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Biomedical subjects

A Padilla

Publications and source records attributed to A Padilla.

49 records · Page 3Linked to original sources
PubMed1992

Leiomyosarcoma of the rectum.

Leiomyosarcoma of the rectum is a rare entity. Approximately 150 cases have been described in the literature. Differentiation from its benign counterpart, leiomyoma, and other connective-tissue tumors is often difficult, but it is important because each tumor has an entirely different prognosis. The case of a patient in whom an 11 x 5.5 cm leiomyosarcoma of the rectum was surgically excised by abdominoperineal resection is presented. Literature review shows disagreement over the therapeutic approach, most likely due to the lack of a large series of patients with this disease. At present, a selective treatment approach appears to be the most advocated. Lesions less than 2.5 cm in size and limited to the bowel wall can still be treated by wide local excision. More radical surgical resection is indicated for larger tumors and those extending outside the bowel wall.

Aged↗
PubMed1991

Statistical analysis of double NOE transfer pathways in proteins as measured in 3D NOE-NOE spectroscopy.

The recent development of three-dimensional NMR spectroscopy has alleviated the problem of overlap of resonances. However, also for the 3D experiments resonance assignment strategies have usually relied upon knowledge about spin systems, combined with information about short (sequential) distances. For doubly (15N/13C)-labelled molecules, a novel assignment strategy has been developed. In this paper we address the possibilities of an assignment strategy for proteins, based solely upon the use of NOE data. For this, the 3D NOE-NOE experiment seems most suitable. Therefore, we have made a theoretical evaluation of double NOE transfer pathways in 28 protein crystal structures. We identify 95 connectivities which are most likely to be observed as cross peaks in a 3D NOE-NOE spectrum of a protein. Given the occurrence of one of these 95 connectivities, we evaluate the chances of occurrence for the others. Analysis of these conditional probabilities allowed the construction of five patterns of related, highly correlated cross peaks which resemble the conventional idea of spin systems to some extent and may provide a basis for assignment and secondary structure analysis from 3D NOE-NOE data alone.

Enzymes↗
PubMed1990

Assignment strategies in homonuclear three-dimensional 1H NMR spectra of proteins.

The increase in dimensionality of three-dimensional (3D) NMR greatly enhances the spectral resolution in comparison to 2D NMR. It alleviates the problem of resonance overlap and may extend the range of molecules amenable to structure determination by high-resolution NRM spectroscopy. Here, we present strategies for the assignment of protein resonances from homonuclear nonselective 3D NOE-HOHAHA spectra. A notation for connectivities between protons, corresponding to cross peaks in 3D spectra, is introduced. We show how spin systems can be identified by tracing cross-peak patterns in cross sections perpendicular to the three frequency axes. The observable 3D sequential connectivities in proteins are tabulated, and estimates for the relative intensities of the corresponding cross peaks are given for alpha-helical and beta-sheet conformations. Intensities of the cross peaks in the 3D spectrum of pike III parvalbumin follow the predictions. The sequential-assignment procedure is illustrated for loop regions, extended and alpha-helical conformations for the residues Ala 54-Leu 63 of parvalbumin. NOEs that were not previously identified in 2D spectra of parvalbumin due to overlap are found.

Hydrogen↗
PubMed1990

Immunodiagnosis of human cysticercosis in cerebrospinal fluid. Antigens from murine Taenia crassiceps cysticerci effectively substitute those from porcine Taenia solium.

Tapeworm antigens from Taenia crassiceps performed as well as those antigens from Taenia solium in an enzyme-linked immunosorbent assay for the detection of Cysticercus antibodies in 96 cerebrospinal fluid samples from patients with neurocysticercosis and in 96 CSF samples from patients with other varied neurological ailments. Thus, this manageable murine model of experimental cysticercosis solved the problem of antigen supply for clinical and epidemiological applications, and it provided an immediate means of abundant production of antigens for the wide distribution and standardization of immunodiagnostic tests for cysticercosis.

Animals↗
PubMed1989

The amino-terminal domain of LexA repressor is alpha-helical but differs from canonical helix-turn-helix proteins: a two-dimensional 1H NMR study.

The amino-terminal DNA binding domain of LexA repressor consisting of 84 amino acid residues has been studied by two-dimensional 1H NMR. Sequence-specific 1H resonance assignments were made for the first 60 amino acid residues. The secondary structure of this part of the protein contains three alpha-helices in the peptide segments 8-20, 28-35, and 41-54. The last helix has a distortion around residues 47-48. The peptide segment 28-47 shows weak homology with other helix-turn-helix proteins. To investigate the spatial structure of this region of the molecule distance-geometry calculations were performed based on proton-proton distance constraints from nuclear Overhauser effects. The resulting structure shows that the segment 28-47 contains two helices with a loop region between them. The relative orientation of the two helices is similar to that found in helix-turn-helix proteins, but the helices are further apart, with the phenyl ring of Phe-37 located between them. The Brookhaven Protein Data Bank was searched for structurally homologous peptide segments in other proteins. The result of this search was that the two-helical structure of LexA is not more closely related to the canonical helix-turn-helix motif than it is to similar substructures found in other classes of proteins.

Amino Acid Sequence↗
PubMed1988

Two-dimensional 1H nuclear magnetic resonance study of pike pI 5.0 parvalbumin (Esox lucius). Sequential resonance assignments and folding of the polypeptide chain.

The structure of alpha pike 5.0 parvalbumin under its Ca-loaded form (or PaCa2) is studied in solution by two-dimensional 1H nuclear magnetic resonance (n.m.r.) at 360 MHz using a conventional strategy of sequential assignments, which involved correlated spectroscopy, relayed coherence transfer spectroscopy and nuclear Overhauser enhancement spectroscopy. In order to overcome the problem of spectral overlapping due to the presence of 108 residues in the protein, experiments were performed at different pH and temperature values, either in 1H2O or in 2H2O solutions. The amino acid sequence of pike 5.0 parvalbumin is thus fully characterized by nearly the totality of its NH, C alpha H and C beta H resonances originating from the different residues (421 protons assigned among 429 in total). When associated with the remaining side resonances, these sequence-specific assignments provide a basis for establishing the secondary organization and tertiary folding of the polypeptide chain. Pike 5.0 parvalbumin was selected as a characteristic representative of the alpha phylogenic series, for which no crystalline structure is presently available, in contrast with the beta series for which two crystalline structures have been determined. A parvalbumin molecule with a single polypeptide chain of 108 amino acids represents one of the highest molecular weights analyzed so far by two-dimensional n.m.r. spectroscopy. The use of a moderate magnetic field strength, with 1H nuclei resonating at 360 MHz, is justified by the fact that ring current effects are operating favorably in this globular protein with a high phenylalanine content. A three-dimensional structure has been generated by the "distance geometry" or DISGEO computational procedure on the basis of about 450 interproton nuclear Overhauser enhancement connectives (short, medium and long-range) in conjunction with a selection of phi and chi dihedral angle constraints. The coherence of the calculated structure, which displays all the features of the typical folding of a parvalbumin protein, provides a good test of reliability of the n.m.r. data collected so far. Although similar to a beta parvalbumin in the folding of its polypeptide chain, the alpha parvalbumin studied here differs markedly from a beta parvalbumin in the length of its C-terminal F-helix domain, which includes 11 residues instead of ten in the latter.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMedDate not supplied

Kinetics of amide proton exchange in parvalbumin studied by 1H 2-D NMR. A comparison of the calcium and magnesium loaded forms.

The amide proton exchange rates have been measured for the pike parvalbumin loaded either with calcium (PaCa2) or with magnesium (PaMg2) by using 2-D total correlation spectroscopy experiments. The differences in the exchange rates observed between these two species were unexpected when compared with the small conformational changes induced in parvalbumin by the Ca/Mg exchange. With the calcium-loaded protein (PaCa2), a significant difference was observed for the amide proton exchange rates of residues located in the N-terminal domain AB in contrast to the slower exchange rates that were observed in the CD and EF domains. Such a difference does not exist for PaMg2, where faster exchange rates are observed over all the sequence. Since amide proton exchange rates are the signature of the solvent's accessibility in proteins, we interpreted our results in terms of difference of the equilibria between 'closed-states' and 'opened-states' for individual amide protons of the protein when calcium was replaced by magnesium. The CD and EF domains, and to a lesser extent the AB domain, would be more rigid when the protein was loaded with calcium ions. For the magnesium-loaded parvalbumin (PaMg2) the faster exchange rates we observed could be rationalized by a more flexible structure than in the case of the PaCa2.

Amides↗
PubMedDate not supplied

Barriers to recognition of erectile dysfunction among diabetic Mexican-American men.

BACKGROUND: Diabetes is widespread among Mexican-Americans, and erectile dysfunction is a well-recognized complication for which effective treatments are available. Men who desire treatment, however, might not volunteer erectile complaints to their physician, especially across cultural lines. METHODS: We surveyed diabetic Mexican-American men cared for in two community health centers to estimate the prevalence of self-reported erectile dysfunction, to learn how frequently they discuss sexual function with their physician, and to evaluate factors that facilitate or inhibit discussion. RESULTS: Of the participants surveyed, 59 percent (95 percent confidence interval [CI] 48-70) reported always lacking erection in one or more proposed circumstances, whereas 82 percent (95 percent CI 73-91) reported frequent erectile insufficiency in the same circumstances. Patients reporting erectile problems were no more likely to have discussed sexual function with their physician than those who denied frequent erectile dysfunction. Of those with frequent erectile dysfunction, only 47 percent had had a discussion about sexual function with their physician. We found that these men did not initiate discussion because they were embarrassed or expect the physician to initiate the dialogue. CONCLUSIONS: Erectile dysfunction is common in diabetic Mexican-American men and is underrecognized by clinicians and underreported by patients. Because effective treatments exist, primary care physicians should routinely ask their diabetic patients about erectile function.

Adult↗
PubMedDate not supplied

[Seroepidemiology of cysticercosis in Mexico].

The seroprevalence of cysticercosis indicate that there is a high risk of contact with Taenia solium in Mexico, including both genders and all regions, socioeconomic group, and ages. There are some statistically significant differences in risk of contact, affecting principally the center and southeast of the country, rural areas, handicapped persons, children, old people and women. However, these differences are small. This study emphasizes the fact that the risks of infection by Taenia solium are important in all groups, and therefore, the programs for the control of this disease should be focused at the entire population and emphasize strategies for social development.

Adolescent↗
PubMedDate not supplied

[Numerical analysis of western blot digitalized images. The case of HIV].

The present work explores the use of image digitalization of western blot (WB) aiming to extract more information about the humoral immune response of human immunodeficiency virus (HIV) infected individuals, and to analyze obtained data in a multivariate manner. The digitalization and analysis of WB images was performed on 115 sera. Images were analyzed either qualitatively: dendogram and principal component analysis (PCA) or quantitatively: PCA of the total bands, taking either the antigens, which belong to the virus, or only those which do not. Results show the feasibility of mechanical diagnosis of a large number of WB images. The dendogram and the qualitative PCA satisfactorily separated white images, images with less than four bands, and images with more complex patterns. Quantitative analysis, which keeps more information, separated the images of negative, undetermined and positive diagnosis quite precisely. It was also found that the positive images with complex patterns of antigen recognition correlate better with asymptomatic individuals. Image analysis also revealed various other bands in WB which do not seem to correspond to viral proteins and could represent autoantigens or crossed antigens between HIV and humans which may cause autoimmunity. Digital analysis of WB images is thus demonstrated to be of great usefulness in the diagnosis and of potential great interest in following the evolution and exploring the pathogenesis of AIDS.

AIDS Serodiagnosis↗