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Biomedical subjects

P Cruz

Publications and source records attributed to P Cruz.

At least 19 recordsLinked to original sources
PubMed2005

Influence of the sediment on lead speciation in the Tagus estuary.

The aim of this work is to study the influence of the Tagus estuarine sediment on lead speciation in the overlying natural water. The water sample in the presence of the sediment was contaminated three times with Pb(II) in a laboratory experiment. In different periods of time, at 1-7 days after each contamination, small volumes of water were titrated with lead. The titration was followed by anodic stripping voltammetry in differential pulse mode. Before and after contamination systematic analysis of the voltammetric parameters (peak current, peak potential and peak width) were carried out to get a clear picture of Pb(II) complexation in the soluble fraction in contact with the sediment. Two main types of organic ligands, macromolecular ligands and small compounds, were detected before contamination. Both of them form labile complexes (degree of lability within the timescale of some milliseconds). The small compounds, with a diffusion coefficient similar to that of the free metal ion, present a homogeneous behaviour in terms of Pb complexation. On the other hand macromolecular ligands, with a diffusion coefficient of 1.2 x 10(-6) cm2s(-1), can be described by two different binding groups, which might be of phenolic and carboxylic type as presented by humic matter. The sediment eliminated lead contamination (10(-6) moldm(-3) was the maximum concentration added) from 12 dm3 of water (surface of 8 dm2) within 2 days. It was also found that the sediment released organic ligands responsible for both labile and inert Pb complexes "seen" by voltammetry. The release of organic ligands that decreases the bioavailability of Pb(II) was clearly detected 1 week after contamination. Therefore, the sediment acts as a buffer for lead through two mechanisms against lead contamination: removing lead ions from the solution and releasing organic ligands to the water column. In a short period of time the sediment responds as a self-cleaning system for Pb(II) contamination in the estuarine water, which may have a very important influence in environmental pollution.

Diffusion↗
PubMed2004

Population genetic structure of Pacific white shrimp (Litopenaeus vannamei) from Mexico to Panama: microsatellite DNA variation.

Genetic variation and population structure of wild white shrimp (Litopenaeus vannamei) from 4 geographic locations from Mexico to Panama were investigated using 5 microsatellite DNA loci. The genetic diversity between populations was indicated by the mean number of alleles per locus and mean observed heterozygosity, which ranged from 7.4 to 8.6 and from 0.241 to 0.388, respectively. Significant departures from Hardy-Weinberg equilibrium were found at most locations at each locus, with the exception Guatemala at Pvan0013, and were caused by high heterozygote deficiencies. Genetic differences between localities were detected by pairwise comparison based on allelic and genotypic frequencies, with the exception of locus Pvan1003. Significant pairwise F (ST) values between locations and total F (ST) showed that the white shrimp population is structured into subpopulations. However, population differentiation does not follow an isolation-by-distance model. Knowledge of the genetic diversity and structure of L.vannamei populations will be of interest for aquaculture and fisheries management to utilize and preserve aquatic biodiversity.

Animals↗
PubMed2002

[Metamizol versus propacetamol: comparative study of the hemodynamic and antipyretic effects in critically ill patients].

OBJECTIVE: To compare the antipyretic and hemodynamic effects of metamizol and propacetamol in critically ill patients with fever. PATIENTS AND METHODS: A prospective randomized trial enrolling 60 patients admitted to our postoperative intensive care unit with fever > 38 degrees C. Patients were assigned to group M to receive intravenous doses of 2 g of metamizol or group P to receive 2 g of propacetamol. Measures were central temperature (Ta), systolic (SBP), diastolic (DBP) and mean (MBP) blood pressures, mean pulmonary artery pressure, central venous pressure, pulmonary capillary pressure, pulmonary and systemic vascular resistance index, and mixed venous saturation. All measures were taken at four times: baseline and 30, 60 and 120 minutes after infusion of the medication. Patients whose SBP fell below 90 mm Hg were withdrawn from the study. RESULTS: Patient characteristics and baseline hemodynamics and Ta were similar in the two groups. We observed a significant decrease in temperature in both groups, the maximum decrease occurring 120 minutes after administration of the antipyretic (0.5 degree C and 0.6 degree in the metamizol and propacetamol groups, respectively). SBP, DBP, MBP, and the vascular resistance index decreased from baseline values in both groups 30, 60 and 120 minutes after dosing. Thirteen percent of the patients in group M and 6.67% in group P were withdrawn from the study because of hypotension. We observed no statistically significant differences between the groups in Ta or hemodynamic variables at any of the four moments of measurement. CONCLUSION: Both metamizol and propacetamol are effective antipyretics at the doses tested. However, both have adverse hemodynamic side effects that may be poorly tolerated by critically patients.

Acetaminophen↗
PubMed1998

Prevalence of intestinal encephalitozoonosis in Mexico.

Infections with Encephalitozoon (phylum Microspora) protozoa in immunodeficient patients have emerged worldwide. The prevalence of infections due to Encephalitozoon species in nonclinical populations remains unclear. We conducted a cross-sectional survey of two rural highland villages in Mexico by using monoclonal antibody 3B6 to Encephalitozoon in immunofluorescence to assess the prevalence of Encephalitozoon spores in human stools. We found that 20 (7.84%) of the 255 subjects were positive and that 15 (21.4%) of the 70 households had at least one member who was positive. These results suggest that Encephalitozoon species, most likely Encephalitozoon intestinalis, may be commonly present in community settings.

Animals↗
PubMed1997

The secondary structure of a fourteen-nucleotide fragment of the hairpin ribozyme.

A fourteen nucleotide RNA has been synthesized and its secondary structure investigated by non-denaturing polyacrylamide gel electrophoresis and 1H nuclear magnetic resonance spectroscopy. This fourteen nucleotide RNA corresponds to the hairpin loop end of the proposed secondary structure of the (-)sTRSV hairpin ribozyme. Non-denaturing polyacrylamide gel electrophoresis indicates that the fourteen nucleotide RNA exists predominantly as a monomer at a 1 mM strand concentration. Four peaks are found in the imino hydrogen region of the 1H NMR spectrum of the fourteen nucleotide RNA at this concentration. One-dimensional nuclear Overhauser effect spectroscopy of the imino hydrogen region of the 1H NMR spectrum gives results consistent with a model of the secondary structure of the fourteen nucleotide RNA having a three nucleotide hairpin loop and two double-stranded stems separated by a single bulged adenosine.

Base Composition↗
PubMed1994

[Oculomotor paralysis. The perspective of a neuro-ophthalmology consultation].

Ocular paresis is a usual diagnosis in neuro-ophthalmologic consultation, and its aetiology is indeed a challenge. The authors studied 3400 records concerning this consultation, between 1982 and the third quarter of 1993. During this period 221 cases with ocular paresis were selected. During this retrospective study we point out the following items: the cranial nerve affected; the neuro-ophthalmologic semiology; the aetiology and clinical evolution, according to the age groups. From 221 cases selected, 111 were paresis from the VIth pair (50.2%), 88 from the IIIrd pair (39.8%), 14 multiple paresis (6.4%) and 8 paresis from the IVth pair (3.6%). The most frequent complaint was diplopia (> 90%). As far as the aetiological diagnosis is concerned, this was easier to establish in patients > 50 years of age. In this age group the most usual aetiology was vascular and traumatic pathologies. In younger patients the most frequent pathologies were traumatic and tumoral. The prognostic was better in the vascular group, the paresis recovery being > 50% in all other pathologies, except the tumoral one.

Adolescent↗
PubMed1991

Relationship between total magnesium concentration and free intracellular magnesium in sheep red blood cells.

The cellular free magnesium concentration of ionophore A23187 permeabilized high potassium sheep erythrocytes was measured by 31P nuclear magnetic resonance spectroscopy, and the total cellular magnesium concentration was determined by atomic absorption spectroscopy. The free versus total cellular magnesium concentrations yield a linear relationship on a log-log scale in the concentration range from 0.3 to 1.92 mmol Mg/liter cells. Thus, free intracellular magnesium concentrations can be calculated from atomic absorption data. The method permits the estimation of physiologically or experimentally induced variations of intracellular free magnesium concentrations between 7 and 405 microM magnesium in cell water. This range encompasses the free magnesium concentration of 335 +/- 60 microM in cell water determined for untreated erythrocytes.

Adenosine Triphosphate↗
PubMed1990

'Hairpin' catalytic RNA model: evidence for helices and sequence requirement for substrate RNA.

We have identified the catalytic domain within the sequence of the negative strand of the satellite RNA of tobacco ringspot virus. Minimum energy RNA folding calculations predict a two dimensional model with four major helical regions which are supported by mutagenesis experiments. This model for the catalytic complex consists of a 50 base catalytic RNA and a 14 base substrate RNA folded together in a type of hairpin two dimensional structure. Part of the recognition region between the catalyst and substrate is two helices of 6 bases and 4 bases respectively. Catalytic activity remains when the bases in these two helices are changed but base pairing is maintained. Thus an appropriately engineered 'hairpin' catalyst is capable of cleaving heterologous RNA.

Base Sequence↗
PubMed1987

Raman spectroscopic study of left-handed Z-RNA.

The solvent conditions that induce the formation of a left-handed Z form of poly[r(G-C)] have been extended to include 6.5 M NaBr at 35 degrees C and 3.8 M MgCl2 at room temperature. The analysis of the A----Z transition in RNA by circular dichroism (CD), 1H and 31P NMR, and Raman spectroscopy shows that two distinct forms of left-handed RNA exist. The ZR-RNA structure forms in high concentrations of NaBr and NaClO4 and exhibits a unique CD signature. ZD-RNA is found in concentrated MgCl2 and has a CD signature similar to the Z form of poly[d(G-C)]. The loss of Raman intensity of the 813-cm-1 A-form marker band in both the A----ZR-RNA and A----ZD-RNA transitions parallels the loss of intensity at 835 cm-1 in the B----Z transition of DNA. A guanine vibration that is sensitive to the glycosyl torsion angle shifts from 671 cm-1 in A-RNA to 641 cm-1 in both ZD- and ZR-RNA, similar to the B----Z transition in DNA in which this band shifts from 682 to 625 cm-1. Significant differences in the glycosyl angle and sugar pucker between Z-DNA and Z-RNA are suggested by the 16-cm-1 difference in the position of this band. The Raman evidence for structural difference between ZD- and ZR-RNA comes from two groups of bands: First, Raman intensities between 1180 and 1600 cm-1 of ZD-RNA differ from those for ZR-RNA, corroborating the CD evidence for differences in base-stacking geometry. Second, the phosphodiester stretching bands near 815 cm-1 provide evidence of differences in backbone geometry between ZD- and ZR-RNA.

Circular Dichroism↗
PubMed1987

Structure, dynamics, and thermodynamics of mismatched DNA oligonucleotide duplexes d(CCCAGGG)2 and d(CCCTGGG)2.

The structures and hydrogen exchange properties of the mismatched DNA oligonucleotide duplexes d(CCCAGGG)2 and d(CCCTGGG)2 have been studied by high-resolution nuclear magnetic resonance. Both the adenine-adenine and thymine-thymine mismatches are intercalated in the duplexes. The structures of these self-complementary duplexes are symmetric, with the two strands in equivalent positions. The evidence indicates that these mismatches are not stably hydrogen bonded. The mismatched bases in both duplexes are in the anti conformation. The mismatched thymine nucleotide in d(CCCTGGG)2 is intercalated in the duplex with very little distortion of the bases or sugar-phosphate backbone. In contrast, the bases of the adenine-adenine mismatch in d(CCCAGGG)2 must tilt and push apart to reduce the overlap of the amino groups. The thermodynamic data show that the T-T mismatch is less destabilizing than the A-A mismatch when flanked by C-G base pairs in this sequence, in contrast to their approximately equal stabilities when flanked by A-T base pairs in the sequence d(CAAAXAAAG.CTTTYTTTG) where X and Y = A, C, G, and T [Aboul-ela, F., Koh, D., & Tinoco, I., Jr. (1985) Nucleic Acids Res. 13, 4811]. Although the mechanism cannot be determined conclusively from the limited data obtained, exchange of the imino protons with solvent in these destabilized heteroduplexes appears to occur by a cooperative mechanism in which half the helix dissociates.

Base Sequence↗
PubMed1986

The tetraribonucleotide rCpGpCpG forms a left-handed Z-RNA double-helix.

NMR and circular dichroism studies show that the RNA tetranucleotide rCpGpCpG can form a Z-RNA left-handed double-helix. In 1.0 M NaClO4, circular dichroism measurements indicate that the tetramer is in the A-form. In 6.0 M NaClO4, there is a characteristic change in the circular dichroism, indicating that the tetramer adopts a left-handed Z-form. This conformation is verified by phosphorus and proton NMR studies. The 31P spectrum shows a large downfield shift in one of the resonances upon an increase in salt concentration. Proton nuclear Overhauser effect (NOE) experiments indicate that the guanosines are in the syn conformation. These results are consistent with the formation of a Z-form double-helix.

Base Sequence↗
PubMed1985

Evidence for Z-form RNA by vacuum UV circular dichroism.

Circular dichroism (CD) spectra in the vacuum UV region for different conformations of poly d(G-C) X poly d(G-C) and poly r(G-C) X poly r(G-C) are very characteristic. The CD of the RNA in the A-form (6 M NaClO4 and 22 degrees C) is very similar to that of the DNA in 80% alcohol where it is believed to be in the A-form. With the exception of the longest wavelength transition, the CD of the RNA in 6 M NaClO4 at 46 degrees C is similar to the CD of the DNA under conditions where it is believed to be in the Z-form (2 M NaClO4). This substantiates that poly r(G-C) X poly r(G-C) assumes a left-handed Z-conformation in 6 M NaClO4 above 35 degrees C. CD spectra for the left-handed Z-forms of both the RNA and DNA are characterized by an intense negative peak at 190-195 nm, a crossover at about 184 nm, and an intense positive peak below 180 nm. The right-handed A- and B-forms of RNA and DNA all have an intense positive peak in their CD spectra near 186 nm. The large difference in CD in the range 185-195 nm for right- and left-handed conformations of nucleic acids can be used to identify the sense of helix winding.

Circular Dichroism↗
PubMed1985

Extensive synthesis of poly[r(G-C)] using Escherichia coli RNA polymerase.

Conditions have been found that allow for extensive synthesis of poly[r(G-C)] using Escherichia coli RNA polymerase with a poly[d(I-C) X poly[d(I-C)] template. The extensive synthesis, in which many copies of the template were produced by the enzyme, continued for 24 h. Repeated addition of the template was necessary for synthesis to continue, as the poly[r(G-C)] appeared to be binding to the template, inhibiting transcription by the polymerase. Four hundred ODU, or 20 mg of the poly[r(G-C)] has been prepared using 0.3 mg of protein.

DNA-Directed RNA Polymerases↗
PubMed1981

Cyclic neutropenia. A tale of two brothers and their family.

A family history encompassing four generations is presented. Definite cyclic neutropenia has been noted in two generations. In one member, the symptoms abated as she grew older. One 12-year-old member died of clostridial septicemia secondary to gangrene of the terminal ileum. At autopsy he was found to have amyloidosis. A trial of lithium carbonate therapy was carried out in a 7-year-old male but a positive hematologic response was not obtained.

Adolescent↗
PubMed1976

Use of prothrombin complex concentrates in the treatment of a hemophilic patient with an inhibitor of factor VIII.

The course and treatment of a life-threatening hemorrhagic episode in a patient with hemophilia A whose plasma contained a high concentration of an inhibitor of factor VIII activity is presented. The inhibitor of factor VIII was localized to the most anodal fractions of immunoglobulin G on electrophoresis, and was thus presumed to be an antibody directed against factor VIII. No therapeutic benefit occurred with infusions of massive amounts of fresh blood and factor VIII concentrates, or with a brief course of immunosuppressive therapy. Administration of standard and activated prothrombin complex concentrates resulted in reduction of the partial thromboplastin time to almost normal values and control of hemorrhage. Eight months later, another hemorrhagic episode occurred. Although a higher titer of inhibitor of factor VIII activity was still present in the patient's plasma, a beneficial therapeutic response was again achieved with standard prothrombin complex infusions.

Adult↗