VIR.II: a new interface with the antibody sequences in the Kabat database.

The Kabat database is the source of information par excellence on antibody sequences. In 1995, we developed an interface with the Kabat database, called VIR. VIR has been very useful in conducting studies aiming to find structure-function relationships in antibodies. Here we report a new version adapted to the World Wide Web, called VIR.II. VIR.II allows searches by type of chain (V(H) or V(L)), by species, and by specificity. The species are selected using a pulldown menu, whereas the specificities can be selected from a list containing the unique specificities reported in the Kabat database. These facilities avoid mistakes and redundancies in the searches. Another feature, and probably the most important one, is that VIR.II introduces a classification of specificities in terms of the chemical and biochemical nature of the antigen, like anti-protein, anti-peptide, anti-hapten, etc. This classification has been useful in discovering patterns in the antigen-binding site of antibodies that correlate with the type of antigen the antibody interacts with. To illustrate this, while showing the capabilities of VIR.II, we analyze all the murine anti-peptide and anti-protein antibody sequences compiled as of July, 2000 in the Kabat database.

Analysis of antibodies of known structure suggests a lack of correspondence between the residues in contact with the antigen and those modified by somatic hypermutation.

Forty unique murine antibody-antigen complexes determined at 2.5 A or less resolution are analyzed to determine whether the residues in direct contact with the antigen are modified by somatic hypermutation. This was done by taking advantage of the recent characterization of the pool of Vkappa germline genes of the mouse. The average number of residues in contact with the antigen in the V(L) gene, which contains the CDRL-1, CDRL-2, and all but one residue of CDRL-3, was six. The average number of somatic mutations was similar (around five). However, as many as 53% of the antibodies did not show somatic replacements of residues in contact with the antigen. Another 28% had only one. Overall, the frequency of antibodies with increasing number of somatic replacements in residues in contact with the antigen decreased exponentially. A possible explanation of this finding is that mutations in the contacting residues have an adverse effect on the antigen-antibody interaction. This implies that most of the observed mutations are those remaining after negative (purifying) selection. Therefore, efficient strategies of site-directed mutagenesis to improve the affinity of antibodies should be focused on residues other than those directly interacting with the antigen.

[Wolff-Parkinson-White syndrome cured with diagnostic electrode catheter]. / Curación del síndrome de Wolff-Parkinson-White con electrocatéter diagnóstico.

Catheter-induced mechanical trauma to accessory pathways is an infrequent, usually transitory phenomenon related to manipulation of the ablation catheter. We describe a patient with Wolff-Parkinson-White syndrome due to a midseptal accessory pathway with recurrent episodes of paroxysmal tachycardias under antiarrhythmic treatment. During the diagnostic electrophysiological study coinciding with manipulation of the His catheter (5 French), mechanical trauma to the accessory pathways occurred, with preexcitation not being recovered in the midterm follow up (28 months). This is a exceptional case demonstrating the complexity of the decision making (expectant or rescue ablation) following accidental catheter-induced mechanical trauma.

[Spontaneous postpartum coronary dissection]. / Disección coronaria espontánea posparto.

We report a case of spontaneous dissection of right coronary artery diagnosed in a 31-year-old woman in the postpartum period, presenting with prolonged angina and ST segment elevation in the ECG, a rare manifestation of this extremely uncommon anatomico-clinic entity. We described the clinical presentation, the findings derived from transthoracic echocardiography and coronary arteriography, and the clinical course with medical therapy.

[Role of noninvasive examinations in the management of ischemic cardiopathy. V. Noninvasive examinations in the management of patients with chronic ischemic cardiopathy]. / Papel de las exploraciones no invasivas en el manejo de la cardiopatía isquémica. V. Las exploraciones no invasivas en el manejo de los pacientes con cardiopatía isquémica crónica. Recomendaciones para su utilización.

In the last few years the has been an enormous development in noninvasive testing in the field of clinical cardiology. In fact, excellent monographs on each one of these techniques have been published elsewhere, but fewer publications exist that treat the topic of their indications and use in an integrated way, except for in the most common clinical situations. In this paper, the treatment of patients who present chest pain, stable and unstable angina is discussed, including the study of postinfarction patients. Furthermore, the role of noninvasive tests in the detection of coronary heart disease in women and in patients with left bundle branch block is thoroughly analyzed; as well as their usefulness after surgical or percutaneous coronary revascularization and in patients with peripheral vascular disease.

[Usefulness of the Doppler index delta P/delta t in the evaluation of left ventricular systolic dysfunction]. / Utilidad del índice Doppler delta P/delta t en la evaluación de la disfunción sistólica ventricular izquierda.

INTRODUCTION AND OBJECTIVES: It has been shown that the delta P/delta t index, derived from the continuous Doppler mitral regurgitation signal correlates strongly with dP/dt. This study evaluates the feasibility, reproducibility and correlation of the index with ejection fraction and other conventional echocardiographic parameters. MATERIAL AND METHODS: One hundred and ten patients with mitral regurgitation demonstrated by colour Doppler were studied. delta P/delta t were calculated by the ratio between the interval of pression between two points of the Doppler signal (-1 and -3 m/s; 32 mmHg, applying the modified Bernouilli equation) and the interval of time (s) which separates both. Ejection fraction was measured in 70 patients by non-echocardiographic methods (isotopic ventriculography, n = 52, and angiography, n = 18). RESULTS: The index was feasible in 91 cases, the variability of intra and interobserver was 5% and 7% respectively. The correlation between delta P/delta t and ejection fraction was significant although weak (r = 0.59; p < 0.001; n = 70). It was better in the group of dilated idiopathic myocardiopathy (r = 0.72; p < 0.001; n = 18) than in the group of myocardial infarction (r = 0.54; p < 0.01; n = 25). No significant correlation was founded in the cases with mitral rheumatic valvulopathy. Regarding to the echocardiographic parameters, the best correlation was obtained with end systolic diameter (r = -0.64; p < 0.001; n = 49). Finally, a value of delta P/delta t < 1,000 mmHg/s predicted the existence of left ventricular systolic dysfunction with high accuracy (84%), sensitivity (80%) and specificity (92%). CONCLUSIONS: High feasibility when mitral regurgitation exists, adequate reproducibility and heightened precision in diagnosing left ventricular systolic dysfunction, are characteristics which make delta P/delta t useful in the echocardiographic routine practice.

The differences between the structural repertoires of VH germ-line gene segments of mice and humans: implication for the molecular mechanism of the immune response.

Although human and murine antibodies are similar when considering their diversification strategies, they differ in the proportion by which kappa and lambda type chains are present in their receptive V, repertoires. It has been shown that this difference implies a divergence in the structural repertoire of the kappa and lambda genes of these species. Nonetheless, the differences in VH have not been systematically studied. In this paper a systematic characterization of the VH structural repertoire of mice is made, so that a comparison with the VH structural repertoire of humans, described in detail elsewhere, could be properly accomplished. Our study shows the structural repertoire of mice to be dominated by canonical structure class 1-2 (approximately 60%), while in humans the dominant one is class 1-3 (approximately 40%). Analysis of the evolutionary relationships between human and mice suggest that this divergence may have a functional meaning. The implications of such findings are discussed.

Immunodominant synthetic peptides of Taenia crassiceps in murine and human cysticercosis.

The screening of a cDNA library of Taenia crassiceps revealed a clone designated KETc7 that induced high levels of protection against murine cysticercosis in previous experiments. The molecular structure of the deduced 100-amino acid sequence of the corresponding proline-rich polypeptide was studied to detect potentially immunologically active epitopes. Several candidate epitopes were identified, three of which were synthesized by solid-phase peptide synthesis and used as antigens in enzyme-linked immunosorbent assay (ELISA) for detection of specific antibodies in a selected panel of sera from mice infected with Taenia crassiceps and pigs infected with Taenia solium, as well as in the serum and cerebrospinal fluid of human patients with neurocysticercosis. The three peptides detected antibodies in serum from all infected mice. Seven of nine sera from patients with neurocysticercosis reacted strongly with peptide GK-3, and four of them with peptides GK-1 and GK-2. A lower reactivity was observed in sera from experimentally infected pigs. Peptide GK-3 reacted also with 45 out of 77 cerebrospinal fluids (CSF) from patients with confirmed neurocysticercosis and with 14 out of 68 CSF from control patients with other neurological disorders. This is the first report on synthetic peptides that are prominent in the humoral response of murine, porcine and human cysticercosis. Their identification implies finer molecular tools in the exploration of this form of host-parasite relationship, as well as hints to their application in immunodiagnosis and in vaccine design.

Frequency analysis of amino acids in the recognition regions of T-cell receptors.

In immunoglobulins (Igs), key amino acids in the Complementarity Determining Regions (CDR) are responsible for maintaining specific conformations called canonical structures. In T-cell receptors (TCRs), protein members of the Ig superfamily, the corresponding residues for maintaining these canonical structures have not been found. In previous studies we have found in Igs that the frequency of use of amino acids in some positions of the CDRs follows an inverse power law distribution, while the frequency of amino acids in the rest of the positions of the CDRs follows an exponential law distribution. The positions that follow the inverse power law distribution are precisely those involved in maintaining the canonical structures, while those positions for which the distribution fits the exponential distribution are those that should be properly involved in the recognition mechanism. In this paper, when the same analysis is applied to the use frequency of amino acids on the CDRs of TCRs, it is found that some positions that have been previously identified as having a structural role are those fitting the inverse power law. That finding combined with the cooperative or long-range interaction properties of systems that follow the inverse power law leads us to propose that the lack of determined key residues in certain positions is compensated by "equivalent' residues in other positions within the CDRs in order to maintain the canonical structures. Other positions that follow the exponential distribution are those which can be involved in the recognition process. These results coincide with a computer-generated model of TCR/peptide/MHC interaction previously published by the authors.

Canonical structure repertoire of the antigen-binding site of immunoglobulins suggests strong geometrical restrictions associated to the mechanism of immune recognition.

Is the structural repertoire of immunoglobulins free to adopt an almost infinite number of conformations to build the diversity of the immune response or does it take advantage of only a few conformations? In this paper we study this question by applying the canonical structure model to characterize the structural repertoire of immunoglobulins. The results found, indicate that only ten combinations out of the 300 possible different canonical structure classes (combinations of canonical structures), make up 87% of 381 sequences analyzed. This suggests that the structural repertoire of immunoglobulins is restricted to the preferential use of a small number of canonical structure classes. The possible functional significance of these results was studied by analyzing the correspondence between the observed canonical structural repertoire implicit in Ig sequences and the types of antigens recognized. Two different sets of canonical structure classes were distinguished: one with preference for some specific types of antigens like proteins, polysaccharides or haptens, and the other with multi-specific binding capabilities. Analysis of antibodies of known three-dimensional structure shows that for two specific classes, the canonical conformations of H2 and L1 determine the geometrical characteristics of the antigen-binding site, while at least in one multi-specific class, the changes in the general geometry of the antigen-binding site are produced by different conformations of H3. Implications of these results for the molecular recognition process mediated by immunoglobulins are discussed.

[Syncope and chest pain. Demonstration of the mechanism by the hyperventilation test]. / Síncope y dolor torácico. Demostración del mecanismo mediante test de hiperventilación.

Two patients admitted to hospital because syncope and chest pain are presented. In both patients, hyperventilation test caused severe myocardial ischaemia (ST segment elevation) and sudden development of presyncopal sustained ventricular tachycardia which immediately responded to intravenous nitroglycerin. The relationship between coronary vasospasm and sudden death secondary to polymorphic ventricular tachycardia is discussed. Also, the usefulness of the hyperventilation test to detect this problem and to monitor its therapeutic response is addressed.

Patterns in the complementary determining regions of immunoglobulins (CDRs).

An analysis of the frequency of use of amino acids on the CDR-1 and CDR-2 of 1500 immunoglobulins showed that the frequencies of amino acids in different positions could be fitted by two types of distribution. For some positions the frequencies were fitted by an inverse power law and for other positions by an exponential distribution. In order to see whether the more frequently used amino acids for specific positions had physicochemical properties or attributes in common, they were clustered using an algorithm normally applied to artificial intelligence problems. It was found that the amino acids in those positions fitted by the inverse power law have similar hydrophobicity and volume, which are commonly attributes of amino acids in structural positions. Thus, if these positions are critical to maintaining the structural features of the CDR domains, the rest of the positions should be either properly involved in the recognition process or irrelevant. The frequencies of amino acids in these recognition positions were fitted by the exponential law, and it was found by the clustering analysis that these amino acids share properties of a more general type, such as capability of forming hydrogen bonds, polarity, etc. This suggests that at least part of the recognition mechanism requires general properties rather than specific amino acids. Amino acids sharing the required attributes for each one of these positions are then used with random frequency.

A method for the quality control of osseointegration in endosseous implants.

Metallic dental and orthopedic implants are essential therapeutic tool. The biologic success of an implant involves intimate contact between the implant and vital bone tissue, an event which has been termed osseointegration. The aim of the present study was to study the biocompatibility and biomechanic properties of different implant materials. Zircalloy 4 metallic cones (1.8 mm base x 2 mm height) were implanted in the diaphysis of the tibiae of 6 Wistar rats (90 g body weight) under i.p. Ethyl Urethane anesthesia. The animals were killed 30 days postimplantation, the tibiae were resected, and radiographed. One side chosen at random was used for the biomechanical study; whereas the other implant of each animal was processed for embedding in methyl-methacrylate. The bond of the implanted material to bone tissue was monitored immediately after resecting the tibiae by applying an extraction force to the base of the cone via a device designed ad hoc connected to a testing machine. Histological and radiographic analyses revealed the presence of bone tissue in contact with the implant surface. A force of about 35 g was necessary to separate the implant from the bone tissue. The system proposed renders possible the study of biocompatibility in histologic terms and in terms capacity to bond to bone tissue and could be a valuable research tool and the basis for quality control of all types of material, metallic or otherwise, used in endosseous implants.

A method for the quality control of osseointegration in endosseous implants.

Metallic dental and orthopedic implants are essential therapeutic tool. The biologic success of an implant involves intimate contact between the implant and vital bone tissue, an event which has been termed osseointegration. The aim of the present study was to study the biocompatibility and biomechanic properties of different implant materials. Zircalloy 4 metallic cones (1.8 mm base x 2 mm height) were implanted in the diaphysis of the tibiae of 6 Wistar rats (90 g body weight) under i.p. Ethyl Urethane anesthesia. The animals were killed 30 days postimplantation, the tibiae were resected, and radiographed. One side chosen at random was used for the biomechanical study; whereas the other implant of each animal was processed for embedding in methyl-methacrylate. The bond of the implanted material to bone tissue was monitored immediately after resecting the tibiae by applying an extraction force to the base of the cone via a device designed ad hoc connected to a testing machine. Histological and radiographic analyses revealed the presence of bone tissue in contact with the implant surface. A force of about 35 g was necessary to separate the implant from the bone tissue. The system proposed renders possible the study of biocompatibility in histologic terms and in terms capacity to bond to bone tissue and could be a valuable research tool and the basis for quality control of all types of material, metallic or otherwise, used in endosseous implants.

A method for the quality control of osseointegration in endosseous implants

Metallic dental and orthopedic implants are essential therapeutic tool. The biologic success of an implant involves intimate contact between the implant and vital bone tissue, an event which has been termed osseointegration. The aim of the present study was to study the biocompatibility and biomechanic properties of different implant materials. Zircalloy 4 metallic cones (1.8 mm base x 2 mm height) were implanted in the diaphysis of the tibiae of 6 Wistar rats (90 g body weight) under i.p. Ethyl Urethane anesthesia. The animals were killed 30 days postimplantation, the tibiae were resected, and radiographed. One side chosen at random was used for the biomechanical study; whereas the other implant of each animal was processed for embedding in methyl-methacrylate. The bond of the implanted material to bone tissue was monitored immediately after resecting the tibiae by applying an extraction force to the base of the cone via a device designed ad hoc connected to a testing machine. Histological and radiographic analyses revealed the presence of bone tissue in contact with the implant surface. A force of about 35 g was necessary to separate the implant from the bone tissue. The system proposed renders possible the study of biocompatibility in histologic terms and in terms capacity to bond to bone tissue and could be a valuable research tool and the basis for quality control of all types of material, metallic or otherwise, used in endosseous implants.

Histomorphometry of initial bone healing around zirconium implants in rats.

Histometric evaluations as a function of time were performed with zirconium implants during the healing period in 10 Wistar rats. The implants (7 mm x 1 mm x 0.1 mm) were placed in the right tibia of the animals. Five rats were killed after 14 days and the remainder were sacrificed 30 days after implantation. The tibiae were resected, radiographed, and embedded in poly(methyl methacrylate). Three cross-sections were obtained transverse to the major axis of each tibia. Osseointegrated tissue thickness, percentage of direct bone-to-implant contact, and osseointegrated tissue volume were evaluated for each specimen. Bone formation was observed on the surface of the implanted strip that was in contact with tibia marrow. This method is proposed for the evaluation of the first stage of healing of bone in contact with different implant materials subjected to various surface treatment.