Spectrum of point mutations in the coding region of the hypoxanthine- guanine phosphoribosyltransferase (hprt) gene in human T-lymphocytes in vivo

The hypoxanthine-guanine phosphoribosyl transferase (hprt) locus in 6- thioguanine (TG) resistant T-lymphocytes is a useful target for the study of somatic in vivo mutagenesis, since it provides information about a broad spectrum of mutation. Mutations in the hprt coding region were studied in 124 TG-resistant T-cell clones from 38 healthy, non- smoking male donors from a previously studied population of bus maintenance workers, fine-mechanics and laboratory personnel. Their mean age was 43 years (range 23-64) and their hprt mutant frequency was 9.3 +/- 5.2 x 10(-6) (mean +/- SD, range 1.4-22.6 x 10(-6)). Sequence analysis of hprt cDNA identified 115 unique mutations; 76% were simple base substitutions, 10% were +/-1 bp frameshifts, and 10% were small deletions within exons (3-52 bp). In addition, two tandem base substitutions and one complex mutation were observed. Simple base substitutions were observed at 55 (20%) of 281 sites known to be mutable in the hprt coding sequence. The distribution of these mutations was significantly different than would be expected based upon a Poisson distribution (P < 0.0001), suggesting the existence of 'hotspots'. All of the 87 simple base substitutions occurred at known mutable sites, but eight were substitutions of a kind that have not previously been reported at these sites. The most frequently mutated sites were cDNA positions 197 and 146, with six and five independent mutations respectively. Four mutations were observed at position 131, and three each at positions 143, 208, 508 and 617. Transitions (52%) were slightly more frequent than tranversions (48%), and mutations at GC base pairs (56%) more common than mutations at AT base pairs (44%). GC > AT was the most common type of base pair substitution (37%). The majority of the mutations at GC base pairs (78%) occurred at sites with G in the non-transcribed strand. All but one of eight mutations at CpG- sites were of the kind expected from deamination of methylated cytosine. Deletion of a single base pair (-1 frameshift) was three times more frequent than insertion of a single bp (+1 frameshift). Almost half (6/13) of the small (3-52 bp) deletions within the coding sequence clustered in the 5' end of exon 2. Short repeats and other sequence motifs that have been associated with replication error were found in the flanking regions of most of the frameshifts and small deletions. However, several differences in the local sequence context between +/-1 frameshift and deletion mutations were also noticed. The present results identify positions 197, 146 and possibly 131 as hotspots for base substitution mutations, and confirm previously reported hotspots at positions 197, 508 and 617. In addition, the earlier notion of a deletion hotspot in the 5'end of exon 2 was confirmed. The observations of these mutational cluster regions in different human populations suggest that they are due to endogeneous mechanisms of mutagenesis, or to ubiquitous environmental influences. The emerging background spectrum of somatic in vivo mutation in the human hprt gene provides a useful basis for comparisons with radiation or chemically induced mutational spectra, as well as with gene mutations in human tumors.      

Hemoglobin and albumin adducts of benzene oxide among workers exposed to high levels of benzene

Benzene oxide (BO) reacts with cysteinyl residues in hemoglobin (Hb) and albumin (Alb) to form protein adducts (BO-Hb and BO-Alb), which are presumed to be specific biomarkers of exposure to benzene. We analyzed BO-Hb in 43 exposed workers and 42 unexposed controls, and BO-Alb in a subsample consisting of 19 workers and 19 controls from Shanghai, China, as part of a larger cross-sectional study of benzene biomarkers. The adducts were analyzed by gas chromatography-mass spectrometry following reaction of the protein with trifluoroacetic anhydride and methanesulfonic acid. When subjects were divided into controls (n = 42) and workers exposed to < or =31 (n = 21) and >31 p.p.m. (n = 22) benzene, median BO-Hb levels were 32.0, 46.7 and 129 pmol/g globin, respectively (correlation with exposure: Spearman r = 0.67, P < 0.0001). To our knowledge, these results represent the first observation in humans that BO-Hb levels are significantly correlated with benzene exposure. Median BO-Alb levels in these 3 groups were 103 (n = 19), 351 (n = 7) and 2010 (n = 12) pmol/g Alb, respectively, also reflecting a significant correlation with exposure (Spearman r = 0.90, P < 0.0001). The blood dose of BO predicted from both Hb and Alb adducts was very similar. These results clearly affirm the use of both Hb and Alb adducts of BO as biomarkers of exposure to high levels of benzene. As part of our investigation of the background levels of BO-Hb and BO-Alb found in unexposed persons, we analyzed recombinant human Hb and Alb for BO adducts. Significant levels of both BO-Hb (19.7 pmol/g) and BO-Alb (41.9 pmol/g) were detected, suggesting that portions of the observed background adducts reflect an artifact of the assay, while other portions are indicative of either unknown exposures or endogenous production of adducts.      

Continuous infusion cisplatin and etoposide chemotherapy for cancer of unknown primary site (CUPS) in Taiwan, a region with a high prevalence of endemic viral infections

BACKGROUND: To evaluate the efficacy and toxicity of cisplatin/etoposide continuous infusion chemotherapy for cancer of unknown primary site in Taiwan, a region with a high prevalence of endemic viral infections. METHOD: Between April 1994 and February 1996, 20 patients with a diagnosis of CUPS were treated, including 15 males and five females, of average age 63.3 years (range 41-83 years). Continuous intravenous infusion of etoposide 80 mg/m2 and cisplatin 25 mg/m2 was given for 3 days every 3 weeks. Pretreatment tumor marker and viral serology studies were performed for baseline evaluation. Nearly two-thirds of the patients had poorly differentiated carcinoma. The average number of metastatic sites was 2.65 (range 1-4), with liver and lymph node involvement predominating. RESULTS: The overall response rate was 25% (95% CI 17.7-32.3%); 30.7% for poorly differentiated cancers and 25% for well differentiated cancers. Median survival was 4 months (range 1-12 months), 4.8 months for patients attaining partial response. Toxicity was moderate, grade 3 and 4 neutropenia occurred in 55% and grade 3 and 4 thrombocytopenia in 40%; other toxicities were mild. CA125 and CA199 were elevated in more than 50% of patients. Viral serology studies were not significantly different from those of the indigenous population. CONCLUSION: Etoposide and cisplatin combination chemotherapy has modest activity in patients with extensive CUPS and, at the schedule and dosage given, it is associated with moderate toxicity.      

Detection of microcystin synthetase genes in health food supplements containing the freshwater cyanobacterium Aphanizomenon flos-aquae.

In this study we investigated the presence of toxin-producing cyanobacterial contaminants in food supplements manufactured from blooms of the non-toxic freshwater cyanobacterium Aphanizomenon flos-aquae. Previous reports investigating the contamination of health food supplements with toxin-producing cyanobacteria have used chemical and or biochemical methods such as HPLC, ELISA and protein phosphatase assays. Whilst these studies have drawn attention to the presence of hepatotoxic microcystins in some commercially available food supplements, the methods used do not provide any information on the source of the contaminant. Such information would be useful for the quality control of food supplements produced for human consumption. In this study we applied a molecular technique, involving the amplification of the 16s rRNA gene, the phycocyanin operon, and two genes of the microcystin synthetase gene cluster to show that all 12 food supplement samples, sourced from various internet distributors and containing non-toxic A. flos-aquae, also contained toxigenic cyanobacteria. Sequencing of the microcystin synthetase genes detected in all of the food supplements showed that M. aeruginosa was the organism responsible for the production of microcystins in the samples. The presence of microcystins in the food supplements was confirmed by ELISA, with concentrations within the range of 0.1--4.72 microgg(-1) (microcystin-LR equivalents). Given that the molecular methods applied here are highly sensitive, and show good agreement with the results obtained from ELISA, we believe that they could potentially be used as a quality control technique for food products that contain cyanobacteria.     

Genetic Analysis of PARK2 and PINK1 Genes in Brazilian Patients with Early-Onset Parkinson's Disease

Parkinson''s disease is the second most frequent neurodegenerative disorder in the world, affecting 1-2% of individuals over the age of 65. The etiology of Parkinson''s disease is complex, with the involvement of gene-environment interactions. Although it is considered a disease of late manifestation, early-onset forms of parkinsonism contribute to 5–10% of all cases. In the present study, we screened mutations in coding regions of PARK2 and PINK1 genes in 136 unrelated Brazilian patients with early-onset Parkinson''s disease through automatic sequencing. We identified six missense variants in PARK2 gene: one known pathogenic mutation, two variants of uncertain role, and three nonpathogenic changes. No pathogenic mutation was identified in PINK1 gene, only benign polymorphisms. All putative pathogenic variants found in this study were in heterozygous state. Our data show that PARK2 point mutations are more common in Brazilian early-onset Parkinson''s disease patients (2.9%) than PINK1 missense variants (0%), corroborating other studies worldwide.     

An antigenic domain of the Leishmania amazonensis nucleoside triphosphate diphosphohydrolase (NTPDase 1) is associated with disease progression in susceptible infected mice

An antigenic conserved B domain was previously identified within nucleoside triphosphate diphosphohydrolases (NTPDases) of plants and parasites. Now, the r-potDomain B, a 6× His-tag polypeptide belonging to the conserved B domain from the potato apyrase, and synthetic peptides LbB1LJ and LbB2LJ derived from the B domain from Leishmania NTPDase 1 were used as molecular tools for studies of the Leishmania amazonensis NTPDase 1. Widespread subcellular location of the specific NTPDase 1 was detected by Western blots of promastigote fractions and ultrastructural immunocytochemical microscopy using immune sera raised against these biomolecules. In addition, the L. amazonensis-infected BALB/c mice were evaluated at 12 to 120 days after infection, which progresses showing typical nodular lesion. High antibody reactivity with either r-potDomain B, LbB1LJ, or LbB2LJ was found in L. amazonensis-infected BALB/c mice indicating the antigenicity of the B domain from NTPDase 1 isoform. The IgG1 antibody reactivity significantly increased at 90–120 days postinfection, 18- to 24-fold when compared to the 12th day, and remained elevated even at 120th after infection, coinciding with the most active stage of the disease. In contrast, significantly higher IgG2a antibody reactivity with each biomolecule was observed at 40th day, about two- to fourfold higher than those found at 12th or 20th day, and decreased along 120-day period. Apparently, the conserved B domain is capable to induce IgG2a production in early disease stages. All together, these results suggest that r-potDomain B or synthetic peptides could be molecular starting points in experimental protocols of immunotherapy and/or vaccination for leishmaniasis.     

Nasal endoscopic and CT scan alterations of the paranasal sinuses as predictors of severity in patients with cystic fibrosis

Cystic Fibrosis (CF) results from mutation in the transmembrane conductance regulator gene, responsible for controlling secretory processes. The upper airways (UA) are usually involved in the form of chronic pansinusitis.ObjectiveTo evaluate UA changes in patients with CF and to establish the correlations between sinonasal CT and endoscopic endonasal findings and disease severity.MethodCross-sectional and prospective study with 20 patients older than 5 years with CF, assessing the Shwachman-Kulczycki (S-K) score, paranasal sinus tomography (CT) (Lund-Mackay score) and nasal endoscopy (Meltzer score).ResultsCT scan alterations were observed in 94% of cases. Endoscopic alterations findings in the upper airways were found in 10 patients. Nasal polyps were found in 3 patients (15%). There was a correlation between the intensity of changes on the CT and S-K score (p = 0.0097), and between endoscopic findings and S-K score (p = 0.0318). There was a positive correlation between the presence of chronic colonization and endoscopic findings (p = 0.0325), which was not observed on the CT (p = 0.2941).ConclusionThere is an inverse correlation between the S-K clinical score and nasal endoscopy and CT findings. Therefore, patients who are clinically more severe according to the S-K score have greater UA involvement.