. Only 2 patients were unable to complete the planned therapy. Another 26% of the patients required interruption of the therapy secondary to hematologic toxicity but eventually completed the treatment. With an overall median follow-up of 14 months, 56% of the patients remain alive. Two-year actuarial survival and recurrence-free survival rates are 47 and 32%, respectively. The survival and recurrence-free survival rates for the group with microscopic residual disease--61 and 33%, respectively--are better than those for the patients with macroscopic residual disease--36 and 18%. The abdominopelvic cavity was the first site of failure in all but one of the 17 patients who have failed. In spite of the higher doses, pelvic failure alone or as a component occurred in 54% of the patients. Small bowel obstruction necessitating surgical intervention as a complication of therapy was seen in 13% of the patients.

Mutagenesis by single site-specific arylamine-DNA adducts. Induction of mutations at multiple sites

Two related carcinogen adducts, N-(deoxyguanosin-8-yl)-2-aminofluorene (AF) or N-(deoxyguanosin-8-yl)-N-acetyl-2-aminofluorene (AAF), were introduced into the lacZ' gene at base position 6253 of the minus strand of M13mp9 viral DNA. The construction of this site-specifically modified DNA was accomplished by first preparing a gapped heteroduplex missing 7 nucleotides at position 6251-6257 followed by ligation with an unmodified heptamer or with a heptamer containing either an AF or AAF adduct. These site-specifically modified templates were transfected into competent wild-type Escherichia coli cells (JM103) and a uvrA strain (SMH12). The mutation spectrum was determined by phenotypic selection of colorless plaques indicating a defective beta-galactosidase marker enzyme and by an in situ hybridization procedure to detect single base pair mismatches in the adduct region. DNA sequencing was used to characterize 179 of the mutants obtained. We found that both adducts were capable of inducing base substitution mutations at the adduct site and in the local region of the adduct. A specific frameshift (+1G) was also observed at a displaced site. All of the frameshift mutations occurred at the ligation site of the modified oligonucleotide. Control experiments with an unmodified oligonucleotide did not show an enhancement of mutations at this site, indicating that the adducts may have been responsible for these frameshifts. The mutations spectra induced by these adducts suggest that mutagenesis depends not only on adduct structure but also the sequence in which the adduct is located and the host cell type used for mutation expression.

Inhibition by diacylmethane derivatives of mutagenicity and nucleic acid binding of 2-aminofluorene derivatives

The active methylene compounds acetylacetone, 1,1,1-trifluoroacetylacetone, benzoylacetone, dibenzoylmethane, and 1,3-indandione inhibited the mutagenicity of 2-nitrofluorene in Salmonella typhimurium. They also inhibited the N,O-acetyltransferase-catalyzed transfer RNA binding of N-hydroxy-2-acetylaminofluorene, but they did not inhibit N,O-acetyltransferase. However, only 1,3-indandione and 1,1,1-trifluoroacetylacetone significantly inhibited the binding of N-acetoxy-2-acetylaminofluorene to transfer RNA. Reaction of the trifluoro compound with the acetoxy compound yielded 1-(N-2-fluorenylacetamido)acetone. These results demonstrate that active methylene compounds can inhibit mutagenicity and nucleic acid binding of chemical carcinogens.

Basal-level expression of the yeast HSP82 gene requires a heat shock regulatory element

Previous studies have shown that heat shock factor is constitutively bound to heat shock elements in Saccharomyces cerevisiae. We demonstrate that mutation of the heat shock element closest to the TATA box of the yeast HSP82 promoter abolishes basal-level transcription without markedly affecting inducibility. The mutated heat shock element no longer bound putative heat shock factor, either in vitro or in vivo, but still resided within a nuclease-hypersensitive site in the chromatin. Thus, constitutive binding of heat shock factor to heat shock elements in S. cerevisiae appears to functionally direct basal-level transcription.

Subtalar joint coalition in children: new observations

Eleven children with clinical and radiographic findings suggestive of nonosseous subtalar coalition were found to have fibrous bridges at the time of surgery. A second group of 14 children with similar clinical and radiographic findings is being conservatively treated at present. This series of children suggests that a common site of nonosseous subtalar coalition is found posterior to the sustentaculum tali. Diagnosis of nonosseous coalition requires careful examination with computed tomography, with attention to subtle changes in the hindfoot, particularly posterior to the sustentaculum tali.

Complete assignment of the 1H NMR spectrum of a synthetic zinc finger from Xfin. Sequential resonance assignments and secondary structure

A 25-residue synthetic peptide corresponding to zinc finger 31 of the Xenopus protein Xfin adopts a compact, folded conformation in the presence of zinc. Complete 1H resonance assignments have been made. The peptide contains a helix, beginning as an alpha-helix and ending as a 3(10)-helix, that extends from residue 12 to 23. Several positively charged and polar residues located on this helix are likely to be involved in interactions with DNA. Residues 1-10 appear to adopt a hairpin-like structure.

The Escherichia coli primosome can translocate actively in either direction along a DNA strand

The primosome is a mobile multiprotein DNA replication-priming apparatus that requires seven Escherichia coli proteins (replication factor Y (protein n'), proteins n and n", and the products of the dnaB, dnaC, dnaT, and dnaG genes) for assembly at a specific site (termed a primosome assembly site) on single-stranded DNA binding protein-coated single-stranded DNA. Two of the protein components of the primosome have intrinsic DNA helicase activity. The DNA B protein acts in the 5'----3' direction, whereas factor Y acts in the 3'----5' direction. The primosome complex has DNA helicase activity when present at a replication fork in conjunction with the DNA polymerase III holoenzyme. In this report, evidence is presented that the multiprotein primosome per se can act as a DNA helicase in the absence of the DNA polymerase III holoenzyme. The primosome DNA helicase activity can be manifested in either direction along the DNA strand. The directionality of the primosome DNA helicase activity is modulated by the concentration and type of nucleoside triphosphate present in the reaction mixture. This DNA helicase activity requires all the preprimosomal proteins (the primosomal proteins minus the dnaG-encoded primase). Preprimosome complexes must assemble at a primosome assembly site in order to be loaded onto the single-stranded DNA and act subsequently as a DNA helicase. The 5'----3' primosome DNA helicase activity requires a 3' single-stranded tail on the fragment to be displaced, while the 3'----5' activity does not require a 5' single-stranded tail on the fragment to be displaced. Multienzyme preprimosomes moving in either direction are capable of associating with the primase to form complete primosomes that can synthesize RNA primers.

Three-dimensional solution structure of a single zinc finger DNA-binding domain

The three-dimensional solution structure of a zinc finger nucleic acid binding motif has been determined by nuclear magnetic resonance (NMR) spectroscopy. Spectra of a synthetic peptide corresponding to a single zinc finger from the Xenopus protein Xfin yielded distance and dihedral angle constraints that were used to generate structures from distance geometry and restrained molecular dynamics calculations. The zinc finger is an independently folded domain with a compact globular structure in which the zinc atom is bound by two cysteine and two histidine ligands. The polypeptide backbone fold consists of a well-defined helix, starting as alpha and ending as 3(10) helix, packed against two beta strands that are arranged in a hairpin structure. A high density of basic and polar amino acid side chains on the exposed face of the helix are probably involved in DNA binding.

A clinical study of hemorrhagic fever with renal syndrome caused by Seoul virus infection

The clinical findings of 29 patients with hemorrhagic fever with renal syndrome (HFRS) caused by Seoul virus were evaluated and compared with the previously reported clinical findings of classic Korean hemorrhagic fever (KHF). The diagnoses of these patients were made by hemagglutination inhibition test. The results were as follows: 1) The disease occurred predominantly in males with a high incidence in the third and fourth decades of life. 2) The highest incidence of the disease occurred in October-December. 3) Major symptoms were fever, abdominal or flank pain, vomiting and myalgia. 4) Major signs were petechia, CVA tenderness, pharyngeal injection, and conjunctival infection, but these signs were much less common than in patients with classic KHF. 5) The treatments were mainly conservative and there was no fatal case in the study subjects. These findings suggest that the clinical course of Seoul virus infection may be much milder than that of classic KHF and the outcome may be more favorable.

Detection of two alternative bcr/abl mRNA junctions and minimal residual disease in Philadelphia chromosome positive chronic myelogenous leukemia by polymerase chain reaction

The Philadelphia (Ph') chromosome in chronic myelogenous leukemia (CML) results in fusion of the bcr gene and c-abl oncogene, which transcribes into two types of chimeric bcr/abl mRNAs: the L-6 junction and the K-28 junction. By means of a highly sensitive assay, combination of reverse transcription and polymerase chain reaction (RT/PCR), we analyzed 38 blood samples obtained from 31 patients with Ph'-positive CML and two patients with Ph'-negative bcr rearranged CML. Among the 21 samples obtained in chronic phase, eight patients had the L-6 mRNA, 11 had the K-28 mRNA, and two had both the L-6 and K-28 mRNAs. Among the nine samples obtained in blast crisis, four contained the L-6 mRNA, two contained the K-28 mRNA, and three contained both the K-28 and L-6 mRNAs. This finding supports the concept of alternative splicing of bcr/abl mRNAs transcribed in Ph'-positive CML. However, it appears to be a rare event. Of the eight samples obtained from eight patients who had achieved complete cytogenetic remission and negativity for bcr region rearrangement for 6 months to 3 years after recombinant alpha interferon (r alpha-IFN) therapy, all of them showed evidence of minimal residual Ph'-positive clones as detected by the RT/PCR assay. This finding suggests that interferon therapy suppresses the proliferation of the Ph'-positive clones, but it does not completely eradicate the Ph'-positive stem cells.

Preoperative chemotherapy and irradiation for stage III non-small cell lung cancer

Surgical therapy for stage III non-small cell lung cancer (NSCLC) has not resulted in substantial long-term survival. Neoadjuvant treatment programs that could down-stage the tumor and achieve increased long-term survival would be of obvious benefit. We have used preoperative simultaneous chemotherapy and irradiation in 85 patients with clinical stage III non-small cell lung cancer considered candidates for surgical resection. One group of 56 patients was treated with cisplatin, 5-fluorouracil, and simultaneous irradiation for five days every other week for a total of four cycles. After treatment, 39 patients underwent resection, and the operative mortality was 2 (5%) of 39. A second trial was undertaken in which etoposide (VP-16) was added because of its synergism with cisplatin. In this group, 29 patients were considered to have potentially resectable disease, and 23 underwent thoracotomy with 1 operative death (4%). Of the total of 62 patients having thoracotomy, 60 underwent resection (97%). Complications were major, and there were four bronchopleural fistulas. For the 85 patients eligible for surgical intervention in these two groups of patients, the Kaplan-Meier median survival estimate is 40% at 3 years. The median survival of the 62 patients having thoracotomy is 36.6 months. Combination preoperative chemotherapy and irradiation is feasible with acceptable toxicity and operative mortality in patients with clinical stage III non-small cell lung cancer. Prospective randomized studies are suggested for further evaluation of this treatment program.

Metabolism of aromatic amines: relationships of N-acetylation, O-acetylation, N,O-acetyltransfer and deacetylation in human liver and urinary bladder

N-Acetoxyarylamines are reactive metabolites that are implicated in the initiation of the carcinogenic process by some N-substituted aryl compounds. The objective of this study was to explore the relationship between the production of these reactive species and N-acetylation (NAT), a reaction previously demonstrated to be polymorphic in the human. Human liver and urinary bladder mucosa samples were frozen within 4-8 h post mortem. These tissues were assayed for the (i) O-acetylation (OAT) of N-hydroxy-3,2'-dimethyl-4-aminobiphenyl (N-OH-DMABP) by acetyl CoA, (ii) intramolecular N,O-acetyltransfer (AHAT) of N-hydroxy-2-acetylaminofluorene (N-OH-AAF), (iii) NAT of 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA) by acetyl CoA and (iv) deacetylation of N-OH-AAF. Cytosolic AHAT and OAT showed partial inhibition by paraoxon. The ratio of paraoxon insensitive AHAT to OAT to NAT of PABA to NAT of 2-AF appears to be 1:2:11:22 using freshly made cytosols from frozen livers. Freezing of the cytosol resulted in extensive loss of activities. All four of these cytosolic enzyme activities exhibited a similar polymorphic response. Microsomal deacetylation showed a monomorphic response. Similar to the liver, urinary bladder epithelial cells also catalyzed the same reactions. However, the OAT and AHAT activities were detected mainly in microsomes. These data suggest that phenotypically rapid acetylators have a greater biochemical potential for the metabolic activation of aromatic amines by pathways that involve O-acetylation.

A perfusion system developed for 31P NMR study of melanoma cells at tissue-like density

A perfusion culture system has been developed for 31P NMR study of human uveal melanoma metabolism by adapting the Vitafiber I cartridge system (Amicon). 31P NMR spectra collected weekly during periods of up to 10 weeks demonstrated increasing levels of phosphorus metabolites as the anchorage-dependent cells grew to tissue-like density.

Ras oncogene mutations are rare late stage events in chronic myelogenous leukemia

DNA from bone marrow and peripheral blood samples of 44 chronic myelogenous leukemia (CML) patients were analyzed for the presence of mutations of codons 12, 13 or 61 of the N-ras, H-ras, or K-ras genes. In seven patients, samples were available from both their chronic phase and blast crisis. A total of 29 samples examined were at chronic phase and 22 were at blast crisis (eight lymphoid, eight myeloid, and six undifferentiated). No mutations were identified in N-ras or H-ras. Two patients in myeloid blast crisis had K-ras mutations, one patient at codon 12, the other at codon 13. In the former patient the mutation was not present and the latter patient was not tested in chronic phase. Our findings indicate ras mutations are an infrequent late stage event in CML that occur in myeloid blast crisis.

Serum cholesterol of residents in north Iowa

A survey of serum cholesterol levels was done on 219 residents in north Iowa. Population reference values of serum cholesterol for the community were developed. Data indicate age is an influential factor in both sex groups. Consumption of oral contraceptives appears to be a significant factor in increased serum cholesterol levels in females. Although cigarette smoking seems to augment serum cholesterol level superficially, its relationship is not statistically significant in the study.

Recognition and elongation of telomeres by telomerase

Telomeres stabilize chromosomal ends and allow their complete replication in vivo. In diverse eukaryotes, the essential telomeric DNA sequence consists of variable numbers of tandem repeats of simple, G + C rich sequences, with a strong strand bias of G residues on the strand oriented 5' to 3' toward the chromosomal terminus. This strand forms a protruding 3' over-hang at the chromosomal terminus in three different eukaryotes analyzed. Analysis of yeast and protozoan telomeres showed that telomeres are dynamic structures in vivo, being acted on by shortening and lengthening activities. We previously identified and partially purified an enzymatic activity, telomere terminal transferase, or telomerase, from the ciliate Tetrahymena. Telomerase is a ribonucleoprotein enzyme with essential RNA and protein components. This activity adds repeats of the Tetrahymena telomeric sequence, TTGGGG, onto the 3' end of a single-stranded DNA primer consisting of a few repeats of the G-rich strand of known telomeric, and telomere-like, sequences. The shortest oligonucleotide active as a primer was the decamer G4T2G4. Structural analysis of synthetic DNA oligonucleotides that are active as primers showed that they all formed discrete intramolecular foldback structures at temperatures below 40 degrees C. Addition of TTGGGG repeats occurs one nucleotide at a time by de novo synthesis, which is not templated by the DNA primer. Up to 8000 nucleotides of G4T2 repeats were added to the primer in vitro. We discuss the implications of this finding for regulation of telomerase in vivo and a model for telomere elongation by telomerase.

Thalamic syndrome and cortical hypoperfusion on technetium-99m HM-PAO brain SPECT

The six patients included in this study had painful dysesthesia, resulting from vascular lesions in or near the thalamus, confirmed by computerized tomography(CT) brain scan. Using hexamethyl propyleneamine oxime(HM-PAO) single photon emission computed tomography(SPECT) brain scanning, regional cerebral perfusion(rCP) was demonstrated. In contrast to three patients with lesions near the thalamus who showed symmetrical cortical radioactivity, the other three patients with thalamic lesions revealed decreased rCP in the ipsilateral cerebral cortex on HM-PAO brain SPECT. We thought that the loss of afferent activating stimuli from the thalamus led to decreased cortical neuronal activity and the following hypoperfusion. In patients with thalamic syndrome resulting from thalamic lesions, the role of the remote effect of the thalamic damage and consequent cortical deregulation in the development of thalamic pain and/or neuropsychological symptoms cannot be excluded completely.

A case of recurrent infantile polycystic kidney associated with hydrops fetalis

Nonimmune hydrops fetalis is becoming a predominant form of fetal hydrops due to the declining incidence of immune hydrops fetalis triggered by Rh isoimmunization. Infantile polycystic kidney appeared to be related to hydrops fetalis whether it is causal or merely coincidental and may represent another entry to differential diagnoses. Infantile polycystic kidney was diagnosed by an elevated maternal serum alpha-fetoprotein (AFP) value coupled with an ultrasonographic abnormality scanned as a multicystic mass with ascites in the fetal abdomen antenatally. This study presents a case of infantile polycystic kidney that resulted in a stillborn baby with hydrops fetalis and extensive placental calcification; it was the first case in Korea in which nonimmune hydrops fetalis was associated with infantile polycystic kidney in consecutive siblings by autosomal recessive inheritance in one family. In addition, this paper comprehensively reviews the incidence, etiology, prenatal diagnosis and proper management of nonimmune hydrops fetalis.

Multiple symmetric lipomatosis

Multiple symmetric lipomatosis (MSL) is an extremely uncommon disorder. In the medical literatures about 200 cases have been reported. MSL is not associated with other generalized lipomatous disorders, nor are these patient to be necessarily obese. The cause of MSL is unknown. The disorder usually occurs in middle-aged males and there is frequently a history of alcoholism. Some instances of familial occurrence have been reported, but the majority of cases are sporadic. Two cases of MSL are presented.

N- and O-deacetylation of N-acetoxy-N-arylacetamides by mammalian hepatic microsomes

The present study demonstrates that hepatic microsomes from guinea pigs, rats, mice, hamsters, rabbits and dogs catalyze N-deacetylation of N-hydroxy-2-acetylaminofluorene (N-OH-AAF) and N-hydroxy-3,2'-dimethyl-4-acetylaminobiphenyl and O-deacetylation of N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) and N-acetoxy-3,2'-dimethyl-4-acetylaminobiphenyl (N-AcO-DMAABP). Gel filtration resolves the solubilized guinea pig microsomal enzymes into two deacetylases. The larger molecular weight enzyme catalyzes N-deacetylation of N-OH-AAF, whereas the smaller one cannot. Both enzymes catalyze O-deacetylation of N-AcO-AAF and N-AcO-DMAABP, but the activity is mainly due to the larger enzyme. Guinea pig and rat liver microsomes also catalyze N-deacetylation of N-AcO-AAF resulting in the binding of 2-aminofluorene to nucleic acids, but the activities are much less than that of the O-deacetylation of N-AcO-AAF. Thus, the amino-fluorene-DNA adducts which have been found in intact cells treated with N-AcO-AAF may result directly from N-deacetylation or indirectly from N,O-acetyltransfer following O-deacetylation.

Detection of minimal residual bcr/abl transcripts by a modified polymerase chain reaction

The Philadelphia (Ph1) chromosome in chronic myelogenous leukemia (CML) involves reciprocal translocation of the bcr gene and the c-abl oncogene. The fused bcr/abl gene is transcribed into two types of chimeric mRNA. By means of a combined method of S1 nuclease protection and polymerase chain reaction, we amplified sequences representative of the chimeric bcr/abl transcripts. Only 5 micrograms of total cellular RNA is needed and the chimeric bcr/abl message can be detected at a dilution of 1:100,000. We also detected residual chimeric bcr/abl transcripts in the remission samples from two Ph1-positive CML patients. This technique has the potential to identify a subpopulation of Ph1-positive CML patients in remission who are at high risk of relapse.

Induction of repair synthesis of DNA in mammary and urinary bladder epithelial cells by N-hydroxy derivatives of carcinogenic arylamines

Unscheduled DNA synthesis (UDS)-inducing activity was used as a parameter to estimate the abilities of rat mammary epithelial cells and urothelial cells from various species to activate carcinogenic aromatic amine derivatives. The N-hydroxy, N-hydroxy-N-acetyl, N-hydroxy-N-glucuronosyl derivatives of 2-aminofluorene (2-AF) and 4-aminobiphenyl (4-ABP) induced UDS in primary cultures of rat mammary epithelial cells, but 2-AF, the O-glucuronide of N-hydroxy-N-acetyl-2-AF (N-OH-AAF) and 4-ABP did not. Neither the activity of N-OH-AAF, N-hydroxy-N-formyl-2-AF, nor N-acetoxy-N-acetyl-2-AF was significantly altered by paraoxon, an inhibitor of microsomal N-deacetylase. Although N-hydroxy-3,2'-dimethyl-4-aminobiphenyl (N-OH-DMABP) also induced UDS, its N-acetyl derivative, which can not be activated by intramolecular, N,O-acetyltransfer, did not. Similarly, rat urothelial cells were responsive to the UDS-inducing activity of this hydroxylamine, but not the hydroxamic acid. In contrast, dog urothelial cells were responsive to both compounds. The UDS-inducing activity of N-OH-AAF was inhibited by paraoxon in the dog, but not in rat urothelial cells. N-Hydroxy-N,N'-diacetylbenzidine induced UDS in the urothelial cells of dog, rat, and rabbit, and a human urothelial cell line, HCV-29, whereas benzidine, N-acetylbenzidine, and N,N'-diacetylbenzidine did not. Co-treatment with 12-O-tetradecanoylphorbol-13-acetate did not enable benzidine to induce UDS in dog urothelial cells. Rat mammary epithelial cells activated N-OH-DMABP by acetyl coenzyme A-dependent O-acetylation and N-OH-AAF by N,O-acetyltransfer. They could not N-deacetylate N-OH-AAF. These results suggest that rat mammary and bladder epithelial cells are capable of activating N-arylhydroxylamine metabolites of these carcinogens, probably by N,O-acetyltransfer and O-acetylation, whereas dog urothelial cells are more likely to activate these metabolites by N-deacetylation and a reaction that has yet to be identified.

Comparison of mutagenesis induced in single- and double-stranded M13 viral DNA by treatment with N-hydroxy-2-aminofluorene

The specificity of mutagenesis in single-stranded and its complementary double-stranded DNA of the bacteriophage M13mp8 induced by N-hydroxy-2-aminofluorene (N-OH-AF) was analyzed after transfection into its bacterial host Escherichia coli, strain JM103. In this forward mutation assay, randomly modified DNA with increasing levels of aminofluorene (AF) guanine adducts was transfected into competent host JM103 cells with or without prior induction of SOS functions in the host cells. These cells were then screened for mutants of the marker enzyme, beta-galactosidase, on a selective medium. In this assay, the mutation frequency was increased up to 10-fold in host cells with induced SOS functions as compared to the control host cells. Transfection of AF-substituted single-stranded DNA gave a 2.5-fold higher mutation frequency as compared to the double-stranded form at similar levels of AF modification and plaque-forming efficiency. DNA sequence analysis of the mutants showed that AF-modified single- and double-stranded DNA induced base substitutions (52-55%), large deletions (i.e. greater than 300 bp, 25-30%) and frameshifts (16-18%). The mutation sites for 73 base substitutions and frameshifts examined within a limited DNA sequence of 120 bases (6280-6400) were different in single- and double-stranded DNAs. A possible 'hotspot' for base substitutions within one of the two GGCG sequences has also been identified in single-stranded but not double-stranded DNA.