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Biomedical subjects

J Antón

Publications and source records attributed to J Antón.

15 recordsLinked to original sources
PubMed2001

Chromosome length polymorphism in Cryptococcus neoformans clinical and environmental isolates.

A protocol for intact DNA preparation from the basidiomycetous yeast Cryptococcus neoformans has been developed and applied to karyotyping C. neoformans isolates displaying different degrees of capsule formation. A total of 46 strains have been analyzed: 23 (50%) isolated from environmental samples (pigeon droppings), all of them belonging to C. neoformans var. neoformans; and 23 (50%) from clinical samples (human and veterinarian) including 10 isolates of C. neoformans var. neoformans and 13 isolates of C. neoformans var. gattii. Our results showed a global genome size ranging from 14.2 to 20.9 Mb for variety neoformans and from 7.9 to 16.8 Mb for variety gattii. The karyotype diversity was very high for variety neoformans (29 different patterns for the 33 analyzed strains) and lower for variety gattii (six different patterns for 13 strains). No grouping among variety neoformans strains from the same origin was found indicating very high genome diversity for this variety, irrespectively of the origin of the strains.

Journal Article↗
PubMed2000

Prokaryotic diversity in Zostera noltii-colonized marine sediments.

The diversity of microorganisms present in a sediment colonized by the phanerogam Zostera noltii has been analyzed. Microbial DNA was extracted and used for constructing two 16S rDNA clone libraries for Bacteria and Archaea. Bacterial diversity was very high in these samples, since 57 different sequences were found among the 60 clones analyzed. Eight major lineages of the Domain Bacteria were represented in the library. The most frequently retrieved bacterial group (36% of the clones) was delta-Proteobacteria related to sulfate-reducing bacteria. The second most abundant group (27%) was gamma-Proteobacteria, including five clones closely related to S-oxidizing endosymbionts. The archaeal clone library included members of Crenarchaeota and Euryarchaeota, with nine different sequences among the 15 analyzed clones, indicating less diversity when compared to the Bacteria organisms. None of these sequences was closely related to cultured Archaea organisms.

Archaea↗
PubMed2000

Extremely halophilic bacteria in crystallizer ponds from solar salterns.

It is generally assumed that hypersaline environments with sodium chloride concentrations close to saturation are dominated by halophilic members of the domain Archaea, while Bacteria are not considered to be relevant in this kind of environment. Here, we report the high abundance and growth of a new group of hitherto-uncultured Bacteria in crystallizer ponds (salinity, from 30 to 37%) from multipond solar salterns. In the present study, these Bacteria constituted from 5 to 25% of the total prokaryotic community and were affiliated with the Cytophaga-Flavobacterium-Bacteroides phylum. Growth was demonstrated in saturated NaCl. A provisional classification of this new bacterial group as "Candidatus Salinibacter gen. nov." is proposed. The perception that Archaea are the only ecologically relevant prokaryotes in hypersaline aquatic environments should be revised.

Bacteroides↗
PubMed2000

Pulsed-field gel electrophoresis analysis of virus assemblages present in a hypersaline environment.

A method for analyzing virus assemblages in aquatic environments was developed and used for studying the highest-salinity ponds (from 13.4 to 35% salinity) from a multi-pond solar saltern in Alicante, Spain. The protocol consisted of a series of concentration and purification steps including tangential flow filtration and ultracentrifugation, followed by the preparation of total viral nucleic acids that were subsequently separated by pulsed-field gel electrophoresis. For every sample analyzed, a characteristic DNA pattern was obtained, whose complexity was related to viral diversity. The comparison of our results with a similar analysis carried out with marine virus assemblages shows that, as expected, the viral diversity corresponding to the analyzed hypersaline environment is considerably lower than that of a marine environment.

Bacteriophages↗
PubMed1999

Structural studies on the acidic exopolysaccharide from Haloferax denitrificans ATCC 35960.

The structure of a linear, acidic exopolysaccharide isolated from the Archaeon Haloferax denitrificans ATCC 35960 has been determined using NMR spectroscopy. The sugar residues in the repeating unit of the polysaccharide were identified as Gal and GlcA2,3NAc after the assignment of the 1H and 13C resonances using COSY, HOHAHA, HMQC and HMQC-TOCSY experiments. The sequence of the residues in the polysaccharide was established from the inter-residue connectivities observed in the HMQC-NOESY plot. The only sugar released on acid hydrolysis was shown to be D-Gal by GLC analysis, while the absolute configuration of the acidic sugars was shown to be D by comparison of the carbon chemical shifts with those of model compounds. Partial acid hydrolysis yielded a tetrasaccharide, terminated by D-Gal at the reducing end, whose structure confirmed that of the repeating unit of the polysaccharide as-->4)-beta-D-GlcpA2,3NAc-(1-->4)-beta-D-GlcpA2, 3NAc-(1-->4)-alpha-D-GlcpA2,3NAc-(1-->3)-alpha-D-Galp- (1-->, where D-GlcpA2,3NAc is 2,3-diacetamido-2,3-dideoxy-D-glucopyranosiduronic acid.

Acids↗
PubMed1999

Fluorescence in situ hybridization analysis of the prokaryotic community inhabiting crystallizer ponds.

A fluorescence in situ hybridization (FISH) protocol suitable for the identification of prokaryotes inhabiting hypersaline environments was developed and applied to several crystallizer ponds with salinities above 36% from a multipond solar saltern in Alicante, Spain. Two morphotypes were abundant in these environments: rods and square or square-like prokaryotes that could be affiliated to Bacteria and Archaea, respectively, by FISH with domain-specific probes. FISH with a newly designed probe proved that the archaeal 16S rDNA sequence most frequently recovered from the crystallizers, SPhT, originated from the dominant square-like prokaryotes. These uncultured prokaryotes have the morphology of Walsby's square bacteria. Additionally, FISH with a probe targeted to the genus Haloarcula, members of which are frequently isolated from this environment, indicated that this genus accounts for less than 0.1% of the total prokaryotic community.

Archaea↗
PubMed1999

Diversity of free-living and attached bacteria in offshore Western Mediterranean waters as depicted by analysis of genes encoding 16S rRNA.

In a previous study (S. G. Acinas, F. Rodríguez-Valera, and C. Pedrós-Alió, FEMS Microbiol. Ecol. 24:27-40, 1997), community fingerprinting by 16S rDNA restriction analysis applied to Mediterranean offshore waters showed that the free-living pelagic bacterial community was very different from the bacterial cells aggregated or attached to particles of more than about 8 micrometer. Here we have studied both assemblages at three depths (5, 50, and 400 m) by cloning and sequencing the 16S rDNA obtained from the same samples, and we have also studied the samples by scanning electron microscopy to detect morphology patterns. As expected, the sequences retrieved from the assemblages were very different. The subsample of attached bacteria contained very little diversity, with close relatives of a well-known species of marine bacteria, Alteromonas macleodii, representing the vast majority of the clones at every depth. On the other hand, the free-living assemblage was highly diverse and varied with depth. At 400 m, close relatives of cultivated gamma Proteobacteria predominated, but as shown by other authors, near the surface most clones were related to phylotypes described only by sequence, in which the alpha Proteobacteria of the SAR11 cluster predominated. The new technique of rDNA internal spacer analysis has been utilized, confirming these results. Clones representative of the A. macleodii cluster have been completely sequenced, producing a picture that fits well with the idea that they could represent a genus with at least two species and with a characteristic depth distribution.

Bacteria↗
PubMed1999

Posttraumatic subgaleal hematoma: a case report and review of the literature.

INTRODUCTION: A subgaleal hematoma or subaponeurotic hemorrhage occurs infrequently and is usually seen in pediatric patients, especially in the neonatal period. It may be associated with coagulation disorders. CASE REPORT: We report on a previously healthy 19-month-old patient who presented with an extensive subgaleal hematoma and significant anemia secondary to a fall. DISCUSSION: A literature review was conducted, and the etiology, diagnosis, and treatment of the subgaleal hematoma are discussed. CONCLUSION: Conservative treatment, except in select severe cases, is recommended for this condition.

Accidental Falls↗
PubMed1998

The structure of the exocellular polysaccharide produced by the Archaeon Haloferax gibbonsii (ATCC 33959).

The structure of the neutral exocellular polysaccharide isolated from the Archaeon Haloferax gibbonsii (ATCC 33959) has been determined using acid hydrolysis, methylation analysis and NMR spectroscopy. The polysaccharide contained D-Man, D-Glc, D-Gal and L-Rha in the ratios 2:1:3:1. The substitution patterns of the sugar residues were deduced from the methylation analysis which indicated the polymer to be composed of a heptasaccharide repeating unit containing two branches. The 1H and 13C NMR resonances of the component sugars were assigned using COSY, HOHAHA, HMQC, and HMQC-TOCSY 2D NMR experiments and the sequence of the sugars in the repeating unit was determined from NOESY and HMBC experiments. The structure can be written as: [formula: see text]

Carbohydrate Conformation↗
PubMed1998

Influence of diagnostic and treatment factors in the population pharmacokinetics of gentamicin.

Using the NONMEM program, the population kinetics of gentamicin were retrospectively studied in a series of 51 patients with different pathologies undergoing treatment (single or three daily doses) with gentamicin whose serum gentamicin levels were being monitored. Renal function, the type of treatment and cancer proved to be the covariates which affected drug clearance, while patient weight was found to govern the distribution volume. The distribution coefficient of gentamicin in the patients was 0.37 litres/kg, justifying gentamicin doses higher than those used conventionally. The optimized population model allowed us to simulate drug serum levels at 8 and 12h, as well as the area under the curve of gentamicin and its variability in patients with high distribution volumes when dosage regimens based on a single daily dose administration are implemented.

Abscess↗
PubMed1994

Halobacterial megaplasmids are negatively supercoiled.

Several covalently closed circular halobacterial megaplasmids (up to more than 500 kb) from different strains of Haloferax mediterranei, have been resolved by orthogonal-field alternating gel electrophoresis (OFAGE). These molecules seem to be negatively supercoiled in vivo, as deduced from the effect of intercalating agents affecting their topology and, therefore, their electrophoretic mobility. It has also been demonstrated that the topoisomerase II inhibitor novobiocin affects the native topological state of halobacterial megaplasmids impeding their migration in OFAGE under standard conditions for resolution of large supercoiled molecules.

DNA, Superhelical↗
PubMed1988

Production of an Extracellular Polysaccharide by Haloferax mediterranei.

The extremely halophilic archaebacterium Haloferax mediterranei produces an exocellular polymeric substance that gives the colonies a typical mucous character and is responsible for the appearance of a superficial layer in unshaken liquid medium. This exocellular polymeric substance can be obtained from the supernatant of shaken liquid cultures by cold ethanol precipitation, and yields as high as 3 mg/ml have been detected. The substance was produced under all the conditions tested and with all substrates assayed, although higher yields were obtained with sugars, particularly glucose, as carbon and energy source. The total exocellular polymeric substance produced was proportional to the total biomass. The polymer is a heteropolysaccharide containing mannose as the major component. Glucose, galactose, and another unidentified sugar were also present, as well as amino sugars, uronic acids, and a considerable amount of sulfate, which accounts for the acidic nature of the polymer. The infrared spectrum and specific assays showed the absence of acyl groups. The rheological properties of polymer solutions were studied, showing a pseudoplastic behavior and a high apparent viscosity at relatively low concentrations. Viscosity was remarkably resistant to extremes of pH, temperature, or salinity. These characteristics make this polymer interesting for enhanced oil recovery and other applications for which a very resistant thickening agent is required.

Journal Article↗
PubMedDate not supplied

[Allergic rhinitis and bronchial hyperreactivity].

BACKGROUND: Bronchial hyperreactivity (BHR) is a characteristic of bronchial asthma. Patients with allergic rhinitis who do not report symptoms of bronchial asthma on spirometry show BHR, which could indicate the presence of subclinical inflammation of the lower respiratory airway. The aim of this study was to investigate whether the patients diagnosed with allergic rhinitis in our unit without symptoms of bronchial asthma had bronchial hyperreactivity and to determine which allergens caused these symptoms in our patients. METHODS AND RESULTS: We performed a retrospective, observational study of patients diagnosed with allergic rhinitis in our Allergy Unit between August 2000 and December 2001. The patients' medical records were reviewed and data on the following were gathered: demographic information, age, sex, rhinitis symptoms (perennial or seasonal), conjunctivitis, atopic dermatitis, bronchitis, sensitization (specific IgE, skin tests, nasal challenge tests), total IgE levels, spirometry performed through stress test (positive with a decrease of FEV1 > 15 % with stress or an increase of FEV1 of 12 % after bronchodilation) and family history of allergic disease. A total of 135 medical records of patients with allergic rhinitis were reviewed. Of these, 68 did not report symptoms of bronchial asthma (35 men and 33 women aged between 4 and 18 years). Most of our patients (50/68) reported perennial asthma and were sensitized to mites (44/68). In 14/68 spirometry was not performed at diagnosis. Stress test was positive in 13/54 (24 %). All patients who showed bronchial hyperreactivity were sensitized to mites and only one of these reported seasonal rhinitis. CONCLUSIONS: According to the latest guidelines on the treatment and control of allergic rhinitis --The Allergic Rhinitis and its Impact on Asthma Workshop Report-- bronchial asthma and allergic rhinitis are distinct manifestations of a single airway and of the same disease. In view of our results, we recommend systematic evaluation of bronchial hyperreactivity in the study protocol of allergic rhinitis in patients who do not report symptoms of bronchial asthma.

Adolescent↗