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Biomedical subjects

M A Rodríguez

Publications and source records attributed to M A Rodríguez.

At least 19 recordsLinked to original sources
PubMed2006

Cyclosporine A from a nonpathogenic Fusarium oxysporum suppressing Sclerotinia sclerotiorum.

AIMS: To evaluate the antagonistic activity of Fusarium oxysporum nonpathogenic fungal strain S6 against the phytopathogenic fungus Sclerotinia sclerotiorum and to identify the antifungal compounds involved. METHODS AND RESULTS: The antagonistic activity of Fusarium oxysporum strain S6 was determined in vitro by dual cultures. The metabolite responsible for the activity was isolated by chromatographic techniques, purified and identified by spectroscopic methods as cyclosporine A. The antifungal activity against the pathogen was correlated with the presence of this metabolite by a dilution assay and then quantified. Cyclosporine A caused both growth inhibition and suppression of sclerotia formation. In a greenhouse assay, a significant increase in the number of surviving soybean (Glycine max) plants was observed when S. sclerotiorum and F. oxysporum (S6) were inoculated together when compared with plants inoculated with S. sclerotiorum alone. CONCLUSION: Fusarium oxysporum (S6) may be a good fungal biological control agent for S. sclerotiorum and cyclosporine A is the responsible metabolite involved in its antagonistic activity in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Cyclosporine A has not been previously described as an inhibitor of S. sclerotiorum. Its minimum inhibitory concentration (MIC) of 0.1 microg disc(-1) makes it suitable to use as a biofungicide. In vivo experiments showed that F. oxysporum (S6) is a good candidate for the biocontrol of S. sclerotiorum in soybean.

Antifungal Agents↗
PubMed2006

Learning by operant conditioning as a nonlinear self-organized process.

Responses of individuals have been rewarded in fixed ratio operant conditioning experiments throughout the last 5 years. The long numerical series of performance rates so obtained have been analyzed by using Fourier spectra, obtaining 1/f noise, and wavelet techniques for the analysis of local variability. These techniques reveal that the evolution of data in each individual is nonlinear but it fluctuates showing self-organized patterns in successive time scales, which leads to a long term logarithmic growth. Based on these observations a model has been developed. It can simulate with a great accuracy the rate of response exhibited by our subjects in all time scales.

Conditioning, Operant↗
PubMed2005

Anomalous roughening of viscous fluid fronts in spontaneous imbibition.

We report experiments on spontaneous imbibition of a viscous fluid by a model porous medium in the absence of gravity. The average position of the interface satisfies Washburn's law. Scaling of the interface fluctuations suggests a dynamic exponent z approximately 3, indicative of global dynamics driven by capillary forces. The complete set of exponents clearly shows that interfaces are not self-affine, exhibiting distinct local and global scaling, both for time (beta = 0.64 +/- 0.02, beta(*) = 0.33 +/- 0.03) and space (alpha = 1.94 +/- 0.20, alpha(loc) = 0.94 +/- 0.10). These values are compatible with an intrinsic anomalous scaling scenario.

Journal Article↗
PubMed2005

Clifford algebra approach to the coincidence problem for planar lattices.

The problem of coincidences of planar lattices is analyzed using Clifford algebra. It is shown that an arbitrary coincidence isometry can be decomposed as a product of coincidence reflections and this allows planar coincidence lattices to be characterized algebraically. The cases of square, rectangular and rhombic lattices are worked out in detail. One of the aims of this work is to show the potential usefulness of Clifford algebra in crystallography. The power of Clifford algebra for expressing geometric ideas is exploited here and the procedure presented can be generalized to higher dimensions.

Journal Article↗
PubMed2004

Ultrasonic flaw detection in NDE of highly scattering materials using wavelet and Wigner-Ville transform processing.

In ultrasonic non-destructive evaluation of highly scattering materials the backscattering noise may attain peak values greater than the searched flaw pulse and the mean value of noise spectrum is very similar to the searched echo spectrum. Several specific methods have been proposed for the reduction of this type of noise, but the comparison of the performance of different methods is still an open problem. In this paper, we make a comparison among some methods based on simultaneous representations in time and frequency/scale domains of the ultrasonic traces. Synthetic and experimental traces are de-noised using a discrete wavelet processor with decomposition level-dependent threshold selection and a method that combines Wigner-Ville transform and filtering in the time-frequency domain. The results are comparatively evaluated in terms of signal to noise ratio and probability of detection.

Journal Article↗
PubMed2004

Histopathology of Sclerotinia sclerotiorum attack on flower parts of Helianthus annuus heads in tolerant and susceptible varieties.

Sunflower head rot is a major disease caused by Sclerotinia sclerotiorum. Sunflower varieties which are tolerant to the fungus have been developed. The changes occurring in flower parts at different times after inoculation with pathogen ascospores were studied for two sunflower varieties (tolerant HA 302 and susceptible HA 89). In variety HA 302 there was cell collapse, changes in cell wall composition, and an increase in phenolic compounds in the tissues of corolla and style, which prevented the pathogen from advancing. This response was weaker in susceptible variety HA 89, and occurred only in the style, so did not stop the pathogen from developing and reaching the ovary. Phenolic compounds were found in HA 302 corolla and style tissues only when the pathogen was present, constituted an induced response that prevented further development of the fungus. Principal component analysis (PCA) showed that at the beginning of the infection there was no difference in behavior between the two varieties. The difference arose during the final observation times, when in variety HA 89, the pathogen colonized ovary, style and base of filaments and produced noticeable colonization of the corolla.

Argentina↗
PubMed2004

Rapid detection of cows' milk in sheeps' and goats' milk by a species-specific polymerase chain reaction technique.

A polymerase chain reaction (PCR) assay was developed for the specific identification of cows' milk in sheep's and goats' milk by using primers targeting the mitochondrial 12S rRNA gene. The use of a forward primer complementary to a conserved DNA sequence, along with a reverse primer specific for cow, yielded a 223-bp fragment from cows' milk DNA, whereas no amplification signal was obtained in sheep's and goats' milk DNA. The technique was applied to raw, pasteurized, and sterilized milk binary mixtures of cow-sheep and cow-goat, enabling the specific detection of cows' milk with a good sensitivity threshold (0.1%). The proposed PCR assay represents a rapid and straightforward method applicable to the authentication of milk and other dairy products in routine analysis.

Animals↗
PubMed2003

Optimisation of a solid-phase microextraction procedure for the determination of triazines in water with gas chromatography-mass spectrometry detection.

A procedure based on solid-phase microextraction (SPME) and gas chromatography-mass spectrometry, operating in the chemical ionisation mode, was developed and optimised in order to determine 10 triazines in water samples. Five different SPME fibers available for analysis [polydimethylsiloxane (PDMS) 100 microm, polyacrylate (PA) 80 microm, PDMS-divinylbenzene (DVB) 65 microm, Carbowax (CW)-DVB 65 microm, and Carboxen (CAR)-PDMS 75 microm] were tested, and PDMS-DVB was selected. To enhance the sensitivity of the SPME, variables affecting adsorption and desorption steps such as temperature, time, pH and ionic strength of the solution were optimised. Detection limits obtained were ranged between 2 and 17 ng l(-1), and precision values were below 8% for the selected PDMS-DVB fiber. The optimised method was applied to real water samples and no triazines were detected.

Gas Chromatography-Mass Spectrometry↗
PubMed2003

Ehp53, an Entamoeba histolytica protein, ancestor of the mammalian tumour suppressor p53.

This paper reports the identification of Ehp53, a p53-like Entamoeba histolytica protein, which binds to the human p53 DNA consensus sequence (oli-p53). Monoclonal antibodies against p53 (Ab-1 and Ab-2) recognized a single 53 kDa spot in two-dimensional gels and inhibited the formation of complexes produced by E. histolytica nuclear extracts and oli-p53. Additionally, E. histolytica gene promoter sequences with high homology to oli-p53 formed complexes with nuclear proteins that were abolished by oli-p53. Ehp53 protein levels increased in UV-irradiated trophozoites. This protein was also detected in Entamoeba moshkovskii and Entamoeba invadens. By confocal microscopy, Ehp53 was located in the nuclei, EhkO organelles and cytoplasm. The Ehp53-encoding gene was cloned and its predicted amino acid sequence showed 30-54 % and 50-57 % homology with important domains of the human and the Drosophila melanogaster p53 proteins, respectively. This homology included the tetramerization domain, the nuclear export signal and a nuclear localization signal. Ehp53 also contains seven of the eight DNA-binding residues and two of the four Zn(2+)-binding sites described for p53. A recombinant Ehp53 was recognized by Ab-2. Ehp53 is believed to be the first p53-like protein found in protozoa and may be the evolutionary ancestor of the mammalian p53.

Amino Acid Sequence↗
PubMed2002

Entamoeba histolytica: DNA carrier vesicles in nuclei and kinetoplast-like organelles (EhkOs).

Entamoeba histolytica, the protozoan responsible for human amoebiasis, has a complex genome, whose linear chromosomes and DNA circles have so far eluded detailed analysis. We report the detection by transmission electron microscopy of nuclear vesicles (0.05-0.3 microm in diameter) carrying DNA in E. histolytica trophozoites. In late anaphase many of these nuclear vesicles were found to be organized in structures of approximately 2.5 x 1 microm, in association with chromosomes and microtubules. In glutaraldehyde-fixed and detergent-treated trophozoites, nuclear vesicles displayed a non-membranous envelope. Binding of phosphotungstate stain and recognition by serum from patients with systemic lupus erythematosus indicated that these vesicles contain DNA. Similar DNA carrier vesicles were found in the cytoplasm and in the E. histolytica kinetoplast-like organelle (EhkO). By Feulgen staining, we detected DNA carrier vesicles entering or leaving the nuclei, suggesting a structural relationship between the nuclear vesicles and the vesicles present in the EhkOs.

Animals↗
PubMed2002

Anomalous roughening of Hele-Shaw flows with quenched disorder.

The kinetic roughening of a stable oil-air interface moving in a Hele-Shaw cell that contains a quenched columnar disorder (tracks) has been studied. A capillary effect is responsible for the dynamic evolution of the resulting rough interface, which exhibits anomalous scaling. The three independent exponents needed to characterize the anomalous scaling are determined experimentally. The anomalous scaling is explained in terms of the initial acceleration and subsequent deceleration of the interface tips in the tracks coupled by mass conservation. A phenomenological model that reproduces the measured global and local exponents is introduced.

Journal Article↗
PubMed2002

Two new HLA class I alleles recognised by PCR sequence-specific primer and sequencing based typing: B*3805 and Cw*0408.

Two new HLA class I alleles have been recognised by molecular-based typing. B*3805 was initially identified by polymerase chain reaction using sequence-specific primers (PCR-SSP) and afterwards confirmed by sequencing based typing (SBT) studies in a Spanish Caucasian blood cord unit. A unique nucleotide change throughout exons 2, 3 and 4, leading to the amino acid replacement Ser11Ala, differentiates B*3801 and *3805. This position behaves as a dimorphic residue in HLA-B and -C loci, and seems to be structurally unrelated to peptide and TcR recognition. Cw*0408 was first detected by SBT in two African American bone marrow donors in combination with its most structurally related allele, Cw*04011. The single amino acid change found between Cw*04011 and Cw*0408 was Thr163Leu, a residue involved in pocket A of the peptide-binding cleft. This new allele could be the result of a gene conversion event between Cw*04011 and any of the Cw*03 alleles.

Alleles↗
PubMed2002

[Right primary iliac artery rupture during transurethral resection of bladder tumor].

Injury to a large-caliber artery transurethral resection of a bladder tumor is a rare but serious complication. It is important that an anesthesiologist be able to detect such an injury, in order to include it among the many differential etiological diagnoses for shock. A 75-years-old man reported hematuria. An ultrasound image of the bladder showed many neoformations consistent with a diagnosis of multiple bladder neoplasms, and transurethral endoscopy was performed under subarachnoid anesthesia. Acute hypotension, bradycardia and shock developed 30 minutes into the procedure. The diagnosis was hypovolemic shock due to acute intraoperative hemorrhage, and exploratory laparotomy revealed an opening in the common iliac artery. The rupture was sutured. In spite of administration of crystalloids, colloids, blood products and vasoactive agents, a second operation was required due to hemodynamic instability. The patient died in the intensive care unit.

Aged↗
PubMed2002

[Results of C1-C2 transarticular screw fixation in a series of 20 patients].

OBJECTIVE: C1-C2 transarticular fixation is an increasingly used surgical method of treating atlantoaxial instability. When properly performed, it can safely provide fusion rates near 100%, but techniques of fixation in this region allow only a small margin of error. We here report the results of C1-C2 transarticular fixation in a series of 20 patients in which different procedures were selected according to the presenting disorder in each case. METHODS: The study group included 9 men and 11 women with a mean age of 48 years (range 17 to 68 years). The causes of instabilities were rheumatoid arthritis in nine patients, type II and III Hangman's fracture of traumatic origin in nine (in association with other lesions in three cases), pseudoarthrosis after type II odontoid fracture in one, and type III complex C1 fracture in a patient with ankylosing spondylitis. Preoperative assessment included flexion and extension plain radiographs and computed tomography (CT) and magnetic resonance imaging (MRI) scans. Operations included transarticular screw fixation in all cases; in patients with rheumatoid arthritis it was associated with sublaminar fixation and bone grafting following Sonntag's technique in all but two cases. Postoperative results were evaluated in relation to the biomechanical stability and fusion was studied by flexion and extension radiographs and CT scans. Pain relief in patients with rheumatoid arthritis patients was assessed using a 0-10 visual analogic scale (V.A.S.). RESULTS: In the traumatic group, a consolidation of the fracture and radiologic stability was achieved in all cases. In patients with rheumatoid arthritis, pain improved in all but not the neurological deficit, and in all cases a C1-C2 biomechanical stability was reached despite interlaminar graft resorption in two (25%) cases. With respect to complications, a lesion of the vertebral artery occurred in one case, deviation of the screw in two cases, and breakage of the screw without clinical repercussion in two other cases. CONCLUSION: C1-C2 transarticular screw fixation was a useful technique to achieve satisfacory biomechanical stability in patients with atlatoaxial instability of both inflammatory and traumatic origin with a low rate of complications.

Adolescent↗
PubMed2001

N-Cyclopropylimine-1-pyrroline rearrangement. A novel photochemical reaction.

[reaction: see text] A novel aza-(vinylcyclopropane-cyclopentene) photochemical rearrangement is reported. 1-Pyrrolines are easily synthesized in good yields from N-cyclopropylimines. Hydrogen, alkyl, and aryl groups can be placed anywhere within the system, and the reaction proceeds regiospecifically.

Journal Article↗
PubMed2001

Interface depinning in the absence of an external driving force.

We study the pinning-depinning phase transition of interfaces in the quenched Kardar-Parisi-Zhang model as the external driving force F goes towards zero. For a fixed value of the driving force, we induce depinning by increasing the nonlinear term coefficient lambda, which is related to lateral growth, up to a critical threshold. We focus on the case in which there is no external force applied (F=0) and find that, contrary to a simple scaling prediction, there is a finite value of lambda that makes the interface to become depinned. The critical exponents at the transition are consistent with directed percolation depinning.

Journal Article↗