Infecciones parasitarias intestinales y factores asociados a la infección por coccidias en pacientes adultos de un hospital público de Lima, Perú / Parasite intestinal infection and factors associated with coccidian infection in adults at public hospital in Lima, Peru

Objective: To evalúate the frequency of intestinal parasites and risk factors associated with coccidian infection in patients cared for at a public hospital in Lima-Peru. Methods: A descriptive, cross-sectional study was conducted using reports of the parasitology laboratory. Patients included were >18 years, who gave at least one faecal sample for parasitologic evaluation. Logistic regression was used to calcúlate Odd Ratios (OR) and 95 percent) confidence intervals. Results: 2.056 patients were included in the analysis, 55.2 percent> of them were males and 334 (16.3 percent) were HlVpositive. Overall, Blostocystis hominis was the most frequent parasite (35.4 percent). The multivariate model adjusted for sex shows that HIV infection (OR = 4.53; 95 percentCI: 3.03-6.77), being hospitalized (OR = 2.42; 95 percentCI: 1.06-5.52), and age ≥ 40 years (OR = 0.57; 95 percentIC: 0.37-0.86) were associated with coccidian mfection. Conclusions: Blostocystis hominis was the most frequent parasite in HIV positive and negative patients. Being hospitalized and HIV infection were risk factors for coccidian infection, but age ≥ 40 years was a protective factor.

Objetivos: Evaluar la frecuencia de parásitos intestinales y factores asociados a la infección por coccidias en un hospital público de Lima-Perú. Métodos: Estudio descriptivo, transversal, realizado con los reportes del Laboratorio de Parasitología. Se incluyeron pacientes de > 18 años, ambulatorios u hospitalizados, que tuvieron al menos una muestra de heces evaluada. Usando regresión logística, se calcularon OR e IC al 95 por ciento. Resultados: Se incluyó 2.056 pacientes en el análisis; 55,2 por ciento fueron varones y 334 (16,3 por ciento) fueron seropositivos para VIH. La infección parasitaria más frecuente fue Blastocystis hominis (35,4 por ciento). El modelo multivariado ajustado por sexo mostró que la infección por VIH (OR = 4,53), estar hospitalizado (OR = 2,42) y la edad ≥ 40 (OR = 0,57) estuvieron asociados con infección por coccidias. Conclusiones: Blastocystis hominis se aisló frecuentemente en pacientes con y sin infección por VIH. Estar hospitalizado y ser seropositvo para VIH fueron factores de riesgo para infección por coccidias, mientras la edad ≥ 40 años fue un factor protector.

Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro.

In palisade mesophyll cells of spinach (Spinacia oleracea L.) kept under low-intensity white light, chloroplasts were apparently immobile and seemed to be surrounded by fine bundles of actin filaments. High-intensity blue light induced actin-dependent chloroplast movement concomitant with the appearance of a couple of long, straight bundles of actin filaments in each cell, whereas high-intensity red light was essentially ineffective in inducing these responses. The actin organization observed under low-intensity white light has been postulated to function in anchoring chloroplasts at proper intracellular positions through direct interaction with the chloroplasts. Intact chloroplasts, which retained their outer envelopes, were isolated after homogenization of leaves and Percoll centrifugation. No endogenous actin was detected by immunoblotting in the final intact-chloroplast fraction prepared from the leaves kept under low-intensity white light or in darkness. In cosedimentation assays with exogenously added skeletal muscle filamentous actin, however, actin was detected in the intact-chloroplast fraction precipitated after low-speed centrifugation. The association of actin with chloroplasts was apparently dependent on incubation time and chloroplast density. After partial disruption of the outer envelope of isolated chloroplasts by treatment with trypsin, actin was no longer coprecipitated. The results suggest that chloroplasts in spinach leaves can directly interact with actin, and that this interaction may be involved in the regulation of intracellular positioning of chloroplasts.

Structure and function of plant canopies.

This section comprises a set of papers taken from those presented at a symposium held to commemorate the 50th anniversary of the Monsi-Saeki theory (1953), together with invited papers. The papers describe recent advances in the study of structure and function of plant canopies and are written by former students (and their collaborators) of Professors Monsi and Saeki. The topics cover construction and maintenance of efficient photosynthetic systems at leaf, individual plant and stand level. Canopy structure and function are analysed with respect to optimization and an evolutionarily stable strategy. A new translation of the original paper by Monsi and Saeki (1953) into English has been commissioned and is included in this section.

The effect of internal CO2 conductance on leaf carbon isotope ratio.

We estimated internal CO2 conductance (gi) for C3 plant species of different life forms (annual herbs, deciduous trees and evergreen trees) grown in a variety of environments to examine the effect of gi on their leaf carbon isotope ratio (delta13C). The purpose of this study was to test the validity of using delta13C as an index of photosynthetic water use efficiency (WUE). When comparing deciduous tree species grown in contrasting light environments, there was a strong positive relationship between delta13C and WUE. Similarly, delta13C was positively correlated to WUE when comparing the different species of evergreen trees. However, the difference in WUE between evergreen and deciduous tree species did not relate to that in leaf delta13C. In addition, WUE was similar between highland and lowland herbaceous plants, although the former had a much higher delta13C. The positive relationship between delta13C and WUE did not hold across different life forms and different altitudes when differences in gi did not relate to those in stomatal conductance, resulting in independence of chloroplast CO2 partial pressure from intercellular CO2 partial pressure.

[Human blastocystosis: prospective study symptomatology and associated epidemiological factors]. / Blastocystosis humana: estudio prospectivo, sintomatologia y factores epidemiologicos asociados.

An attempt has been made to contribute to the understanding of the symptoms and factors associated with the Blastocystis Hominis infection, as seen in persons seeking outside consultation from the Dermatological and Transmissible Diseases Department (DTDD) at the C.H.N.H. This is a case-control study carried out in people between the ages of 5 and 80 in a period from January to March 1999. The cases tested positive in parasitological tests for Blastocystis Hominis and were absent of other enteropathogens. The controls tested negative in parasitological tests for Blastocystis Hominis and were absent of other enteropatoghens. A clinical chart was used to register details of symptomatology and factors associated with the Blastocystis Hominis infection. 74 cases and 70 controls were studied, matched by sex and age. A statistical correlation was obtained (p<0.05) among symptomatic persons and presence of Blastocystis Hominis (91,9%). The symptomatology associated with the Blastocystis Hominis infection by order of statistical significance (p<0.05) was: Abdominal pain (OR=3) 1.47

Mechanism of lower genotoxicity of toremifene compared with tamoxifen.

An increased incidence of endometrial cancer has been reported in breast cancer patients taking tamoxifen (TAM) and in healthy women participating in the TAM chemoprevention trials. Because TAM-DNA adducts are mutagenic and detected in the endometrium of women treated with TAM, TAM adducts are suspected to initiate the development of endometrial cancer. Treatment with TAM has been known to promote hepatocarcinoma in rats, but toremifene (TOR), a chlorinated TAM analogue, did not. TAM adducts are primarily formed via sulfonation of the alpha-hydroxylated TAM metabolites. To explore the mechanism of the lower genotoxicity of TOR, the formation of DNA adducts induced by TOR metabolites was measured using (32)P-postlabeling/ high-performance liquid chromatography analysis and compared with that of TAM metabolites. When alpha-hydroxytoremifene was incubated with DNA, 3'-phosphoadenosine 5'-phosphosulfate, and either rat or human hydroxysteroid sulfotransferase, the formation of DNA adducts was two orders of magnitude lower than that of alpha-hydroxytamoxifen. alpha-hydroxytoremifene was a poor substrate for rat and human hydroxysteroid sulfotransferases. In addition, the reactivity of alpha-acetoxytoremifene, a model activated form of TOR, with DNA was much lower than that of alpha-acetoxytamoxifen. Thus, TOR is likely to have lower genotoxicity than TAM. TOR may be a safer alternative by avoiding the development of endometrial cancer.

Miscoding potential of the N2-ethyl-2'-deoxyguanosine DNA adduct by the exonuclease-free Klenow fragment of Escherichia coli DNA polymerase I.

Acetaldehyde, a major metabolite of ethanol, reacts with dG residues in DNA, resulting in the formation of the N(2)-ethyl-2'-deoxyguanosine (N(2)-Et-dG) adduct. This adduct has been detected in lymphocyte DNA of alcohol abusers. To explore the miscoding property of the N(2)-Et-dG DNA adduct, phosphoramidite chemical synthesis was used to prepare site-specifically modified oligodeoxynucleotides containing a single N(2)-Et-dG. These N(2)-Et-dG-modified oligodeoxynucleotides were used as templates for primer extension reactions catalyzed by the 3' --> 5' exonuclease-free (exo(-)) Klenow fragment of Escherichia coli DNA polymerase I. The primer extension was retarded one base prior to the N(2)-Et-dG lesion and opposite the lesion; however, when the enzyme was incubated for a longer time or with increased amounts of this enzyme, full extension occurred. Quantitative analysis of the fully extended products showed the preferential incorporation of dGMP and dCMP opposite the N(2)-Et-dG lesion, accompanied by a small amounts of dAMP and dTMP incorporation and one- and two-base deletions. Steady-state kinetic studies were also performed to determine the frequency of nucleotide insertion opposite the N(2)-Et-dG lesion and chain extension from the 3' terminus from the dN.N(2)-Et-dG (N is C, A, G, or T) pairs. These results indicate that the N(2)-Et-dG DNA adduct may generate G --> C transversions in living cells. Such a mutational spectrum has not been detected with other methylated dG adducts, including 8-methyl-2'-deoxyguanosine, O(6)-methyl-2'-deoxyguanosine, and N(2)-methyl-2'-deoxyguanosine. In addition, N(2)-ethyl-2'-deoxyguanosine triphosphate (N(2)-Et-dGTP) was efficiently incorporated opposite a template dC during DNA synthesis catalyzed by the exo(-) Klenow fragment. The utilization of N(2)-Et-dGTP was also determined by steady-state kinetic studies. N(2)-Et-dG DNA adducts are also formed by the incorporation of N(2)-Et-dGTP into DNA and may cause mutations, leading to the development of alcohol- and acetaldehyde-induced human cancers.

Effects of virus infection and light environment on population dynamics of Eupatorium makinoi (Asteraceae).

We studied the effects of virus infection on dynamics of three Eupatorium makinoi populations in contrasting light environments, Gora-dani (a shaded population) and Minou 1 and Minou 2 (open-site populations). Censuses of the plants were taken for 8 yr in Gora-dani and 4 yr in Minou 1 and Minou 2. After the epidemics of virus infection, most plants were virus infected at both sites. The number of plants and the proportion of flowering individuals decreased rapidly and simultaneously in the shaded population in Gora-dani. By contrast, in the open-site populations of Minou, the proportion of flowering plants decreased first, and then the number of plants decreased gradually. Growth analysis of the plants in the Gora-dani population revealed that stem growth was significantly suppressed by infection and that flowering and survivorship of the infected plants decreased with reducing plant height. Since light availability affected plant growth and thereby flowering and survivorship, the differences in population dynamics between the two field sites could be caused by the differences in light environments. Although populations in open sites may persist for considerable periods after virus epidemics, the individual local populations of E. makinoi would eventually become extinct irrespective of light environments.

Mutagenic properties of estrogen quinone-derived DNA adducts in simian kidney cells.

DNA damage caused by catechol estrogens has been shown to play an etiologic role in tumor formation. Catechol estrogens are reactive to DNA and form several DNA adducts via their quinone forms. To explore the mutagenic properties of 2-hydroxyestrogen-derived DNA adducts in mammalian cells, N(2)-(2-hydroxyestrogen-6-yl)-2'-deoxyguanosine and N(6)-(2-hydroxyestrogen-6-yl)-2'-deoxyadenosine adducts induced by quinones of 2-hydroxyestrone, 2-hydroxyestradiol, or 2-hydroxyestriol were incorporated site-specifically into the oligodeoxynucleotides ((5)(')TCCTCCTCXCCTCTC, where X is dG, dA, 2-OHE-N(2)-dG, or 2-OHE-N(6)-dA). The modified oligodeoxynucleotides were inserted into single-stranded phagemid vectors followed by transfection into simian kidney (COS-7) cells. Preferential incorporation of dCMP, the correct base, was observed opposite all 2-OHE-N(2)-dG adducts. Only targeted G --> T transversions were detected; the highest mutation frequency (18.2%) was observed opposite the 2-OHE(2)-N(2)-dG adduct, followed by 2-OHE(1)-N(2)-dG (4.4%) and 2-OHE(3)-N(2)-dG (1.3%). When 2-OHE-N(6)-dA adducts were used, preferential incorporation of dTMP, the correct base, was observed. Targeted mutations representing A --> T transversions were detected, accompanied by small numbers of A --> G transitions. The highest mutation frequencies were observed with 2-OHE(1)-N(6)-dA and 2-OHE(3)-N(6)-dA (14.5 and 14.1%, respectively), while 2-OHE(2)-N(6)-dA exhibited a mutation frequency of only 6.0%. No mutations were detected with vectors containing unmodified oligodeoxynucleotides. Thus, 2-OHE quinone-derived DNA adducts are mutagenic, generating primarily G --> T and A --> T mutations in mammalian cells. The mutational frequency varied depending on the nature of the 2-OHE moiety.

Separate localization of light signal perception for sun or shade type chloroplast and palisade tissue differentiation in Chenopodium album.

Physiological and ecological characteristics of sun and shade leaves have been compared in detail, but their developmental processes, in particular their light sensory mechanisms, are still unknown. This study compares the development of sun and shade leaves of Chenopodium album L., paying special attention to the light sensory site. We hypothesized that mature leaves sense the light environment, and that this information determines anatomy of new leaves. To examine this hypothesis, we shaded plants partially. In the low-light apex treatment (LA), the shoot apex with developing leaves was covered by a cap made of a shading screen and received photosynthetically active photon flux density (PPFD) of 60 micromol m(-2 )s(-1), while the remaining mature leaves were exposed to 360 micromol m(-2 )s(-1). In the high-light apex treatment (HA), the apex was exposed while the mature leaves were covered by a shade screen. After these treatments for 6 d, we analyzed leaf anatomy and chloroplast ultrastructure. The anatomy of LA leaves with a two-layered palisade tissue was similar to that of sun leaves, while their chloroplasts were shade-type with thick grana. The anatomy of HA leaves and shade leaves was similar and both had one-layered palisade tissue, while chloroplasts of HA leaves were sun-type having thin grana. These results clearly demonstrate that new leaves differentiate depending on the light environment of mature leaves, while chloroplasts differentiate depending on the local light environment.

Identification of tamoxifen-DNA adducts induced by alpha-acetoxy-N-desmethyltamoxifen.

Treatment with tamoxifen increased the risk of endometrial cancers in breast cancer patients and women participating in the chemoprevention study. In our laboratory, tamoxifen-DNA adducts, including alpha-(N(2)-deoxyguanosinyl)tamoxifen (dG-N(2)-TAM), were detected in the endometrium of women taking tamoxifen [Shibutani, S., et al. (1999) Chem. Res. Toxicol. 12, 646-653]. On the basis of recent animal studies, deoxyguanosinyl-N-desmethyltamoxifen (dG-N-desmethylTAM) adducts are also suspected to be formed in the liver. In the study presented here, we synthesized alpha-acetoxy-N-desmethyltamoxifen as a model activated metabolite of N-desmethyltamoxifen. The overall yield of alpha-acetoxy-N-desmethyltamoxifen from alpha-hydroxytamoxifen was approximately 42%. alpha-Acetoxy-N-desmethyltamoxifen was highly reactive to 2'-deoxyguanosine, as was similarly observed for tamoxifen alpha-sulfate. The two reaction products were identified as a mixture of epimers of the trans form or cis form of alpha-(N(2)-deoxyguanosinyl)-N-desmethyltamoxifen (dG-N(2)-N-desmethylTAM) by mass and proton magnetic resonance spectroscopy. In addition, the trans and cis forms of dG 3'-monophosphate-N(2)-N-desmethylTAM were prepared as standard markers for (32)P-postlabeling/HPLC analysis. Using this technique, dG-N(2)-N-desmethylTAM adducts were detected in calf thymus DNA reacted with alpha-acetoxy-N-desmethyltamoxifen.

Identification of tamoxifen-DNA adducts in the endometrium of women treated with tamoxifen.

The risk of developing endometrial cancer increases significantly for women treated with tamoxifen (TAM); the present study was designed to investigate the mechanism of this carcinogenic effect. Endometrial tissue was obtained from 16 women treated for varying lengths of time with TAM and from 15 untreated control subjects. DNA was analyzed with a (32)P-post-labeling/HPLC on-line monitoring assay capable of detecting 2.5 adducts/10(10) nucleotides. Using this sensitive and specific assay, TAM-DNA adducts were detected in eight women. The major adducts found were trans and cis epimers of alpha-(N(2)-deoxyguanosinyl) tamoxifen (dG-N(2)-TAM); levels ranged between 0.2-12 and 1.6-8.3 adducts/10(8) nucleotides, respectively. There was marked inter-individual variation in the relative amounts of cis and trans adducts present. Low levels (0.74-1.1 adducts/10(8) nucleotides) of trans and cis forms of dG-N(2)-TAM N-oxide were detected in one patient. DNA adducts derived from 4-hydroxytamoxifen quinone methide were not observed. We conclude from this analysis that trans and cis dG-N(2)-TAMs accumulate in significant amounts in the endometrium of many, but not all, women treated with this drug. The level of adducts found, coupled with the previous demonstration of their mutagenicity [Cancer Res., 59, 2091, 1999], suggest that a genotoxic mechanism may be responsible for TAM-induced endometrial cancer.

Acclimation of leaf characteristics of Fagus species to previous-year and current-year solar irradiances.

To examine the effects of different solar irradiances on leaf characteristics at the leaf primordium and expansion stages, we shaded parts of branches in the upper canopies of two adult beech trees, Fagus crenata Blume and Fagus japonica Maxim., for 4 years. The treatments during the leaf primordium and leaf expansion stages, respectively, were: (1) high light and high light (H, control), (2) high light and low light (HL), (3) low light and low light (LL), and (4) low light and high light (LH). Both number of cell layers in palisade tissue and individual leaf area were affected by the previous-year irradiance, whereas cell length of palisade tissue was larger in LH leaves than in LL leaves, suggesting determination by current-year irradiance. Lamina chlorophyll/nitrogen ratio was higher in HL and LL leaves than in LH leaves, suggesting determination by current-year irradiance. Diurnal minimum values of leaf water potential measured under sunlit conditions were lower in H and LH leaves than in HL and LL leaves. Effective osmotic adjustment was found in H and LH leaves, suggesting that leaf water relations were affected by current-year irradiance. Net photosynthetic rate and stomatal conductance measured under sunlight conditions were higher in H and LH leaves than in HL and LL leaves. Thus, effects of current-year irradiance had a greater effect on leaf-area-based daily carbon gain than previous-year irradiance.

[Influence of dexamethasone on the clinical course of bacterial meningitis in children. Especially on secondary fever. Experiences in 27 institutions].

Of pediatric patients with purulent meningitis seen at the institutions listed in the title page of this paper between 1986 and 1994, 93 patients treated with antibiotics and dexamethasone (DXM) were compared with 91 patients treated with antibiotics alone. The patients receiving antibiotics with dexamethasone achieved overall improvement in inflammatory symptoms and signs and cerebrospinal fluid findings and became afebrile significantly earlier than those receiving antibiotics alone. However, some of the patients became febrile again. The secondary fever rate for the DXM group was much higher than that for the antibiotic alone group (p < 0.0001). In most of the rebounded cases, the body temperature rose above 38 degrees C and remained elevated for 2-4 days. Cerebrospinal fluid (CSF) was cultured daily in 54 and 32 patients receiving antibiotics with and without DXM, respectively. Although this study was not a controlled study in a strict sense, these patients compared. In both groups, the CSF became mostly culture-negative within 48 hours. In a few patients receiving DXM, however, it became culture-negative after 72 hours or longer. DXM caused an adverse effect in a patient with meningitis caused by Streptococcus pneumoniae. The adverse effect was mild gastrointestinal bleeding, which recovered spontaneously. From the findings described above, the use of DXM combined with antibiotic therapy was considered to accelerate the relief from fever and improvement of inflammatory symptoms and signs and CSF findings. The body temperature rose again in more than half of the patients receiving DXM, but fell to normal spontaneously without treatment. The elevation doubtlessly could not be distinguished from recurrence of the meningitis itself or complications. It seems to be likely that no treatment but careful observation is required even if the fever recurs as far as the CSF findings showed favorable progress with excelluent general conditions. When DXM is given, it is essential that CSF tests and culture are repeated during the early stages and the progress is monitored carefully.

Tamoxifen-DNA adducts detected in the endometrium of women treated with tamoxifen.

Women treated for breast cancer with tamoxifen are at increased risk of developing endometrial cancer. This carcinogenic effect has been attributed to estrogenic stimulation and/or to a genotoxic effect of this drug. To examine genotoxicity, we developed a (32)P-postlabeling TLCL/HPLC procedure for quantitative analysis of tamoxifen-DNA adducts in endometrial tissue. This assay is several orders of magnitude more sensitive than those previously used for this purpose; with it, we can detect five tamoxifen-DNA adducts in 10(11) bases. Endometrial tissue was obtained from women undergoing tamoxifen therapy and from untreated control subjects. DNA adducts, identified as trans and cis epimers of alpha-(N(2)-deoxyguanosinyl)tamoxifen, were detected in six of thirteen patients in the tamoxifen-treated group. Levels of trans and cis adducts ranged from 0.5 to 8.3 and from 0.4 to 4.8 adducts/10(8) nucleotides, respectively. Tamoxifen-DNA adducts were not detected in endometrial tissue obtained from the control subjects. We conclude from this study that one or more tamoxifen metabolites react with endometrial DNA to form covalent adducts, establishing the potential genotoxicity of this drug for women and suggesting the use of TAM-DNA adducts as biomarkers for investigations of tamoxifen-induced endometrial cancer.

Mutagenic potential of alpha-(N2-deoxyguanosinyl)tamoxifen lesions, the major DNA adducts detected in endometrial tissues of patients treated with tamoxifen.

Breast cancer patients treated with the antiestrogen tamoxifen (TAM) show an increased risk of developing endometrial cancer. We have recently detected TAM-DNA adducts in endometrium obtained from patients treated with TAM and identified them as trans- and cis-forms of alpha-(N2-deoxyguanosinyl)tamoxifen (dG-N2-TAM). To explore the mutagenic properties of these TAM-DNA adducts, we prepared site-specifically modified oligodeoxynucleotides containing a single isomer of dG-N2-TAM by reacting a 15-mer oligodeoxynucleotide containing a single dG (5'-TCCTCCTCGCCTCTC) with tamoxifen alpha-sulfate. These modified oligodeoxynucleotides were inserted into a single-stranded shuttle vector to investigate mutagenic specificities of the adducts in simian kidney (COS-7) cells. An epimer of dG-N2-trans-TAM showed targeted mutations ranging from 0.7 to 1.5%. The other dG-N2-trans-TAM adduct showed 9.6% G-->T transversions, accompanied by 2.8% G-->A transitions. Both dG-N2-cis-TAM adducts showed similar mutation spectra, where G-->T transversions (11-12%) predominated, along with a small number of G-->A transitions and G-->C transversions. Thus, dG-N2-TAMs are mutagenic lesions in mammalian cells. The tamoxifen-DNA adducts detected in patient endometrium may cause mutations and initiate endometrial cancer.

Effective utilization of N2-ethyl-2'-deoxyguanosine triphosphate during DNA synthesis catalyzed by mammalian replicative DNA polymerases.

Acetaldehyde is produced by metabolic oxidation of ethanol after drinking alcoholic beverages. This agent reacts with nucleosides and nucleotides, resulting in the formation of N2-ethyl-guanine residues. N2-ethyl-2'-deoxyguanosine (N2-ethyl-dG) adduct has been detected in the lymphocyte DNA of alcoholic patients [Fang, J. L., and Vaca, C. E. (1997) Carcinogenesis 18, 627-632]. Thus, the nucleotide pool is also expected to be modified by acetaldehyde. N2-Ethyl-2'-deoxyguanosine triphosphate (N2-ethyl-dGTP) was chemically synthesized. The utilization of N2-ethyl-dGTP during DNA synthesis was determined by steady-state kinetic studies. N2-Ethyl-dGTP was efficiently incorporated opposite template dC in reactions catalyzed by mammalian DNA polymerase alpha and delta. When pol alpha was used, the insertion frequency of N2-ethyl-dGTP was 400 times less than that of dGTP, but 320 times higher than that of 7,8-dihydro-8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dGTP), an oxidative damaged nucleotide. Using pol delta, the insertion frequency of N2-ethyl-dGTP was only 37 times less than that of dGTP. The chain extension from dC:N2-ethyl-dG pair occurred much more rapidly: the extension frequencies for pol alpha and pol delta were only 3.8 times and 6.3 times, respectively, lower than that of dC:dG pair. We also found that N2-ethyl-dG can be detected in urine samples obtained from healthy volunteers who had abstained from drinking alcohol for 1 week before urine collection. This indicates that humans are exposed constantly to acetaldehyde even without drinking alcoholic beverages. Incorporation of N2-ethyl-dG adducts into DNA may cause mutations and may be related to the development of alcohol- and acetaldehyde-induced human cancers.

Sulfation of alpha-hydroxytamoxifen catalyzed by human hydroxysteroid sulfotransferase results in tamoxifen-DNA adducts.

The formation of tamoxifen (TAM)-derived DNA adducts was investigated by incubation of DNA with (E)-alpha-hydroxytamoxifen [(E)-alpha-OHTAM], 3'-phosphoadenosine 5'-phosphosulfate (PAPS), and human recombinant sulfotransferase. Using 32P-post-labeling and HPLC analysis, two TAM-DNA adducts were detected in incubations that included the human hydroxysteroid sulfotransferase SULT2A1 (hHST). When compared with standards of stereoisomers of alpha-(N2-deoxyguanosinyl)tamoxifen 3'-monophosphate (dG3'P-N2-TAM), the major adduct was identified chromatographically as an epimer of the transform of dG-N2-TAM, and the minor adduct was identified as an epimer of the cis-form. The amount of TAM adducts formed by hHST was approximately three times less than that formed by an equivalent amount of rat hydroxysteroid (alcohol) sulfotransferase a. These results indicate that sulfation of alpha-OHTAM catalyzed by hHST results in the formation of dG-N2-TAMs, highly miscoding lesions, in human tissues.

Molecular cloning of AtMMH, an Arabidopsis thaliana ortholog of the Escherichia coli mutM gene, and analysis of functional domains of its product.

We isolated and characterized cDNAs and a genomic clone encoding an Arabidopsis thaliana MutM homolog (AtMMH). AtMMH is a single-copy gene spanning about 3 kb in the nuclear genome, and comprises ten exons. The AtMMH gene encodes two types of mRNA (AtMMH-1 and AtMMH-2) formed by alternative splicing of exon 8. Western analysis of a crude extract from leaves of A. thaliana, using polyclonal antibodies against the recombinant proteins, demonstrated the presence in vivo of a single 44-kDa polypeptide that comigrates with the product of in vitro translation of the AtMMH-1 mRNA. AtMMH-1 protein prepared in vitro is able to nick double-stranded oligonucleotides containing 8-oxo-7,8-dihydroguanine (8-oxoG) and to bind such oligonucleotides, as does the Escherichia coli MutM protein, which possesses 8-oxoG DNA glycosylase and apurinic/apyrimidinic (AP) lyase activities. Deletion of six amino acids (PELPEV), which are conserved among all known MutM homologs, from the N-terminal end of the AtMMH-1 protein abolishes its nicking but not its DNA-binding activity, indicating that these residues are essential for catalytic activity. Although the AtMMH-1 protein has a unique structure at its C-terminal end, which consists of alternating repeats of basic and acidic amino acids, this structure is dispensable for activity. However, the adjacent amino acid sequence (residues 268 to 281) is essential for repair activity.

Translesional synthesis on DNA templates containing an estrogen quinone-derived adduct: N2-(2-hydroxyestron-6-yl)-2'-deoxyguanosine and N6-(2-hydroxyestron-6-yl)-2'-deoxyadenosine.

Miscoding properties induced by estrogen quinone-derived DNA adducts were analyzed using an in vitro experimental system to quantify base substitutions and deletions. Site-specifically modified oligodeoxynucleotides containing a single N2-(2-hydroxyestron-6-yl)-2'-deoxyguanosine (2-OHE1-N2-dG) or N6-(2-hydroxyestron-6-yl)-2'-deoxyadenosine (2-OHE1-N6-dA) were prepared postsynthetically and used as templates in primer extension reactions catalyzed by mammalian DNA polymerases (pol) alpha, beta, and delta. The 2-OHE1-N2-dG adduct blocked primer extension reactions more strongly than 2-OHE1-N6-dA. Using pol alpha and delta, 2-OHE1-N2-dG promoted incorporation of dCMP (6.3 and 3.1%, respectively), the correct base, opposite the lesion: when pol delta was used, misincorporation of dTMP (0.52%) was detected. 2-OHE1-N6-dA also promoted incorporation of dTMP, the correct base, opposite the lesion, accompanied by misincorporation of dCTP (0.54% for pol alpha and 3.2% for pol delta) and one-base deletion (0.3-0.5%). Using pol beta, no miscoding was detected. The miscoding occurred only when replicative DNA polymerases were used. Kinetic data were consistent with those obtained from the analysis of fully extended products formed by pol alpha or pol beta. These results indicate that endogenous estrogen quinone-derived DNA adducts have miscoding potential: G --> A and A --> G transitions and deletions are predicted in mammalian cells.