MutK may be a 32 kDa protein and be widespread among proteobacteria.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Biomedical subjects
D Moreira
Publications and source records attributed to D Moreira.
Intercomparison of calibration procedures for 192Ir HDR sources in Brazil.
The lack of well established dosimetry protocols for HDR sources is a point of great concern regarding the uniformity of procedures within a particular country and worldwide. The main objective of this paper is to report the results from ten institutions of an intercomparison of calibration procedures for 192Ir HDR sources currently in use in Brazil. The treatment irradiator of one institution was calibrated by a reference system and used by all participants with their own measuring electrometers and ionization chambers under the same experimental conditions. Two methods were used: the calibration jig and the well-type ionization chamber. Each participant was allowed to use their own method and formalism. The results of this exercise were very positive since this was the first time in Brazil that a group of users gathered to share their experience and openly discuss the physical concepts behind the calibration procedures. The results were all within +/-3.0%, except one case where -4.6% was observed and later identified as a problem with the Nk value for x-rays. Though the magnitude of the deviations found was generally acceptable considering the diversity of formalisms currently in use, a proposal is now being prepared to be adopted as a national protocol. The identification of the institutions was left out for the sake of confidentiality.
Brachytherapy↗
Unusually high evolutionary rate of the elongation factor 1 alpha genes from the Ciliophora and its impact on the phylogeny of eukaryotes.
The elongation factor 1 alpha (EF-1 alpha) has become widely employed as a phylogenetic marker for studying eukaryotic evolution. However, a disturbing problem, the artifactual polyphyly of ciliates, is always observed. It has been suggested that the addition of new sequences will help to circumvent this problem. Thus, we have determined 15 new ciliate EF-1 alpha sequences, providing for a more comprehensive taxonomic sampling of this phylum. These sequences have been analyzed together with a representation of eukaryotic sequences using distance-, parsimony-, and likelihood-based phylogenetic methods. Such analyses again failed to recover the monophyly of Ciliophora. A study of the substitution rate showed that ciliate EF-1 alpha genes exhibit a high evolutionary rate, produced in part by an increased number of variable positions. This acceleration could be related to alterations of the accessory functions acquired by this protein, likely to those involving interactions with the cytoskeleton, which is very modified in the Ciliophora. The high evolutionary rate of these sequences leads to an artificial basal emergence of some ciliates in the eukaryotic tree by effecting a long-branch attraction artifact that produces an asymmetric topology for the basal region of the tree. The use of a maximum-likelihood phylogenetic method (which is less sensitive to long-branch attraction) and the addition of sequences to break long branches allow retrieval of more symmetric topologies, which suggests that the asymmetric part of the tree is most likely artifactual. Therefore, the sole reliable part of the tree appears to correspond to the apical symmetric region. These kinds of observations suggest that the general eukaryotic evolution might have consisted of a massive radiation followed by an increase in the evolutionary rates of certain groups that emerge artificially as early branches in the asymmetric base of the tree. Ciliates in the case of the EF-1 alpha genes would offer clear evidence for this hypothesis.
Amino Acid Sequence↗
Efficient removal of PCR inhibitors using agarose-embedded DNA preparations.
The use of agarose blocks containing embedded DNA improves the PCR amplification from templates naturally contaminated with polysaccharides or humic acids, two powerful PCR inhibitors. Presumably, the difference in size between the DNA macromolecules and these contaminants allows their effective removal from the agarose blocks by diffusion during the washing steps, whereas genomic DNA remains trapped within them. In addition, agarose-embedded DNA can be directly used for PCR since low melting point agarose does not interfere with the reaction. This simple and inexpensive method is also convenient for genomic DNAs extracted by other procedures, and it is potentially useful for samples containing other kinds of soluble inhibitors, overcoming this important problem of current amplification techniques.
DNA↗
Symbiosis between methanogenic archaea and delta-proteobacteria as the origin of eukaryotes: the syntrophic hypothesis
We present a novel hypothesis for the origin of the eukaryotic cell, or eukaryogenesis, based on a metabolic symbiosis (syntrophy) between a methanogenic archaeon (methanobacterial-like) and a delta-proteobacterium (an ancestral sulfate-reducing myxobacterium). This syntrophic symbiosis was originally mediated by interspecies H2 transfer in anaerobic, possibly moderately thermophilic, environments. During eukaryogenesis, progressive cellular and genomic cointegration of both types of prokaryotic partners occurred. Initially, the establishment of permanent consortia, accompanied by extensive membrane development and close cell-cell interactions, led to a highly evolved symbiotic structure already endowed with some primitive eukaryotic features, such as a complex membrane system defining a protonuclear space (corresponding to the archaeal cytoplasm), and a protoplasmic region (derived from fusion of the surrounding bacterial cells). Simultaneously, bacterial-to-archaeal preferential gene transfer and eventual replacement took place. Bacterial genome extinction was thus accomplished by gradual transfer to the archaeal host, where genes adapted to a new genetic environment. Emerging eukaryotes would have inherited archaeal genome organization and dynamics and, consequently, most DNA-processing information systems. Conversely, primordial genes for social and developmental behavior would have been provided by the ancient myxobacterial symbiont. Metabolism would have been issued mainly from the versatile bacterial organotrophy, and progressively, methanogenesis was lost.
Journal Article↗
Genomic organization analysis of acidophilic chemolithotrophic bacteria using pulsed field gel electrophoretic techniques.
The genomic organization of acidophilic chemolithotrophic bacteria belonging to the genus Thiobacillus, Thiomonas and Leptospirillum was studied using pulsed field gel electrophoresis techniques (PFGE). The electrophoretic analysis of intact DNA prepared from different strains showed that all have a circular chromosome, with sizes ranging from 1.9 Mb for Leptospirillum ferrooxidans ATCC 49879, the smallest genome for an acidophilic strict chemolithoautotrophic microorganism, to 3.8 Mb for Thiomonas cuprina DSM 5495, the largest in this study. The number of extrachromosomal elements present varied from none, as observed in several isolates of Leptospirillum ferrooxidan, to five in Thiobacillus thiooxidans ATCC 8085. The mixotroph Thiomonas cuprina DSM 5495 was found to have a linear 50 kb megaplasmid which was inducible when the bacteria was grown in chemolithotrophic conditions. Low-frequency restriction fragment analysis (LFRFA) of different acidophilic chemolithotrophs and related species was carried out by PFGE to determine macrorestriction patterns for rare cutters (SpeI, XbaI, SwaI, PmeI), which were then used for taxonomic identification (karyotyping), genome size determination, and generation of physical and genetic maps.
Chromosome Mapping↗
Phylogeny of Thiobacillus cuprinus and other mixotrophic thiobacilli: proposal for Thiomonas gen. nov.
The complete 5S and 16S ribosomal DNA (rDNA) sequences of the facultatively chemolithotrophic bacterium Thiobacillus cuprinus and results of a comparison of these sequences with homologous sequences from several proteobacterial species supported affiliation of T. cuprinus with the beta 1 subgroup of the Proteobacteria. T. cuprinus, Thiobacillus intermedius, Thiobacillus perometabolis, and Thiobacillus thermosulfatus form a phylogenetic cluster that comprises some of the thiobacilli capable of mixotrophic growth. This cluster is related to some pseudomonads and Alcaligenes species belonging to the beta subclass. In addition, a low-frequency restriction fragment analysis (LFRFA) of some mixotrophic thiobacilli and some related species was carried out by using pulsed-field gel electrophoresis (PFGE) to determine the SpeI and XbaI macrorestriction patterns and genome sizes of these organisms. The correlation of the LFRFA results and the 16S rDNA analysis results and the usefulness of the two analyses are discussed. The PFGE fingerprints suggested that Thiobacillus sp. strain ATCC 27793 is related to T. intermedius rather than to T. perometabolis, as described previously. The distinctive characteristics of the mixotrophic species analyzed in this work, their phylogenetic relatedness, and their physiological differences from other groups belonging to the Proteobacteria, including other thiobacilli, suggest that these organisms should be transferred to a new genus, the genus Thiomonas gen. nov.
DNA, Bacterial↗
Efficient 5'-end labeling of oligonucleotides containing self-complementary sequences.
Explore the source record for details and available documents.
Bacteriophage T4↗
PCR-mediated detection of the chemolithotrophic bacterium Thiobacillus cuprinus using 23S rDNA- and 16S/23S intergenic spacer region-targeted oligonucleotide primers.
Bioleaching is carried out by chemolithotrophic microorganisms, most of them belonging to the genera Thiobacillus and Leptospirillum. The role of the mixotrophic species T. cuprinus in this process is controversial, since its ecological study applying classical detection techniques to natural or industrial environments is very difficult. For this reason, we have developed an alternative method based on PCR-mediated detection using specific oligonucleotide primers that target variable regions of the 23S rRNA coding gene and of the 16S/23S intergenic spacer region. Specificity and sensitivity of PCR amplifications performed with both kinds of primers were studied.
Base Sequence↗
[Catheter ablation of atrial tachyarrhythmias].
Explore the source record for details and available documents.
Adult↗
Assignment of genes to Leishmania infantum chromosomes: karyotype and ploidy.
The use of various pulsed-field electrophoresis methodologies under different conditions allowed us to determine the Leishmania infantum karyotype. A total of 25 chromosomal bands ranging in size from 375 to 3300 kb were resolved amounting to a minimum genomic DNA mass of about 2.6 x 10(7) pb. By molecular hybridization and on the basis of the karyotype, specific gene sequences could be assigned to particular chromosomes. A bias in the chromosomal distribution of different markers was found since 9 out of the 12 analysed gene markers hybridize with chromosomal bands XIXa and XIXb. We infer that chromosomal bands XIXa and XIXb, differing in about 30 kb, could be representing a pair of homologous chromosomes and that another pair of homologs may be also defined by chromosomal bands XVII and XVIII.
Animals↗
Intramural abscess of the duodenum resulting from perforated peptic ulcer.
Even in this age of effective medical treatment for peptic ulcers, their complications remain the same. Many require prompt surgical intervention. We present an unusual case of postbulbar duodenal ulcer complicated by intramural perforation and abscess formation. Such complications have a high mortality rate because of frequent delays in diagnosis and treatment caused by a lack of peritoneal signs or other specific clinical findings.
Abscess↗
Characterization of double potentials during ventricular tachycardia. Studies during transient entrainment.
BACKGROUND: Double potentials have been recorded during reentrant tachycardias in animal models. Although they have also been recorded during ventricular tachycardia in humans, their meaning is uncertain. METHODS AND RESULTS: We used transient entrainment as a method to help further understand the meaning of double potentials recorded during ventricular tachycardia in humans. Three patients with ventricular tachycardia (cycle lengths, 500, 450, and 290 msec) were studied. During transient entrainment of ventricular tachycardia (pacing cycle length, 470-260 msec), both double potential deflections were captured at the pacing cycle length. One deflection was captured with a short activation time, and the other deflection was captured with a long activation time. During ventricular pacing, the deflections were associated by the long rather than the short interdeflection interval. At termination of pacing, each double potential deflection was associated with separate but sequential QRS complexes, and each deflection maintained the same electrogram morphology at relatively "slow" overdrive pacing rates. The short interdeflection interval shortened further with faster pacing rates (to less than the ventricular refractory period), making it unlikely that both deflections of the double potential represent active depolarization of the same tissue. In two patients, at a critically rapid pacing rate, one of the double potential deflections changed morphology abruptly, associated with a shortened stimulus-to-double potential time interval (from 520 to 110 msec and from 530 to 240 msec, respectively), indicating a change in the direction of activation that caused that deflection. Interruption of ventricular tachycardia was associated with disappearance of the double potentials at the same recording site. The double potentials did not immediately bracket an area of slow conduction. CONCLUSIONS: These data suggest that double potentials recorded only during ventricular tachycardia represent activation wave fronts on either side of an area of block within a reentrant circuit. Thus, double potentials recorded during ventricular tachycardia in these patients do not appear to represent slow conduction per se but rather appear to represent an area of block at the center of a reentrant circuit around which the reentrant wave front circulates.
Aged↗
Diatrizoate meglumine-induced dilation of rat basilar artery: an in vitro study.
Explore the source record for details and available documents.
Animals↗
Candida spp. biotypes in the oral cavity of school children from different socioeconomic categories in Piracicaba-SP, Brazil.
Two hundred and thirty-nine (239) Brazilian children, distributed into five distinct socioeconomic categories (A to E) were studied. Saliva samples were analyzed as to flow rate, pH, buffer capacity and microbial parameters. The results revealed the presence of Candida spp. in 47.3% of the samples. The most commonly isolated species was C. albicans, in all socioeconomic categories, followed by C. tropicalis, C. krusei and C. parapsilosis. There was no statistical correlation between secretion rate, buffer capacity and Candida spp. CFU/ml. The prevalence of Candida spp. did not differ substantially among the groups; however the microorganisms were more detected in categories B and C. Among all species, C. albicans was the most prevalent. Only 5% of the sample presented more than one species--C. albicans associated with C. tropicalis, C. parapsilosis or C. krusei. It was possible to detect a significant correlation between caries indices and the socioeconomic categories. All categories presented increased caries indices; however the studied population was considered of low caries risk. There was no positive correlation between the presence of Candida and caries risk in the analyzed population.
Brazil↗
Salivary counts of mutans streptococci and lactobacilli in children ageing 6-8 year old having a socioeconomic background in Brazil.
Saliva samples from students aged 6 to 8 year-old were analysed in order to determine the incidence of Streptococcus group mutans and Lactobacillus. Two hundred children were examined, distributed in five socioeconomic categories (A to E). Stimulated saliva samples were collected and inoculated into the SB20 and Rogsa agar culture medium for the Streptococcus and Lactobacillus cultivation. After growth, the number of these microorganisms (CUF/mL) was determined after identification of the representative colonies by biochemical methods on the basis of carbohydrate fermentation. A significative part of the population, particularly among the lower socioeconomic categories (D/E) was considered a high risk group in developing dental caries because of the high number of Streptococcus group mutans and Lactobacillus.
Brazil↗