Search PubMed⌕ Search

Biomedical subjects

S Maldonado

Publications and source records attributed to S Maldonado.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of cytomegalovirus viral load measure by real-time PCR with pp65 antigenemia for the diagnosis of cytomegalovirus disease in solid organ transplant patients.

Cytomegalovirus (CMV) infection is the most frequent complication in solid organ transplant recipients. Currently, the antigenemia assay is widely used to detect this infection, although its success is being questioned to a great extent nowadays. The aim of our study is to compare a quantitative real time PCR to measure CMV DNA to the antigenemia assay, for the diagnosis to CMV disease. For our research, we prospectively processed 1198 samples (plasma and peripheral blood leukocytes [PBMC]), which belonged to 158 transplant recipients. In every sample the detection of the pp65 antigen in PBMC was carried out, as well as the quantification of CMV DNA by PCR (Light Cycler, LC-PCR). For this process, FRET probes, which detect a 254-bp fragment from the CMV gB gene, were used. The dynamic range of the LC-PCR was 500 to 5.10(7) copies/mL plasma and from 62 to 6.10(6) copies/10(6) PBMC. Twenty-three episodes of cytomegalovirus (CMV) disease occurred in 22 out of 158 patients and PCR displayed levels of sensitivity and specificity of 100% and 67%, respectively. The antigenemia assay obtained values of 91% and 57%. We established a cutoff value of 10(3) copies/mL plasma and 315 copies/10(6) cells. According to these cutoff values, PCR showed levels of sensitivity, specificity, VPN and VPP of 95.6%, 81.6%, 99%, and 53% respectively. Moreover, the LC-PCR assay anticipated the antigenemia assay in 10 patients out of 22 who developed CMV disease and the appearance of any clinical symptoms in 12 out of 22 patients. In conclusion, we believe that the quantification of CMV DNA by LC-PCR is a superior assay to pp65 antigenemia test regarding the early diagnosis of CMV disease in solid organ transplant recipients.

Cytomegalovirus↗
PubMed2003

A cytoplasmically inherited mutant controlling early chloroplast development in barley seedlings.

Cytoplasmic line 2 (CL2) has been previously reported as a cytoplasmically inherited chlorophyll-deficient mutant selected from a chloroplast-mutator genotype of barley. It was characterized by a localized effect on the upper part of the first-leaf blade. At emergence the CL2 seedlings-phenotype varied from a grainy light green to an albino color. They gradually greened during the following days, starting from the base of the blade and extending to cover most of its surface when it was fully grown. The present results, from both light microscopy and transmission electron microscopy (TEM), confirmed the previously described positional and time-dependent expression of the CL2 syndrome along the first-leaf blade. During the first days after emergence, light microscopy showed a normally developed chloroplast at the middle part of the CL2 first-leaf blade, meanwhile at the tip only small plastids were observed. TEM showed that the shapes and the internal structure of the small plastids were abnormal, presenting features of proplastids, amyloplasts and/or senescent gerontoplasts. Besides, they lack plastid ribosomes, contrasting with what was observed inside chloroplasts from normal tips, which presented abundant ribosomes. Phenotypic observations and spectrophotometric analysis of seedlings produced by mother plants that had been grown under different temperatures indicated that higher temperatures during seed formation were negatively associated with pigment content in CL2 seedlings. In contrast, higher temperatures during the growth of CL2 seedlings have been associated with increased pigment content. Aqueous solution with kanamycin and streptomycin, which are antibiotics known to interfere with plastid gene translation, were used for imbibition of wild-type and CL2 seeds. Antibiotic treatments differentially reduced the chlorophyll content in the upper part of the first-leaf blade in CL2, but not in wild-type seedlings. These results suggest that in the wild-type, plastid-gene proteins which are necessary for chloroplast development and chlorophyll synthesis in the upper part of the first-leaf blade are usually synthesized during embryogenesis. However, under certain circumstances, in CL2 seedlings, they would be synthesized after germination. In addition, a shortening of the sheath has been observed in association with pigment decrease suggesting the existence of plastid factors affecting the expression of some nuclear genes. We consider the CL2 mutant a unique experimental material useful to study biological phenomena and external factors regulating plastid, and nuclear gene expression during embryogenesis and early seedling development.

Cytoplasm↗
PubMed2002

Influence of body mass and height on the energy cost of running in highly trained middle- and long-distance runners.

Previous studies about the influence of body dimensions on running economy have not compared athletes specialized in different competition events. Therefore, the purpose of the present study was to assess the influence of body mass (m(b)) and height (h) on the energy cost of running (Cr) in 38 highly trained male runners, specialized in either marathon (M, n = 12), long middle-distance (5000 - 10000 m, LMD, n = 14) or short middle-distance (800 - 1500 m, SMD, n = 12), and to assess possible differences in body dimensions for each event. Subjects performed a progressive maximal exercise on the treadmill to determine oxygen uptake VO(2)) at different submaximal velocities and maximal oxygen uptake VO(2)max). Cr was calculated from VO(2) measurements. LMD runners had significantly higher mean Cr (0.192 +/- 0.007, 0.182 +/- 0.009, and 0.180 +/- 0.009 ml O(2) x kg(-1) x m(-1) for LMD, M and SMD, respectively) and VO(2)max (74.1 +/- 3.7, 68.5 +/- 2.9 and 69.7 +/- 3.4 ml x kg (-1) x min (-1)). Cr correlated with h (r = -0.86, p < 0.001) and m(b) (r = -0.77, p < 0.01) only in the SMD group. In conclusion, these data suggest that highly trained distance runners tend to show counterbalancing profiles of running economy and VO(2)max (the higher Cr, the higher VO(2) max and vice versa), and that anthropometric characteristics related with good performance are different in long-distance and middle-distance events.

Adult↗
PubMed2001

Anabaena apoflavodoxin hydrogen exchange: on the stable exchange core of the alpha/beta(21345) flavodoxin-like family.

An important issue in modern protein biophysics is whether structurally homologous proteins share common stability and/or folding features. Flavodoxin is an archetypal alpha/beta protein organized in three layers: a central beta-sheet (strand order 21345) flanked by helices 1 and 5 on one side and helices 2, 3, and 4 on the opposite side. The backbone internal dynamics of the apoflavodoxin from Anabaena is analyzed here by the hydrogen exchange method. The hydrogen exchange rates indicate that 46 amide protons, distributed throughout the structure of apoflavodoxin, exchange relatively slowly at pH 7.0 (k(ex) < 10(-1) min(-1)). According to their distribution in the structure, protein stability is highest on the beta-sheet, helix 4, and on the layer formed by helices 1 and 5. The exchange kinetics of Anabaena apoflavodoxin was compared with those of the apoflavodoxin from Azotobacter, with which it shares a 48% sequence identity, and with Che Y and cutinase, two other alpha/beta (21345) proteins with no significant sequence homology with flavodoxins. Both similarities and differences are observed in the cores of these proteins. It is of interest that a cluster of a few structurally equivalent residues in the central beta-strands and in helix 5 is common to the cores.

Amino Acid Sequence↗
PubMed2001

Immunolocalization of alkaloids and X-ray microanalysis of elements in lupin seeds.

Immunolocalization of alkaloids in lupin seeds (Lupinus spp.) has been performed by cryofixation and conventional methods. Alkaloids were localized in the protein bodies of the cotyledon cells. Some immunogold particles in the walls of these cells were also observed. There were no differences in the sites of localization between the two mentioned methods. X-ray microanalysis of elements showed the presence of P, Mg, S, and K in the protein bodies of cotyledon cells in lupin seeds. The role of K+ in alkaloids transport is discussed.

Alkaloids↗
PubMed2001

Stabilization of apoflavodoxin by replacing hydrogen-bonded charged Asp or Glu residues by the neutral isosteric Asn or Gln.

Knowledge of protein stability principles provides a means to increase protein stability in a rational way. Here we explore the feasibility of stabilizing proteins by replacing solvent-exposed hydrogen-bonded charged Asp or Glu residues by the neutral isosteric Asn or GLN: The rationale behind this is a previous observation that, in some cases, neutral hydrogen bonds may be more stable that charged ones. We identified, in the apoflavodoxin from Anabaena PCC 7119, three surface-exposed aspartate or glutamate residues involved in hydrogen bonding with a single partner and we mutated them to asparagine or glutamine, respectively. The effect of the mutations on apoflavodoxin stability was measured by both urea and temperature denaturation. We observed that the three mutant proteins are more stable than wild-type (on average 0.43 kcal/mol from urea denaturation and 2.8 degrees C from a two-state analysis of fluorescence thermal unfolding data). At high ionic strength, where potential electrostatic repulsions in the acidic apoflavodoxin should be masked, the three mutants are similarly more stable (on average 0.46 kcal/mol). To rule out further that the stabilization observed is due to removal of electrostatic repulsions in apoflavodoxin upon mutation, we analysed three control mutants and showed that, when the charged residue mutated to a neutral one is not hydrogen bonded, there is no general stabilizing effect. Replacing hydrogen-bonded charged Asp or Glu residues by Asn or Gln, respectively, could be a straightforward strategy to increase protein stability.

Amino Acid Substitution↗
PubMed2001

Transgenic tobacco plants expressing the potato virus X open reading frame 3 gene develop specific resistance and necrotic ring symptoms after infection with the homologous virus.

Tobacco plants were transformed with the open reading frame 3 gene from Potato virus X (PVX) coding for the p12 protein. Although the transgenic plants exhibited a normal morphological aspect, microscopic examination revealed extensive alterations in leaf tissue structure. After being challenged with PVX, the transgenic plants showed resistance to PVX infection and formation of specific leaf symptoms consisting of concentric rings encircled by necrotic borders. These novel symptoms were accompanied by biochemical changes normally associated with the hypersensitive response (HR) and were absent in noninfected transgenic plants or in PVX-infected nontransgenic plants. No equivalent virus resistance was observed after inoculation with Tobacco mosaic virus or Potato virus Y, suggesting the presence of a specific resistance mechanism. Despite development of HR-like symptoms, systemic acquired resistance was not induced in PVX-infected p12 transgenic plants. No evidence of an RNA-mediated resistance mechanism was found.

Capsid↗
PubMed2001

Bronchiolitis obliterans organizing pneumonia associated with Evans syndrome.

The association of bronchiolitis obliterans organizing pneumonia (BOOP) with insulin-dependent diabetes mellitus (IDDM) and Evans syndrome (autoimmune pancytopenia) has not been reported previously. We describe the case of a 4-year-old child diagnosed with IDDM and Evans syndrome who presented malaise, fever and nonproductive cough for several months. The chest radiograph revealed several patchy alveolar opacities with peripheral and bilateral distribution and multiple hilar and mediastinal adenopathies. An open lung biopsy established the diagnosis of BOOP. During the follow-up over the next 7 years, the patient had chronic relapses in spite of corticosteroid treatment and developed restrictive lung disease.

Autoimmune Diseases↗
PubMed2001

A-549 is a suitable cell line for primary isolation of coxsackie B viruses.

A common receptor for coxsackie B virus and adenovirus has been described recently in cells of human and murine origin. Since the established cell line A-549 is suitable for adenoviruses, the potential use of A-549 cells for the isolation of coxsackie B viruses from clinical samples was investigated. All throat swabs sent to the laboratory between April 1998 and June 1999 were inoculated onto monolayers of MRC-5 and A-549 cells in tubes, and the enterovirus isolates obtained were typed. From April to June 1999, A-549 cells were compared prospectively to Buffalo green monkey (BGM) cells, considered as the most susceptible cell line for isolating coxsackie B viruses. Fifty-six out of 171 enterovirus isolates (33%) displayed a cytopathic effect (CPE) in the A-549 monolayer only, 48 isolates (28%) in the MRC-5 monolayer only, and 67 isolates (39%) in both cell lines. Most isolates that showed CPE in A-549 cells only (48 out of 56, 86%) were coxsackie B viruses, belonging to four different serotypes (B1, B2, B4, and B6). When BGM and A-549 cells were inoculated in parallel, both recovered the same number of coxsackie B isolates (n = 20), and the CPE was noted on approximately the same day. In conclusion, growth in A-549 but not MRC-5 cells identified coxsackie B viruses in most cases. A-549 was comparable to BGM for primary isolation of coxsackie B viruses.

Cell Line↗
PubMed2000

Thalamic terminal fields of individual axons from the ventral part of the dentate nucleus of the cerebellum in Macaca mulatta.

This study examined organization of the projection from the dentate nucleus of the cerebellum to the ventral lateral nucleus (VL) of the thalamus in Macaca mulatta. Small injections of biotinylated dextran amine were placed in the ventral parts of dentate nuclei. The distribution of all contralateral terminal fields in the thalamus was charted, and representative individual axons that terminated in the VL were traced in serial sections under the light microscope. These axons were reconstructed with all their branches and terminal fields in the thalamus. The geometry and size of the terminal fields as well as the number and distribution of boutons and neurons in them were analyzed. The terminal fields of all labeled axons were distributed widely over the VL either singly or in clusters. Two types of axons were found: simple axons formed only one terminal field and complex axons formed multiple terminal fields at a distance. Individual terminal fields were focal, had the form of flattened discs, and generated up to 200 boutons distributed between 10 and 29 nerve cell bodies. These findings suggest that a simple axon activates a small group of neurons at one site. The complex axons, in turn, influence similar size cell groups at different VL locations. The total number of boutons generated by a single complex axon was up to 300. Future studies should determine whether simple axons could be branches of complex axons that took off below the thalamus. The results reveal a complex organization of the input from the ventral dentate to the VL that only partially fits into the traditional concept of somatotopic organization of the nucleus.

Animals↗
PubMed2000

Generalized eruptive keratoacanthoma (Grzybowski variant).

We describe a patient with generalized eruptive keratoacanthoma (KA) of Grzybowski showing the characteristic features of this extremely rare condition. Since the first description by Grzybowski in 1950, only 28 additional cases (including the present one) have been reported. This variety of KA most commonly affects patients during the fifth to seventh decade of life and appears as a generalized eruption of hundreds to thousands of follicular papules. The small pruriginous papules often have a keratotic centre and show microscopic features of KA. Marked facial involvement is characteristic and can lead to masked facies with ectropion, as in our patient. The course of the disease is chronic and the response to therapy is poor.

Acitretin↗
PubMed2000

A new model for experimental tendon adhesions in the chicken.

A minimally invasive model using a manual abrader to induce adhesions in the chicken's central digit is described. The flexor synovial sheath and the profundus tendon were abraded with access through small flaps at the level of the proximal and distal phalanges of the avian long toes. The birds were divided into two groups according to the severity of the induced trauma. Group I birds received an abrasion injury and were euthanized to allow biomechanical testing 5 weeks postoperatively. Group II birds had a more severe abrasion and were euthanized similarly and tested 5 weeks after surgery. Results were compared with nonsurgical controls. Long toe function was evaluated weekly by measuring (1) the range of active flexion of each interphalangeal joint, resolved to total angular range; (2) the grasping ability on graded-diameter perches; and (3) the flexion deficit of the long toe. Postmortem biomechanical properties of the adhesions were measured. There was a significant difference between the unoperated controls and abraded digits of both groups in all parameters (p < 0.001). There was, in addition, a marked change in most of the measured parameters between groups I and II. In group I digits the functional and biomechanical deficit was less than group II. In summary, this animal model of long-segment abrasive injury to the tendon and sheath is a simple and reproducible method to generate adhesions and can be used for the evaluation of treatment modalities for adhesion prevention.

Animals↗
PubMed2000

Angiotensin II increases host resistance to peritonitis.

Studies by other laboratories have shown that angiotensin II (AII) can affect the function of cells which comprise the immune system. In the present study, the effect of AII on the function of peritoneal macrophages and peripheral blood monocytes was assessed. In vitro exposure (4 h prior to assay) of peritoneal macrophages from mice and rats to AII increased the percentage of cells that phagocytosed opsonized yeast and the number of yeast per macrophage. Furthermore, AII increased the respiratory burst capacity of peritoneal macrophages from mice and rats and peripheral blood mononuclear cells from humans. Because of these observations, the effect of AII on host resistance to bacterial infection was assessed. Intraperitoneal administration of AII was shown to increase host resistance (reduced abscess formation) in an animal model of bacterial peritonitis. Studies were then conducted to assess whether parenteral administration of AII, a clinically relevant route, could affect peritoneal host resistance in a manner similar to that observed after peritoneal administration. These studies showed that subcutaneous administration of AII throughout the postinfection interval increased the level of host resistance to bacterial peritonitis. Furthermore, in a study which compared AII and Neupogen, an agent approved for use for the reduction of febrile neutropenia after myeloablative therapy, daily subcutaneous administration of AII reduced abscess size and incidence, whereas Neupogen did not have any therapeutic benefit in this model. These data suggest that AII may be of therapeutic benefit as an immunomodulatory agent.

Angiotensin II↗
PubMed2000

[Chemical composition and mineral content of legumes and cereals produced in Northwestern Argentina].

Different varieties of bean (Phaseolus vulgaris), corn (Zea mayz), lentil (Lens sp), soya (Glycine max) and wheat (Tricticum sp) were analyzed in order to obtaining data of chemical composition and content of minerals to contribute to the International Food Data System INFOODS in the elaboration of Regional Food Composition Tables and to evaluate the quality of grains. The selected varieties were the ones produced in the northwestern region of Argentina. The beans were divided in five groups, according to their statistical similarity. The pallares variety is the one that presents bigger content of Cu (2.42 mg/100 g), Fe (76.03 mg/100 g) and Zn (6.08 mg/100 g). The samples of corn were divided in three groups, according to their statistical similarity. The leales yellow corn has bigger content of Zn (3.16 mg/100 g) that the other varieties of the region. The 8 rayas white corn is the one that presents bigger content of Fe (11.48 mg/100 g), while the pisingallo yellow corn is that of bigger content of Cu (1.21 mg/100 g).

Argentina↗
PubMed1999

Composition of different bean varieties (Phaseolus vulgaris) of Northwestern Argentina (Region NOA): cultivation zone influence.

There have been prior investigations concerning the environmental effects and especially soil conditions upon the proximate analysis and mineral content of grains. However, the studies are not complete and have not involved beans grown in the northwestern regions of Argentina. For this reason, this study was initiated to determine the concentration of protein, moisture, ash, fat, and minerals of various bean samples grown in northwestern Argentina. Six varieties of beans were taken from seven different regions. AOAC standard methods were used for chemical analysis. The elements analyzed for all bean samples show that moisture varies from 12 to 14%, proteins from 18 to 22%, fat from 0.7 to 1.20%, copper from 0.8 to 1.20 mg/100 g, iron from 9 to 18 mg/100 g, zinc from 2.5 to 4 mg/100 g, and phosphorus from 295 to 542 mg/100 g. No arsenic was detected in the bean samples. Different analyzed bean varieties were significantly different for proximate composition and mineral content, and each variety from different regions of northwestern Argentina present significant differences.

Argentina↗
PubMed1999

Population pharmacokinetics. A regulatory perspective.

The application of population approaches to drug development is recommended in several US Food and Drug Administration (FDA) guidance documents. Population pharmacokinetic (and pharmacodynamic) techniques enable identification of the sources of inter- and intra-individual variability that impinge upon drug safety and efficacy. This article briefly discusses the 2-stage approach to the estimation of population pharmacokinetic parameters, which requires serial multiple measurements on each participant, and comprehensively reviews the nonlinear mixed-effects modelling approach, which can be applied in situations where extensive sampling is not done on all or any of the participants. Certain preliminary information, such as the compartment model used in describing the pharmacokinetics of the drug, is required for a population pharmacokinetic study. The practical design considerations of the location of sampling times, number of samples/participants and the need to sample an individual more than once should be borne in mind. Simulation may be useful for choosing the study design that will best meet study objectives. The objectives of the population pharmacokinetic study can be secondary to the objectives of the primary clinical study (in which case an add-on population pharmacokinetic protocol may be needed) or primary (when a stand-alone protocol is required). Having protocols for population pharmacokinetic studies is an integral part of 'good pharmacometric practice'. Real-time data assembly and analysis permit an ongoing evaluation of site compliance with the study protocol and provide the opportunity to correct violations of study procedures. Adequate policies and procedures should be in place for study blind maintenance. Real-time data assembly creates the opportunity for detecting and correcting errors in concentration-time data, drug administration history and covariate data. Population pharmacokinetic analyses may be undertaken in 3 interwoven steps: exploratory data analysis, model development and model validation (i.e. predictive performance). Documentation for regulatory purposes should include a complete inventory of key runs in the analyses undertaken (with flow diagrams if possible), accompanied by articulation of objectives, assumptions and hypotheses. Use of diagnostic analyses of goodness of fit as evidence of reliability of results is advised. Finally, the use of stability testing or model validation may be warranted to support label claims. The opinions expressed in this article were revised by incorporating comments from various sources and published by the FDA as 'Guidance for Industry: Population Pharmacokinetics' (see the FDA home page http:/(/)www.fda.gov for further information).

Data Interpretation, Statistical↗