Performance of a Point of Care Test for Detecting IgM and IgG Antibodies Against SARS-CoV-2 and Seroprevalence in Blood Donors and Health Care Workers in Panama

Novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic, which has reached 28 million cases worldwide in 1 year. The serological detection of antibodies against the virus will play a pivotal role in complementing molecular tests to improve diagnostic accuracy, contact tracing, vaccine efficacy testing, and seroprevalence surveillance. Here, we aimed first to evaluate a lateral flow assay's ability to identify specific IgM and IgG antibodies against SARS-CoV-2 and second, to report the seroprevalence estimates of these antibodies among health care workers and healthy volunteer blood donors in Panama. We recruited study participants between April 30th and July 7th, 2020. For the test validation and performance evaluation, we analyzed serum samples from participants with clinical symptoms and confirmed positive RT-PCR for SARS-CoV-2, and a set of pre-pandemic serum samples. We used two by two table analysis to determine the test positive and negative percentage agreement as well as the Kappa agreement value with a 95% confidence interval. Then, we used the lateral flow assay to determine seroprevalence among serum samples from COVID-19 patients, potentially exposed health care workers, and healthy volunteer donors. Our results show this assay reached a positive percent agreement of 97.2% (95% CI 84.2-100.0%) for detecting both IgM and IgG. The assay showed a Kappa of 0.898 (95%CI 0.811-0.985) and 0.918 (95% CI 0.839-0.997) for IgM and IgG, respectively. The evaluation of serum samples from hospitalized COVID-19 patients indicates a correlation between test sensitivity and the number of days since symptom onset; the highest positive percent agreement [87% (95% CI 67.0-96.3%)] was observed at ≥15 days post-symptom onset (PSO). We found an overall antibody seroprevalence of 11.6% (95% CI 8.5-15.8%) among both health care workers and healthy blood donors. Our findings suggest this lateral flow assay could contribute significantly to implementing seroprevalence testing in locations with active community transmission of SARS-CoV-2.

Probable long-term prevalence for a predominant Mycobacterium tuberculosis clone of a Beijing genotype in Colon, Panama

Beijing genotype Mycobacterium tuberculosis strains associate with increased virulence, resistance and/or higher transmission rates. This study describes a specific Beijing strain predominantly identified in the Panamanian province of Colon with one of the highest incidences of tuberculosis in the country. Retrospective mycobacterial interspersed repetitive unit/variable number of tandem repeats analysis of 42 isolates collected between January and August 2018 allowed to identify a cluster (Beijing A) with 17 (40.5%) Beijing isolates. Subsequent prospective strain-specific PCR-based surveillance from September 2019 to March 2020 confirmed the predominance of the Beijing A strain (44.1%) in this province. Whole-genome sequencing revealed higher-than-expected diversity within the cluster, suggesting long-term prevalence of this strain and low number of cases caused by recent transmission. The Beijing A strain belongs to the Asian African 3 (Bmyc13, L2.2.5) branch of the modern Beijing sublineage, with their closest isolates corresponding to cases from Vietnam, probably introduced in Panama between 2000 and 2012.

Case Report: COVID-19 Recovery from Triple Infection with Mycobacterium tuberculosis, HIV, and SARS-CoV-2

COVID-19, designated as SARS-CoV-2, has caused millions of infections worldwide, including in patients with concomitant infections. Here, we report two unusual cases of patients with triple infections of SARS-CoV-2, Mycobacterium tuberculosis, and HIV. Both cases were confirmed through microbiological and immunological studies. The acute respiratory phase in both patients was treated with supplemental oxygen. Antituberculosis and antiretroviral therapies were started simultaneously. In 2 weeks, both patients demonstrated clinical improvement and recovery from COVID-19. Our findings suggest that even in cases of triple infection, clinical management together with respiratory therapy contributes to patient survival.

Reduced Food Intake Among Tuberculosis Patients Within an Urban Setting in Panama (P10-023-19)

Objectives

The aim of our study is to characterize the dietary factors and food items intake of people living with pulmonary tuberculosis in an urban and high disease incidence city in Panama.

Methods

We recruited 41 participants newly diagnosed with pulmonary tuberculosis. We applied a culturally adapted version of the NHANES Food Screener to estimate dietary median intakes and to evaluate daily and weekly frequencies of consumption. All frequencies reported were converted to daily frequency to describe the dietary patterns and make estimations. Direct observed anti-tuberculosis therapy was provided to all participants.

Results

Among the participants, 20% were female, the average age was 38.9 years old, the average body mass index was 20.4 and 16% were patients living with HIV. When comparing the consumption frequency reported by the TB patients with the Panamanian Dietary recommendations, these patients did not meet the minimal frequency intake of fruit and whole grain. Only 30% of participants achieved the recommended fruit frequency intake. We also found that only 37% of participants meet the recommended consumption of at least 3 times a week of beans and legumes. In contrast, a high number of these TB patients (34/41) reported a daily vegetable intake frequency and a mean of 25 teaspoons of added sugar daily intake. For sugar-sweetened beverages intake, we found a mean frequency intake of twice a day and 73% of our participants had a daily consumption of any dairy product. A total of 63% of our participants reported consumption of processed meat more than twice a week.

Conclusions

The food intake pattern in patients suffering tuberculosis includes daily consumption of vegetables, frequent consumption of dairy products and sport or fruit drinks, but a low frequency of fruits, beans, and legumes. These findings suggest that the protective dietary factors including fruits and whole grain are not consumed at the minimum requirement intake to improve general health in our patient group. We recommend decreasing processed meat intake among patients suffering tuberculosis. Also, we recommend the use of diet supplementation programs to improve anti-tuberculosis treatment success rates. Food security investigations to determine the extent of limitations to access healthy food remain key for improving disease control.

Funding Sources

Secretaria Nacional de Ciencia y Tecnologia de Panama (SENACYT).

The treatment with the probiotic Shewanella putrefaciens Pdp11 of specimens of Solea senegalensis exposed to high stocking densities to enhance their resistance to disease

Aquaculture industry exposes fish to acute stress events, such as high stocking density, and a link between stress and higher susceptibility to diseases has been concluded. Several studies have demonstrated increased stress tolerance of fish treated with probiotics, but the mechanisms involved have not been elucidated. Shewanella putrefaciens Pdp11 is a strain isolated from healthy gilthead seabream (Sparus aurata L.) and it is considered as probiotics. The aim of this study was to evaluate the effect of the dietary administration of this probiotics on the stress tolerance of Solea senegalensis specimens farmed under high stocking density (PHD) compared to a group fed a commercial diet and farmed under the same conditions (CHD). In addition, during the experiment, a natural infectious outbreak due to Vibrio species affected fish farmed under crowding conditions. Changes in the microbiota and histology of intestine and in the transcription of immune response genes were evaluated at 19 and 30 days of the experiment. Mortality was observed after 9 days of the beginning of the experiment in CHD and PHD groups, it being higher in the CHD group. Fish farmed under crowding stress showed reduced expression of genes at 19 day probiotic feeding. On the contrary, a significant increase in immune related gene expression was detected in CHD fish at 30 day, whereas the gene expression in fish from PHD group was very similar to that showed in specimens fed and farmed with the conventional conditions. In addition, the dietary administration of S. putrefaciens Pdp11 produced an important modulation of the intestinal microbiota, which was significantly correlated with the high number of goblet cells detected in fish fed the probiotic diet.

Angiotensin-converting enzyme gene single polymorphism as a genetic biomarker of diabetic peripheral neuropathy: longitudinal prospective study

BACKGROUND

Identifying patients at risk of developing diabetic peripheral neuropathy (DPN) is of paramount importance in those with type 2 diabetes mellitus (T2DM) to provide and anticipate secondary prevention measures as well as intensify action on risk factors, particularly so in primary care. Noteworthy, the incidence of DPN remains unknown in our environment.

AIMS

(i) To analyze a single angiotensin-converting enzyme (ACE) gene polymorphism (D/I) as a genetic marker of risk of developing DPN, and (ii) to determine the incidence of DPN in our environment.

RESEARCH DESIGN AND METHODS

Longitudinal study with annual follow-up for 3years involving a group of T2DM (N=283) randomly selected. ACE gene polymorphism distribution (I=insertion; D=deletion) was determined. DPN was diagnosed using clinical and neurophysiology evaluation.

RESULTS

Baseline DPN prevalence was 28.97% (95% CI, 23.65-34.20). ACE polymorphism heterozygous genotype D/I presence was 60.77% (95% CI, 55.05-66.5) and was independently associated with a decreased risk of DPN (RR, 0.51; 95% CI, 0.30-0.86). DPN correlated with age (P<0.001) but not with gender (P=0.466) or time of evolution of T2DM (P=0.555). Regarding end point, DPN prevalence was 36.4% (95% CI, 30.76-42.04), and accumulated incidence was 10.4% 3years thereafter. In the final Poisson regression analysis, the presence of heterozygous genotype remained independently associated with a decreased risk of DPN (RR, 0.71; (95% CI, 0.53-0.96). DPN presence remained correlated with age (P=0.002), but not with gender (P=0.490) or time of evolution (P=0.630).

CONCLUSIONS

In our series, heterozygous ACE polymorphism (D/I) stands as a protective factor for DPN development. Accumulated incidence of DPN was relevant. Further prospective studies are warranted.

Vascular endothelial growth factor receptor-2 (VEGFr-2) genetic polymorphisms as predictors to antiangiogenic therapy

e14561

Background: Vascular endothelial growth factor (VEGF) and its receptors (VEGFr-2) have important roles in angiogenesis, predicting risk and prognosis in several solids tumor. VEGFr-2 located on chromosome 4 (4q11-q12) is organized into 30 exons separated by 29 introns. Recently the VEGF-2578 AA and VEGF-1154 AA genotypes were associated with a superior median overall survival when using bevacizumab in metastatic breast cancer. We investigated the association of VEGFr-2 polymorphisms to efficacy and toxicity in patients with antiangiogenic therapy. Methods: We performed genotype for selected VEGFr-2 polymorphisms in promoter regions 5’UTR, 3’UTR; in exons 7, 8, 9, 11, 16, 17, 18, 21, 27, 30 and introns 9, 17, 20. DNA was extracted from venous blood of 44 patients with non-curable solid tumors who have received treatment with bevacizumab (B) N=20 (45%) or raf kinase inhibitors 55%; vatalanib (PTK-787) N=3, sunitinib (SU011248) N=6, sorafenib (BAY 43–9006) N= 13, ZD6474 N=1 and AMG706 N= 1. Kaplan-Meier survival analysis was used to assess the association between VEGFr-2 staining and either progression-free survival (PFS) or overall survival (OS). Results: 44 patients have received a median of 6 (1–19) cycles of treatment, 72% was used simultaneously with QT. According to the criteria of NCI-CTC the severe toxicity G3–4 occurred in 47%, 9% with a definite suspension of the drug. The toxicity was not associated with VEGFr-2 genotypes. Efficacy; 5/44 patients (11%) had complete response and 11/ 44 (22%) partial responses by RECIST criteria. With a median follow up of 12 months, the ILP was 8.5 months dt (5.8). The analysis of VEGFr-2 polymorphisms identifies the variant AA of the intron-20 rs2219471 with a significant difference in PFS and OS regarding their ancestral variant AG. Conclusions: Our data suggest that VEGFR polymorphism can be a predictor of clinical outcomes in antiangiogenic therapy.

No significant financial relationships to disclose.

Clinical screening and diagnosis of diabetic polyneuropathy: the North Catalonia Diabetes Study

BACKGROUND

To evaluate the prevalence of diabetic polyneuropathy (DPN) and develop a simple and accurate method for the evaluation of DPN risk in primary care settings.

MATERIALS AND METHODS

Cross-sectional descriptive study in a random sample (N = 307) of type 2 diabetes mellitus participants. DPN was diagnosed by both clinical neurological examination and simplified DPN Selection Method in each patient. Correlation between the two methods was obtained.

RESULTS

Prevalence of DPN was 23.13% (confidence interval,18.38-27.87) according to clinical neurological examination. Noteworthy, clinical neurological evaluation scores were related to nerve conduction studies (r = 0.882; P < 0.0005). DPN presence was positively related to age, metabolic control (HbA1c levels), known duration of diabetes, diabetic retinopathy, cardiovascular disease, peripheral ischemia and systolic and diastolic blood pressure, but was negatively related to current high-density lipoprotein cholesterol (HDL-C) levels (P < 0.0001). The sensitivity and specificity of our DPN Selection Method (using four clinical parameters: age, retinopathy, HbA1c and HDL-C plasma levels) for diagnosis of DPN was 74.20% and 74.90%, respectively.

CONCLUSIONS

The expected prevalence of DPN was observed. The sensitivity of the DPN Selection Method correlated well with formal clinical neurological exam in detection of the condition. We therefore conclude the DPN Selection Method is a useful tool in primary care settings in the evaluation and diagnosis of DPN.

Expression analysis of the nrdHIEF operon from Escherichia coli. Conditions that trigger the transcript level in vivo

Escherichia coli has two aerobic ribonucleotide reductases encoded by the nrdAB and nrdHIEF operons. While NrdAB is active during aerobiosis, NrdEF is considered a cryptic enzyme with no obvious function. Here, we present evidence that nrdHIEF expression might be important under certain circumstances. Basal transcript levels were dramatically enhanced (25-75-fold), depending on the growth-phase and the growth-medium composition. Likewise, a large increase of >100-fold in nrdHIEF mRNA was observed in bacteria lacking Trx1 and Grx1, the two main NrdAB reductants. Moreover, nrdHIEF expression was triggered in response to oxidative stress, particularly in mutants missing hydroperoxidase I and alkyl-hydroperoxide reductase activities (69.7-fold) and in cells treated with oxidants (up to 23.4-fold over the enhanced transcript level possessed by cells grown on minimal medium). The mechanism(s) that triggers nrdHIEF expression remains unknown, but our findings exclude putative global regulators like RpoS, Fis, cAMP, OxyR, SoxR/S, or RecA. What we have learned about nrdHIEF expression indicates strong differences between its regulation and that of the nrdAB operon and of genes coding for components of both thioredoxin/glutaredoxin pathways. We propose that E. coli might optimize the responses to different stimuli by co-evolving the expression levels for its multiple reductases and electron donors.

Interhospital observer agreement in interpretation of exercise myocardial Tc-99m tetrofosmin SPECT studies

BACKGROUND

We sought to determine the degree of interhospital agreement in the interpretation of exercise myocardial technetium-99m tetrofosmin single photon emission computed tomography (SPECT).

METHODS AND RESULTS

Five experienced hospital laboratories were asked to submit 2 sets of myocardial Tc-99m tetrofosmin SPECT images obtained in 150 patients undergoing coronary angiography: group A used a uniform color scale for all hospitals, and group B used the individual color scale in place at each hospital (uniform color scale, nonuniform color scale, and black-and-white scale). Thus a total of 300 images were interpreted by each center without knowledge of any other patient data. Angiographically significant coronary artery disease (< or =50% diameter stenosis) was present in 90 patients (60%). By a majority decision (3 or more centers), the sensitivity was found to be similar for groups A and B (82% and 84%, respectively), but the specificity was significantly higher for group A (87% vs 73%; P =.021). Four or all 5 of the centers agreed on abnormal or normal results of SPECT images in 87% of patients in group A (kappa 0.626) and in 78% of patients in group B (kappa 0.528). The kappa value of 0.617 was obtained for the uniform color scale, 0.467 for the uniform black-and-white scale, and 0.444 for the nonuniform color scale. Agreement on the left anterior descending artery territory (81% for group A and 78% for group B) was similar to that of the right coronary artery territory (79% for A and 75% for B) and to that of the left circumflex artery territory (91% for A and 85% for B). Agreement was similar in patients with 1-, 2-, and 3-vessel coronary artery disease (91%, 88%, and 86% for group A and 81%, 82%, and 82% for group B, respectively).

CONCLUSIONS

In the interpretation of myocardial Tc-99m tetrofosmin SPECT images, good interinstitutional observer agreement was found, mainly when the uniform display method was adopted.

Comparison of the levels of 8-hydroxyguanine in DNA as measured by gas chromatography mass spectrometry following hydrolysis of DNA by Escherichia coli Fpg protein or formic acid

8-hydroxyguanine (8-OH-Gua) is one of many lesions generated in DNA by oxidative processes including free radicals. It is the most extensively investigated lesion, due to its miscoding properties and its potential role in mutagenesis, carcinogenesis and aging, and also to the existence of analytical methods using HPLC and gas chromatography mass spectrometry (GC/MS). Some studies raised the possibility of artifacts generated during sample preparation. We investigated several experimental conditions in order to eliminate possible artifacts during the measurement of 8-OH-Gua by GC/MS. Derivatization has been reported to produce artifacts by oxidation of guanine to 8-OH-Gua in acid-hydrolysates of DNA, although the extent of artifacts seems to depend on experimental conditions. For removal of 8-OH-Gua from DNA, we used either formic acid hydrolysis or specific enzymatic hydrolysis with Escherichia coli Fpg protein. Derivatization of enzyme-hydrolysates should not generate additional 8-OH-Gua because of the absence of guanine, which is not released by the enzyme, whereas guanine released by acid may be oxidized to yield 8-OH-Gua. The measurement of 8-OH-Gua in calf thymus DNA by GC/isotope-dilution MS (GC/IDMS) using these two different hydrolyses yielded similar levels of 8-OH-Gua. This indicated that no artifacts occurred during derivatization of acid-hydrolysates of DNA. Pyridine instead of acetonitrile and room temperature were used during derivatization. Pyridine reduced the level of 8-OH-Gua, when compared with acetonitrile, indicating its potential to prevent oxidation. Two different stable-isotope labeled analogs of 8-OH-Gua used as internal standards for GC/IDMS analysis yielded similar results. A comparison of the present results with the results of recent trials by the European Standards Committee for Oxidative DNA Damage (ESCODD) is also presented.

Transcriptional regulation of glutaredoxin and thioredoxin pathways and related enzymes in response to oxidative stress

We examined the in vivo expression of up to 16 genes encoding for components of both glutaredoxin and thioredoxin systems and for members of the OxyR and SoxRS regulons. We demonstrated that grxA (Grx1) transcription is triggered in bacteria lacking Trx1 (trxA) and GSH (gshA) in an OxyR-dependent manner. We also indicated that, unlike OxyR, SoxR is not constitutively activated in the oxidizing environment of trxA gshA mutants. We discovered that the lack of Trx1 plus GSH increases the steady-state levels of Trx reductase (trxB) and Trx2 (trxC) transcripts. This increase and the trxB and trxC up-regulation caused by the constitutive oxyR2 allele indicate that OxyR also plays a role in the regulation of the thioredoxin pathway. On the contrary, no change in the expression of genes for Trx1, Grx2, and Grx3 was observed. Transcription of nrdAB (RRase) was not induced by oxidative stress yet was induced by hydroxyurea (RRase inhibitor). Induction level was as the enhanced nrdAB basal expression of trxA grxA mutants, indicating that RRase operation without Trx1 and Grx1 must lead to disturbances sensed as those caused by hydroxyurea. We also demonstrated an inverse relation between nrdAB expression and that of genes coding for components of both glutaredoxin (grxA, gorA) and thioredoxin (trxB, trxC) systems.

Rat 7,8-dihydro-8-oxoguanine DNA glycosylase: substrate specificity, kinetics and cleavagemechanism at an apurinic site

Reactive oxygen species produce different lesions in DNA. Among them, 7,8-dihydro-8-oxoguanine (8-oxoG) is one of the major oxidative products implicated in mutagenesis. This lesion is removed from damaged DNA by base excision repair, and genes coding for 8-oxoG-DNA glycosylases have been isolated from bacteria, yeast and human cells. We have isolated and characterized the cDNA encoding the rat 8-oxoG-DNA glycosylase (rOGG1). Expression of the cDNA in the fgp mutY Escherichia coli double mutant allowed the purification of the untagged rOGG1 protein. It excises 8-oxoG from DNA with a strong preference for duplex DNA containing 8-oxoG:C base pairs. rOGG1 also acts on formamidopyrimidine (FaPy) residues, and the K m values on 8-oxoG and FaPy residues are 18.8 and 9.7 nM, respectively. When acting on an oligonucleotide containing an 8-oxoG residue, rOGG1 shows a beta-lyase activity that nicks DNA 3' to the lesion. However, rOGG1 acts on a substrate containing an apurinic site by a beta-delta elimination reaction and proceeds through a Schiff base intermediate. Expression of rOGG1 in E.coli fpg mutY suppresses its spontaneous mutator phenotype.

Role of DNA repair by (A)BC excinuclease and Ogt alkyltransferase in the final distribution of LacI-d mutations induced by N-butyl-N-nitrosourea in Escherichia coli

In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransferase (ATase) encoded by the constitutive ogt gene of Escherichia coli caused a marked increase in mutation induction by N-butyl-N-nitrosourea (BNU). Irrespective of the presence or absence of the Ogt ATase, little mutagenic response was detected in Uvr+ bacteria in the concentration range 0-8 mM BNU, indicating that most premutagenic DNA lesions induced at these concentrations are efficiently recognized and repaired by the nucleotide excision repair system. Increased susceptibility to mutagenesis by BNU was detected in Uvr- Ogt+ bacteria, but the Uvr- Ogt- double mutant exhibited much higher sensitivity. These data suggest that the Ogt ATase can replace to a great extent the repair capacity of the (A)BC excinuclease. Forward mutations induced by 6 mM BNU within the initial part of the lacI gene of E.coli were recovered from Uvr+ Ogt-, Uvr- Ogt+ and Uvr- Ogt- bacteria. A total of 454 independent mutations were characterized by DNA sequence analysis. The BNU-induced spectra were dominated by G:C-->A:T transitions, consistent with the major role of the O6-alkylguanine miscoding lesion in mutagenesis by alkylating agents. Specific sites for G:C-->A:T transitions were recovered more or less frequently in one genetic background versus the others, giving statistically significant differences among the spectra (P < 10(-6)). We examined the influence of DNA repair by (A)BC excinuclease and Ogt ATase on the 5'-flanking base associated with the BNU-induced G:C-->A:T transitions; preferences different from those previously reported for other alkylnitrosoureas were detected. We discuss how these differences might be caused by BNU producing branched chain derivatives, in addition to the expected linear chain adducts, and by possible preferences with respect to both the initial distribution of O6-butylguanine lesions and their repairability.

Antimutagenic role of base-excision repair enzymes upon free radical-induced DNA damage

As a consequence of oxidative stress, reactive oxygen species are generated in the cells. They interact with DNA and induce various modifications. Among them, oxidised purines (such as C8-oxoguanine and purines whose imidazole ring is opened), oxidised pyrimidines (such as thymine and cytosine glycols, ring saturated and fragmented pyrimidines), ethenobases and hypoxanthine. These various lesions have either miscoding properties or are blocks for DNA and RNA polymerases during replication and transcription, respectively. Most of these lesions are repaired by the base excision pathway in which the first step is mediated by specific DNA glycosylases. We review the various glycosylases involved in the repair of oxidised bases in Escherichia coli. The Fpg protein (formamidopyrimidine-DNA glycosylase) contains a zinc finger and excises oxidised purines whereas the Nth protein excises oxidised pyrimidines. The Nei protein excises a comparable spectra of pyrimidines and is believed to act as a back up enzyme to the Nth protein. The hypoxanthine-DNA glycosylase excises hypoxanthine residue and is one of the various activities of the AlkA protein (including formyluracil and ethenopurines residues). The Nfo protein was shown to have a novel activity that incises 5' to an alpha-deoxyadenosine residue (the anomer of deoxyadenosine formed by gamma-irradiation). The mechanism of action of the Fpg and Nth proteins are discussed. The properties of the human counterpart of the Fpg and Nth proteins the hNth and OGG1 proteins, respectively are also reviewed.

The ring fragmentation product of thymidine C5-hydrate when present in DNA is repaired by the Escherichia coli Fpg and Nth proteins

Various forms of oxidative stress, including gamma-radiolysis and UV irradiation, result in the formation of damaged bases. (5R)-Thymidine C5-hydrate is one of several modified nucleosides produced from thymidine under these conditions. N-(2-Deoxy-beta-D-erythro-pentofuranosyl)-N-3-[(2R)-hydroxyisobutyric acid]urea or alphaRT is the respective fragmentation product formed from (5R)-thymidine C5-hydrate upon hydrolysis. This modified nucleoside has potential mutagenic or lethal properties. No enzymatic activity responsible for the removal of alphaRT has been identified. We report here that when present in DNA, alphaRT is a substrate for two purified enzymes from Escherichia coli involved in the repair of oxidized bases: the Nth and the Fpg proteins. The Fpg protein removes the alphaRT lesion more efficiently than the Nth protein. This is the first example of efficient excision of a ring-opened form of a pyrimidine by the Fpg protein. The high efficacy of the Fpg protein suggests that it is likely to be involved in vivo in the excision of alphaRT. The kinetics of the reaction of the Fpg protein with DNA containing alphaRT suggest substrate inhibition. Duplex oligodeoxynucleotides containing alphaRT positioned opposite T, dG, dC, and dA were cleaved efficiently by both enzymes, although the profiles of activity of the two enzymes were different. The Nth enzyme preferentially excises alphaRT when opposite a dG, followed by alphaRT.dA, alphaRT. T, and alphaRT.dC. For the Fpg protein, the order is alphaRT.dC >/= alphaRT.dG approximately alphaRT.T > alphaRT.dA. Moreover, we show that human cell extract exhibits an activity that excises alphaRT from an oligonucleotide, suggesting that human homologues of the Nth and/or Fpg proteins could be involved in repair of this lesion in human cells.

Effect of single mutations on the structural dynamics of a DNA repair enzyme, the Escherichia coli formamidopyrimidine-DNA glycosylase--a fluorescence study using tryptophan residues as reporter groups

The effects on the structure dynamics of the Escherichia coli wild-type formamidopyrimidine-DNA glycosylase (Fpg) protein of the single mutations Lys57-->Gly (FpgK57G), Pro2-->Gly (FpgP2G) and Pro2-->Glu (FpgP2E) were studied by fluorescence techniques, namely: lifetime measurements and acrylamide quenching of the fluorescence of Trp residues. The fluorescence decays of Fpg and its mutant forms were analysed by the maximum-entropy method and lifetime distributions in the range 200 ps to 9 ns were obtained. The lifetime distribution profiles of FpgK57G, FpgP2G and FpgP2E are different from that of wild-type Fpg. Both dynamic and static quenching by acrylamide were observed for all the proteins. At 20 degrees C, the bimolecular collisional quenching rate constant of the FpgP2E fluorescence by acrylamide was only 0.8 M(-1) s(-1) as compared to about 1.4 M(-1) s(-1) for the three other proteins. At 6 degrees C, all the spectroscopic properties of these four proteins are about the same. The analysis of experimental data demonstrates that all three mutations induce a structural reorganization of the Fpg protein. However, only the P2E mutation lead to a reduced accessibility of some Trp residues to acrylamide quenching. It is concluded that the single P2E replacement induces a conformational change leading to a more rigid globular structure as opposed to the wild type and K57G and P2G mutations. The influence of the single mutations on the enzyme activities of the Fpg protein is discussed.

Influence of DNA repair by (A)BC excinuclease and Ogt alkyltransferase on the distribution of mutations induced by n-propyl-N-nitrosourea in Escherichia coli

In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransferase (ATase) encoded by the constitutive ogt gene of Escherichia coli caused a marked increment in mutation induction by N-propyl-N-nitrosourea (PNU). Irrespective of the presence or the absence of the Ogt ATase, little mutagenic response was detected in Uvr+ bacteria in the concentration range 0-8 mM PNU, indicating that most premutagenic DNA lesions induced at these concentrations are efficiently recognized and repaired by the nucleotide excision repair system. Some increased susceptibility to mutagenesis by PNU was detected in Uvr- Ogt+ bacteria, but the Uvr- Ogt- double mutant exhibited much higher sensitivity. These data suggest that the Ogt ATase can replace to a great extent the repair capacity of the (A)BC excinuclease. Forward mutations induced by 6 mM PNU within the initial part of the lacl gene were recovered from Uvr+ Ogt-, Uvr- Ogt+, and Uvr- Ogt- bacteria. A total of 439 independent mutations were characterized by DNA sequence analysis. The PNU-induced spectra were dominated by G:C-->A:T transitions, consistent with the major role of the O6-alkylguanine miscoding lesion in mutagenesis by alkylating agents. Specific sites for G:C-->A:T transitions were recovered more or less frequently in one genetic background versus the others, giving statistically significant differences among the spectra (P < 10(-6)). We examined the influence of DNA repair by (A)BC excinuclease and Ogt ATase on the 5'-flanking base and DNA-strand associated with the PNU-induced G:C-->A:T transitions. Preferences different from those previously reported for the ethylating (ENU) and methylating (MNU) analogs were detected. We indicate that these differences might be caused by the PNU possibility of giving iso-propyl adducts, in addition to the expected n-propyl adducts, and by possible preferences in the initial distribution of these lesions as well as in their repair by the (A)BC excinuclease and the Ogt ATase of E. coli.

Mutational specificity of aflatoxin B1. Comparison of in vivo host-mediated assay with in vitro S9 metabolic activation

An intrasanguineous host-mediated assay was used to determine the pattern of mutagenesis induced by the carcinogen aflatoxin B1 in the lacI gene of Escherichia coli recovered from rat liver. To investigate the influence of different types of metabolic activation, the mutation spectrum induced by AFB1 activated in vitro by a commercially prepared S9 microsomal fraction from Aroclor 1254-treated rats was also obtained. A total of 281 forward mutations affecting the N-terminal region of the lacI gene were characterized by DNA sequencing analysis. AFB1 induced similar type of mutations with similar site specificity when activated by the standard S9 fraction or by employing a rat host-mediated assay. These results indicate the ability of the in vitro S9 fraction to mimic the in vivo metabolism, suggesting that the same active metabolite, presumably AFB1 8,9-epoxide, is responsible for generating a similar pattern of DNA damage, as reflected in the similarity of mutational spectra. For both activation systems, most mutations (>90%) were base substitutions that occurred primarily at G:C pairs. Somewhat over one-half of G:C targeted substitutions were GC>TA transversions, other mutations being evenly divided between G:C>AT transitions and GC>CG transversions. The mutational specificity exhibited by activated AFB1 can be explained by incorporation of different bases opposite a single type of non-instructive lesion during error-prone DNA synthesis. To what extent the mutations are due to the main adduct (AFB1-N7-Gua), its imidazole-ring-opened derivative or an apurinic site remains unknown.

Mutational specificity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in the Escherichia coli lacl gene of O6-alkylguanine-DNA alkyltransferase-proficient and -deficient strains

Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the lacl gene of Escherichia coli were recovered from bacteria proficient (Ogt+ Ada+) and deficient (Ogt- Ada-) in O6-alkylguanine-DNA alkyltransferase activity. A CCNU dose of 1 mM was selected for DNA sequence analysis. A total of 245 induced mutations were characterized. The mutations were almost exclusively (95%) GC-->AT transitions, indicating that CCNU-induced mutations arose in bacteria primarily from misreplication of O6-chloroethylguanine, in total agreement with results obtained for monofunctional alkylating agents. The distribution of CCNU-induced GC-->AT mutations was significantly altered by the presence of DNA alkyltransferase activity (P = 0.01). In the Ogt+ Ada+ mutational spectrum, guanines flanked on both sides by A:T base-pairs were on average 2.8 times more likely to mutate than those flanked by G:C base-pairs on at least one side. This bias disappeared in the Ogt- Ada- genetic background, thereby providing evidence that O6-chloroethylated guanines adjacent to G:C base-pairs are better targets for bacterial alkyltransferase than those not adjacent to G:C base-pairs. We recently reported a similar bias for ethyl methanesulfonate, strengthening the idea that CCNU is acting as a simple ethylating compound. In summary, this paper presents for the first time evidence that DNA repair by O6-alkylguanine-DNA alkyltransferases plays a major role in removing lesions responsible for GC-->AT transitions induced by CCNU, influencing their ultimate distribution with respect to sequence context.

Role of classical nitroreductase and O-acetyltransferase on the mutagenicity of nifurtimox and eight derivatives in Salmonella typhimurium

This study investigates the mutagenicity of nifurtimox (NFX) and eight analogues in Salmonella typhimurium indicator strains that possess different levels of classical nitroreductase or O-acetyltransferase activities. The NFX analogues tested replace the 3-methyl-4-yl-tetrahydro-1,4-thiazine-1,1-dioxide group of the parent compound with the following other groups: indazol-1-yl (1G); pyrazol-1-yl (1B); benzimidazol-1-yl (1E); 1,2,4-triazol-4-yl (1D); 1-methyl-3-methylthio-1,2,4-triazol-4-yl-5-thione (1I); 3,5-bis(methylthio)-1,2,4-triazol-4-yl (1H); 1-adamantyl (ADA); and 4,6-diphenylpyridin-1-yl-2-one (1K). In the genetic backgrounds of the standard Ames tester strains TA98 and TA100, these bacteria combine the L-arabinose resistance forward mutation assay (Ara test) with a deficiency or overproduction of either nitroreduction or O-acetylation. The Ara test revealed, in agreement with previous findings, important differences between TA98 and TA100 and demonstrated, moreover, that these genetic differences are of significance in mutagenicity testing with nitrofuran compounds. The Ara test also indicated dissimilarities between the metabolic activation of NFX and its analogues, these compounds being classified in three different groups according to their mutagenicity toward strain BA14 (genetic background of TA98) and its derivatives. The first group included analogues (1G, 1E, 1I, and ADA) that showed similar mutagenic potency in all bacterial strains. These compounds are considered not to be substrates for both classical nitroreductase and O-acetyltransferase. The second group included compounds (analogues 1B and 1K, and the reference drug NFX) with increased mutagenicity toward the strain overproducing the classical nitroreductase, and/or reduced mutagenicity toward the corresponding deficient bacteria. These compounds are considered to be activated by the classical nitroreductase. The third group (analogues 1D and 1H) was activated by bacterial O-acetyltransferase, and consequently showed increased and decreased mutagenicity with the particular overproducer or deficient bacterial strain, as compared to their isogenic parentals. Previous reports have pointed out interest in NFX analogue 1H as a promising candidate for the replacement of NFX. The present study further enhances the putative interest of compound 1H, based on the different metabolic activation pathway exhibited by this analogue as compared to the parental drug, NFX.

Influence of DNA repair by ada and ogt alkyltransferases on the mutational specificity of alkylating agents

We investigated the influence of the alkyltransferases (ATases) encoded by the ada and ogt genes of Escherichia coli on the mutational specificity of alkylating agents. A new mutational assay for selection of supF- mutations in shuttle-vector plasmids was used. Treating plasmid-bearing bacteria with N-methyl-N-nitrosourea (MNU), N-ethyl-N-nitrosourea (ENU), and ethyl methanesulfonate (EMS) dramatically increased the mutation frequency (from 33-fold to 789-fold). The vast majority of mutations (89-100%) were G:C-->A:T transitions. This type of mutation increased in ada- (MNU) or ogt- (ENU) bacteria, suggesting that repair of O6-methylguanine by ada ATase and repair of O6-ethylguanine by ogt ATase contribute mainly to the decrease in G:C-->A:T transitions. The analysis of neighboring base sequences revealed an overabundance of G:C-->A:T transitions at 5'-GG sequences. The 5'-PuG bias increased in ATase-defective cells, suggesting that these sequences were not refractory to repair. G:C-->A:T transitions occurred preferentially in the untranscribed strand after in vivo exposure. That this strand specificity was detected even in bacteria devoid of ATase activity (ada- ogt-) and not after in vitro mutagenesis suggests a bias for damage induction rather than for DNA repair. Highly significant differences were found between the in vivo and in vitro incidences of G:C-->A:T substitutions at the two major hotspots, positions 123 (5'-GGG-3'; antisense strand) and 168 (5'-GGA-3'; sense strand). These results are explained by differences in the probability of formation of stem-loop structures in vivo and in vitro.

Mutagenicity testing in Salmonella typhimurium strains possessing both the His reversion and Ara forward mutation systems and different levels of classical nitroreductase or O-acetyltransferase activities

The induction of forward mutations to L-arabinose resistance (AraR) and of reversions to histidine prototrophy (His+) can be quantitatively compared in Salmonella typhimurium BA strains. The BA bacteria carry the araD531 allele required for the Ara assay and a his auxotrophy (hisD3052 or hisG46) required for the His assay. In this study, 2 new sets of BA indicator strains have been constructed in order to combine the Ara forward and the His reverse mutation assays of S. typhimurium with deficiency, or over-production, in either classical nitroreductase or O-acetyltransferase for mutagenicity testing of nitro-containing chemicals. Nine mutagens with different chemical structures were tested to compare the specific mutagenic sensitivities of the new constructions with those of the parental and of the conventional TA indicator bacteria. The Ara test, which responded with high sensitivity to all chemicals tested, revealed important differences between the standard tester strains TA98 and TA100 with respect to the activation of mutagens considered to be dependent on classical nitroreductase activity. Total correspondence was found between the specific mutagenic sensitivities of the defective and the overproducing bacteria in the genetic background of TA98 but not in that of TA100. In the genetic background of TA100, chemicals such as nitrofurantoin and nitrofurazone displayed 10-fold reduced mutagenicity to the "classical nitroreductase" defective strain without increasing mutagenicity to the corresponding overproducing bacteria. This discrepancy might be attributed to the greater nitroreduction capability of strain TA100 (68.12 nmole/min/mg protein) as compared to TA98 (24.42 nmole/min/mg protein), by assuming that nitrofurantoin and nitrofurazone are such good substrates for classical nitroreductase that the additional enzyme activity produced from the corresponding overexpressing plasmid when present in TA100 no longer affected their metabolic activation. We propose that the Ara forward mutation test carried out in the set of over-producing bacteria constructed in the genetic background of TA98 might play a role for routine testing of large number of samples. The isogenic defective strains could be used in cases of uncertain results with the corresponding over-producing bacteria. Finally, the reversion of the his alleles accompanying the Ara assay in the BA strains could play a role in assessing the presence of mixtures of chemicals with different mutagenic specificity in samples of environmental relevance such as urban air, foods, and water.

Genetic differences between the standard Ames tester strains TA100 and TA98

The standard Ames tester strains of Salmonella typhimurium are separated by many steps in their pedigree, some involving mutagen treatments, and contain independently isolated uvrB-bio-gal deletions and rfa mutations. In this work the araD531 mutation was introduced into the Ames tester strains TA100 and TA98. The responsiveness of the resulting strains (BA15 and BA14) to a number of chemical mutagens was then assessed by monitoring the induction of forward mutations to L-arabinose resistance (Ara test). Here we have shown that these two strains of the Ames test differ greatly in their responses to mutagens, in ways that are not associated with the mutagenic specificities of the original his mutations. In general, the genetic background of strain TA100 appears to be more sensitive to the killing effects of chemicals than that of TA98. The greatest differences were found with nifurtimox (NFX) and its analogue, compound 1K. The Ara test responded to the mutagenic effects of these two nitrofurans when carried out in the genetic background of strain TA98 but not in that of TA100. A higher sensitivity to the lethal effects of NFX and 1K together with the greater nitro-reduction capability of strain TA100 as compared with TA98 might explain the differences. In conclusion, our results indicate that the standard Ames S. typhimurium tester strains are not isogenic and that genetic differences at loci other than his might be significant for mutagenicity testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Study on the mutagenic activity of 13 bioflavonoids with the Salmonella Ara test

The mutagenicity of 13 flavonoids has been investigated with the L-arabinose forward mutation assay of Salmonella typhimurium. Each flavonoid was tested by both plate incorporation and preincubation mutagenesis protocols in the presence or the absence of mammalian metabolic activation (S9 mixture). All flavonoids gave a dose-response relationship and induced a number of AraR mutants considered statistically significant. Their minimum mutagenic doses (MMD) differed markedly in the Ara test, covering a 400-fold range: from 4 nmol for quercetin to 1626 nmol for taxifolin. Flavonols were the strongest mutagens, with mutagenic potencies (MMD-1) representing from 27 to approximately 2% that of quercetin. Comparatively, the mutagenicities of other flavonoids represented only less than or equal to 1%. The data reported in this paper for the Ara forward mutation test suggest structural requirements for mutagenicity of bioflavonoids like those previously reported for the His reverse mutation assay: (i) flavonols with a free hydroxyl at position 3 are the strongest mutagenic flavonoids, (ii) saturation of the 2,3 double bond diminishes the mutagenic potency, and (iii) free hydroxyl groups at positions 3' and 4' influence the non-requirement for metabolic activation. The mutagenic properties of quercetin and rutin in the Ara test support the idea that these flavonols are not the major putative mutagens in complex mixtures such as wine.

Autologous adrenal medullary transplants in advanced Parkinson's disease with particular attention to the selective improvement in symptoms

Ten patients with advanced Parkinson's disease, presenting with tremor, rigidity and akinesia had autologous adrenal medullary transplantation taken from the left adrenal gland to the head of the right caudate nucleus. Particular attention was taken to avoid prolonged exposure of the adrenal tissue before transplantation and to separate the medullary from the cortical adrenal tissues. Postoperative CT scans confirmed the correct position of the transplants. Differences between pre- and 1-year postoperative clinical conditions were statistically evaluated, with patients under medical (L-dopa) treatment and after the medication was temporarily discontinued. Performance of motor tasks was tested to differentiate slowness of movements imposed by excessive muscular tension (rigidity) from that secondary to delayed reaction time to sensory demands (akinesia). Two deaths occurred 35 and 69 day after surgery for causes not related to the surgical procedures. One of those patients had remained stable neurologically and the other had deteriorated to progressive dementia and catatonia. At autopsy, no lesions in the CNS other than those expected from the surgical procedure were evident, and histological examination failed to reveal chromaffin cells in the head of the right caudate nucleus. Evaluation of the 8 cases that survived for 1 year revealed no significant improvement in their clinical or motor task performance, when considered as a group. However, cases with mild akinesia did better than cases with moderate to advanced akinesia, suggesting that transplantation is indicated in cases with rigidity, but not in cases with 'negative' symptoms of Parkinson's disease. All cases required postoperative medication.

Mycobacterium chelonei iatrogenic infections

We report on two outbreaks of Mycobacterium chelonei subsp. abscessus cutaneous infections, which occurred between June 1974 and April 1975 in a series of 24 patients (15 studied bacteriologically) subjected to venous stripping for varicose veins. The source of infection was the aqueous solution of merbromin used in presurgical care.

[Angiodysplasia of the colon]

The authors present a case review of a congenital abnormality of the inferior mesenteric blood vessels which resulted in ischemia of the descending colon and rectosigmoid area. The resulting colitis is only very rarely secondary to a vascular congenital abnormality. In this case, rectosigmoidoscopy, barioum study of the large bowel and a biopsy of the rectal mucosa pointed towards the ischemic nature of the lesion. This led to the selective angiographic study of the inferior mesenteric vessels with findings of a dilated inferior mesenteric artery and angiodysplasia. Surgical treatment included tying off of the inferior mesenteric artery and resection of the descending and rectosigmoid colon followed by transverse colon-rectum anastomosis. The angiographic and histopathologic studies were of great importance in establishing the true nature of the patient's clinical syndrome. One must keep in mind that the rectosigmoidoscopic findings may be seen in other disease states which do not have a vascular origin. These include Crohn's disease, severe amoebiasis and penumatosis of the intestine.