PubMed HealthSearch

Biomedical subjects

J Palau

Publications and source records attributed to J Palau.

At least 19 recordsLinked to original sources

Anatomy of a conformational transition of beta-strand 6 in soybean beta-amylase caused by substrate (or inhibitor) binding to the catalytical site.

A computational study of the five soybean beta-amylase X-ray structure reported so far revealed a peculiar conformational transition after substrate (or inhibitor) binding, which affects a segment of the beta-strand 6 (residues 341-343) in the (beta/alpha)8 molecular scaffold. Backbone distortions that involve considerable changes in the phi and psi angles were observed, as well as two sharp rotamer transitions for the Thr342 and Cys343 side chains. These changes caused the outermost CA-layer (at the C-terminal side of the barrel), which is involved in the catalysis, to shrink. Our observations strongly suggest that the 341FTC343 residue conformations in the free enzyme are not optimal for protein stability. Furthermore, as a result of conformational transitions in the ligand-binding process, there is a negative enthalpy change for these residues (-27 and -34 kcal/mol, after substrate or inhibitor binding, respectively). These findings support the proposed "stability-function" hypothesis for proteins that recognize a ligand (Shoichet BK, Baase WA, Kuroki R, Matthews BW. 1995. A relationship between protein stability and protein function. Proc Natl Acad Sci USA 92:452-456). They are also in good agreement with other experimental results in the literature that describe the role of the 341-343 segment in beta-amylase activity. Site-directed mutagenesis focused on these residues could be useful for undertaking functional studies of beta-amylase.

Binding Sites

Evolution of beta-amylase: patterns of variation and conservation in subfamily sequences in relation to parsimony mechanisms.

Soybean and sweet potato beta-amylases are structured as alpha/beta barrels and the same kind of folding may account for all known beta-amylases. We provide a comprehensive analysis of both protein and DNA (coding region) sequences of beta-amylases. The aim of the study is to contribute to the knowledge of the evolutionary molecular relationships among all known beta-amylases. Our approach combines the identification of the putative eightfold structural core formed by beta-strands with a complete multi-alignment analysis of all known sequences. Comparing putative beta-amylase (alpha/beta)8 cores from plants and microorganisms, two differentiated versions of residues at the packing sites, and a unique set of eight identical residues at the C-terminal catalytical site are observed, indicating early evolutionary divergence and absence of localized three-dimensional evolution, respectively. A new analytical approach has been developed in order to work out conserved motifs for beta-amylases, mostly related with the enzyme activity. This approach appears useful as a new routine to find sets of motifs (each set being known as a fingerprint) in protein families. We demonstrate that the evolutionary mechanism for beta-amylases is a combination of parsimonious divergence at three distinguishable rates in relation to the functional signatures, the barrel scaffold, and alpha-helix-containing loops.

Amino Acid Sequence

[Levels of cytokeratin CK19 expression in mononuclear blood cells evaluated using a reverse PCR (RT-PCR)].

AIMS: The sensitivity and specificity of a reverse transcription PCR method (RT-PCR) to detect cytokeratin K19 (CK19) expression was evaluated with the purpose of assessing its capability to detect the presence of breast cancer tumour cells in peripheral blood progenitor cell collection that had to be reinfused to breast cancer patients submitted to intensive chemotherapy as haematopoietic support. PATIENTS AND METHODS: Two breast cancers as positive samples were used and 34 samples of mononucleated blood cells as negative controls: 18 peripheral blood samples from normal subjects, 14 from different types of leukaemias (M3, M4Eo, M2, etc.) and two from two patients with Hodgkin's lymphoma. The method studied is a nested RT-PCR that amplifies the CK19 expression from the sample RNA extracted following the method of phenol-chloroform. RESULTS: The right performance of the method is demonstrated by observing the detection of CK19 transcripts in the breast cancer RNA and by obtaining good blank results both with non transcribed RNA and with DNA. Moreover, the method has an excellent sensitivity such as to allow the detection of CK19 transcripts in a 10(-6) dilution of cDNA reverse transcribed from 1 microgram of breast cancer RNA. The CK19 transcripts were also detected in the 64% of RNA obtained from the mononucleated blood cells controls, although the percentage of positivities was lower (47%) in the RNA from peripheral blood samples. Nevertheless it should be remarked that the levels of CK19 expression in the blood mononucleated cells is almost negligible since it used to extinguish at 1:5 cDNA dilution. CONCLUSIONS: The method studied is specific and has a high sensitivity that explains the detection of CK19 illegitimate expression approximately a half in mononucleated blood cells negative controls. However, the levels of CK19 expression in mononucleated blood cells were almost negligible and it used to extinguish at 1:5 cDNA dilution, therefore it could be concluded that the method might be useful to detect breast cancer occult tumours cells in mononucleated blood cell collection, always provided that a lower amount of cDNA is taken, thus decreasing to nil almost the false positive samples and keeping always a good sensitivity.

Biomarkers, Tumor

IMASIS computer-based medical record project: dealing with the human factor.

The Institut Municipal d'Assistència Sanitària (IMAS) is a health care organization in Barcelona, comprising two general hospitals, a psychiatric hospital, a surgical clinic, a geriatric center, some primary care clinics, and a research institute. Since 1984, IMAS has been engaged in creating a multicenter integrated hospital information system (IMASIS). Currently, IMASIS offers the possibility to manage administrative data, laboratory results, pathology and cytology reports, radiology reports, and pharmacy inpatient orders; it also shares this information on-line among IMAS centers. IMASIS users may also work with a word processor, a spreadsheet, a database, or a statistical package and have access to MEDLINE. A second phase of IMASIS development began in December 1993 focused on clinical information management. The goal was to move towards an integrated multimedia medical record [1]. As a first step, the implementation experiences of the most advanced hospital information systems around the world were studied. Some of these experiences detected behavioral, cultural, and organizational factors [2] as the main sources of delay, or even failure, in HIS projects. A preliminary analysis to define such factors, assess their potential impact, and introduce adequate measures to deal with them seemed unavoidable before structuring of the project. In our approach to physician attitudes analysis, two survey techniques were applied. First, every hospital service head was contacted to schedule an interview, with either a service representative or a group of staff physicians and residents. The aim was to provide detailed information about project objectives and collect personal opinions, problems encountered in the current HIS, and specific needs of every medical and surgical specialty (including imaging needs). Every service head was asked to distribute a questionnaire among all clinicians, which assessed frequency of use of IMASIS current applications, user's satisfaction level, problems to be solved in utilization of the system, errors detected in the systems' database, and the personal interest in participating in the IMASIS project. The questionnaire was also intended to be a tool to monitor IMASIS evolution. Our study showed that medical staff had a lack of information about the current HIS, leading to a poor utilization of some system options. Another major characteristic, related to the above, was the feeling that the project would negatively affect the organization of work at the hospitals. A computer-based medical record was feared to degrade physician-patient relationship, introduce supplementary administrative burden in clinicians day-to-day work, unnecessarily slow history taking, and imply too-rigid patterns of work. The most frequent problems in using the current system could be classified into two groups: problems related to lack of agility and consistency in user interface design, and those derived from lack of a common patient identification number. Duplication of medical records was the most frequent error detected by physicians. Analysis of physicians' attitudes towards IMASIS revealed a lack of confidence globally. This was probably the consequence of two current features: a lack of complete information about IMASIS possibilities and problems faced when using the system. To deal with such factors, three types of measures have been planned. First, an effort is to be done to ensure that every physician is able to adequately use the current system and understands long-term benefits of the project. This task will be better accomplished by personal interaction between clinicians and a physician from the Informatics Department than through formal teaching of IMASIS. Secondly, a protocol for evaluating the HIS is being developed and will be systematically applied to detect both database errors and systemUs design pitfalls. Finally, the IMASIS project has to find a convenient point for starting, to offer short-term re

Attitude of Health Personnel

Narrow A/T-rich zones present at the distal 5'-flanking sequences of the zein genes Zc1 and Zc2 bind a unique 30 kDa HMG-like protein.

Nuclear extracts from maize endosperm were used to investigate protein-DNA interactions in the 5'-upstream region of the Zc1 and Zc2 genes. These genes encode for zeins of apparent molecular mass (MWapp) 16 and 28 kDa, respectively, which accumulate in the endosperm during seed maturation. Binding assays revealed specific binding of a nuclear protein to three A/T-rich elements, 0.9-1.0 kbp upstream from the initiation codon. One of these elements (41 bp, 88% A/T), present in Zc1, contained a 13 nucleotide duplication. The other two (28 bp, 86% A/T; 42 bp alternating A-T) are consecutive elements in Zc2. Competition experiments strongly suggest that the three elements bind to the same protein. Protein-DNA interaction was detected in endosperm nuclear extracts of 8 to 21 days after pollination (DAP), as well as in 25 DAP embryos and in different tissues from plantlets. The protein factor has an MWapp of ca. 30 kDa. This factor has properties suggesting it is an HMG-like protein. These results are consistent with a growing accumulation of data for a number of genes indicating that A/T-rich elements, located at distal and proximal zones of the 5'-flanking sequences, interact with HMG-like proteins.

Base Composition

Rapid progression of multiple myeloma following G-CSF mobilization.

A 23-year-old man diagnosed as having multiple myeloma was treated with melphalan and prednisone monthly. After six cycles, an autologous peripheral blood stem cell transplantation (ABSCT) was planned. Peripheral blood mononuclear cells were collected after G-CSF mobilization (5 micrograms/kg/day for 5 days). Ten days after the last dose of G-CSF the patient showed a striking progression of multiple myeloma. A 57% infiltration of plasma cells in bone marrow and recurrence of laboratory abnormalities were evident. The patient's clinical course strongly suggests that myeloma progression was triggered by G-CSF and supports the concept of G-CSF mediated autocrine stimulation of myeloma growth.

Adult

[Results of endoscopic dilatation treatment of benign esophageal stenosis].

The management of benign esophageal stenoses is based on endoscopic dilatation of the tight segment for the remission of dysphagia. Five hundred and twenty sessions of dilatation with Savary-Guilliard bougies have been performed in one hundred and twenty-nine patients with benign esophageal stenoses. Patients with peptic stenoses (n = 59) needed a lesser number of sessions (mean: 2.47) than patients with postsurgical (n = 44; mean: 4.86) or caustic (n = 18; mean: 7.77) stenoses. The treatment failed in 4 patients (3.2%) and severe complications were observed in 3 patients (2.4%). These results support the efficacy and safety of this technique.

Adolescent

Helical structure of basic proteins from spermatozoa. Comparison with model peptides.

We describe structural studies carried out with some basic proteins found in association with DNA in the spermatozoa of molluscs and echinoderms. We have studied proteins related to histone H1 as well as protamines. Structural prediction methods show that these proteins have a strong helical potential and contain several turns, mainly of the SPKK type. No beta structures were found. Strong structural similarities have been detected between distantly related species. The presence of helical regions is confirmed by circular dichroism in trifluoroethanol solution. The influence of the SPKK turns is also evident in the CD spectra. In proteins which contain a high percentage of arginine we conclude that conventional prediction methods should be modified in order to allow for a higher helical potential for this amino acid residue. Synthetic peptides with a sequence present in the C-terminal region of histone H1 have also been studied. It was found that octapeptides may only acquire a small amount of structure, whereas hexadecapeptides are 50-60% helical. These studies strongly suggest that both protamines and proteins related to the C-terminal part of histone H1 interact with DNA mainly in the alpha-helical conformation.

Amino Acid Sequence

Acute myeloblastic leukemia with minimal myeloid differentiation (FAB AML-M0): a study of eleven cases.

The main clinical, morphological, cytochemical, immunological features and therapy results of eleven patients diagnosed as acute myeloblastic leukemia M0 (AML-M0) are reported here. There were no clinical characteristics, abnormalities on physical examination or initial laboratory parameters that distinguished these eleven patients. Bone marrow aspirates were hypocellular in four patients. The leukemic cells were undifferentiated by light microscopy and myeloperoxidase (MPO) and/or Sudan Black B (SBB) stains were negative in all cases. Myeloid differentiation antigens were present on the leukemic cells of all eleven patients, whereas B and T cell markers were clearly negative except for CD4 and CD7 antigens. Whatever the treatment employed survival was very short. Eight of the eleven patients were treated and two achieved complete remission (CR) but only one of them is alive in continuous CR. Our results like those previously reported, suggest that AML-M0 patients have a very poor prognosis with standard induction therapies and should perhaps be considered for experimental therapeutic approaches.

Adolescent

[Clinical profile and course of paroxysmal nocturnal hemoglobinuria].

PURPOSE: To evaluate the clinical characteristics, laboratory findings, course, treatment and survival of a series of patients with PNH. PATIENTS AND METHODS: The clinical records of 21 patients diagnosed of PNH in the La Fe University Hospital between 1970 and July 1991 were revised. Positivity to Ham's and sucrose tests was the major diagnostic criterion. Haemolysis was studied by means of reticulocyte count, unconjugated bilirubin, LDH levels, haptoglobin, serum iron, and haemosiderinuria. The survival analysis was performed in accordance with Kaplan and Meier. RESULTS: The median age in the group was 38 years (range: 18-72 years) and the M/F ratio was 11/10. The commonest symptoms at onset were weakness (76%), dark urine (47%), jaundice (33%), and purpura (24%). All the patients had anaemia, six of them (28%) presenting with aplastic anaemia. The complications most frequently seen included thrombosis (documented in 7 cases, clinically suspected in 6 others), infection (6 cases) and haemorrhage (6 cases). One patient developed aplastic anaemia after 16 years of follow-up, and another one had AML. None of the patients with PNH-associated aplastic anaemia developed thrombosis. The incidence of severe cytopenia was: Hb < 80 g/L, 62%; platelet count < or = 20 x 10(9)/L, 29%, and white cell count < or = 2 x 10(9)/L, 14%. The haemolysis-related findings were as follows: unconjugated hyperbilirubinemia, 100%; haemosiderinuria, 87%; decreased haptoglobin, 80%. Transfusion support consisted of washed red cells (total amount, 1,684 units) and platelets (137 units). A female patient with anticoagulant therapy developed haemolysis after non-isogroup plasma transfusion. Five patients required no transfusions. One patient was subjected to splenectomy and other underwent a successful bone-marrow transplant. The cause of death was related to PNH in three of the five patients who had died when this study was finished (mesenteric thrombosis, subcapsular haematoma of the liver and AML). The actuarial survival at 10 years was 68%. CONCLUSIONS: 1) The incidence of PNH is very low in our experience, excessive delay in diagnosis being the rule, as in other reported series. 2) Early anti-thrombotic treatment should be carried out in PNH whenever severe thrombocytopenia is not associated. 3) Allogeneic BMT is the only curative treatment.

Adolescent

Carboplatin alone or in combination in high-risk acute nonlymphoblastic leukemia.

The use of newly developed antileukemic agents is one of the therapeutic options available to overcome clinical resistance in refractory or other high-risk acute leukemias. Carboplatin is a second-generation platinum compound that has demonstrated significant activity against acute leukemia, particularly when administered via continuous intravenous infusion in phase I clinical trials. Based on the preliminary reports of these trials, we designed a phase II clinical trial to evaluate the efficacy and toxicity of carboplatin via continuous infusion (300 mg/m2/d for 5 days) for remission induction in adult patients with high-risk acute leukemia. Because of the significant antileukemic activity and the scarce extrahematologic toxicity noted in this trial, in order to increase the response rate, we were encouraged to try carboplatin in combination in a similar set of patients. A phase II study of carboplatin 300 mg/m2/d for 5 days in combination with etoposide 100 mg/m2/d for 3 to 4 days was designed by our group to treat patients with high-risk acute leukemia. This combination was chosen because (1) each drug has independent activity in acute nonlymphoblastic leukemia (ANLL) and (2) carboplatin/etoposide has been extensively tested in patients with small and non-small cell lung cancer, and therefore the toxicity and maximum tolerated dose are known. The complete remission rate achieved was somewhat higher (40%) than with carboplatin alone despite the increased incidence of extrahematologic toxicities, particularly gastrointestinal bleeding. At present, carboplatin should be considered as a new effective agent for the treatment of ANLL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent

Anti-Sm sera are misdetected by counterimmunoelectrophoresis. A critical analysis of CIE and western blotting on the detection of human antinuclear antibodies.

The ability of CIE and Western blotting to detect antibodies against the Sm, RNP and SS/B antigens was tested in 84 sera from SLE patients. CIE and Western blotting gave identical results for anti-RNP and anti-SS/B; positivity was detected in the same sera regardless of the technique used and no new positive sera were found by Western blotting among those classified by CIE as not showing immunological relationship to the anti-RNP and anti-SS/B references. CIE detected only half of the anti-Sm that were positive by Western blotting. The inability of CIE to detect sera positive for anti-Sm could not be ascribed to specific features of the sera, such as low titer or the lack of antibodies to the Sm antigens B/B' and/or D. The identity of a number of these new anti-Sm sera was confirmed by the utilization of an in vitro translation test, where the 'cell-free' translation products were immunoprecipitated with the new positive anti-Sm sera.

Antibodies, Antinuclear

The b-32 protein from maize endosperm: characterization of genomic sequences encoding two alternative central domains.

As derived from a cDNA clone, the structure of the b-32 protein of Zea mays, a putative regulatory factor of zein expression, has a central acidic region separated by two domains covered by secondary structure motifs. In this work, three b-32 genomic clones were selected from two genomic libraries obtained from the maize inbred lines W64A and A69Y. The nucleotide sequences of the complete coding region of each b-32 gene, as well as long stretches of their 5' and 3' flanking regions, were determined. Introns are not present in the b-32 genomic sequences. Minor variations among the three genes and an earlier reported b-32 cDNA indicates that they constitute a gene family showing a characteristic polymorphism. Such a polymorphism is highly evident in large segments of the upstream regulatory sequences. Interestingly, when compared with cDNA (W64A) or with gene b-32.120 (W64A), the genes b-32.129 (W64A) and b-32.152 (A69Y) show three jumps of the reading frame in the central part of the coding region, resulting in a completely different sequence of the b-32 protein central domain. In all cases, variations in the N- and C-terminal domains account only for microheterogeneity.

Amino Acid Sequence