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1.
Anal Bioanal Chem ; 407(22): 6771-80, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26123440

RESUMO

The metabolic composition and concentration knowledge provided by magnetic resonance spectroscopy (MRS) liquid and high-resolution magic angle spinning spectroscopy (HR-MAS) has a relevant impact in clinical practice during magnetic resonance imaging (MRI) monitoring of human tumors. In addition, the combination of morphological and chemical information by MRI and MRS has been particularly useful for diagnosis and prognosis of tumor evolution. MRI spatial resolution reachable in human beings is limited for safety reasons and the demanding necessary conditions are only applicable on experimental model animals. Nevertheless, MRS and MRI can be performed on human biopsies at high spatial resolution, enough to allow a direct correlation between the chemical information and the histological features observed in such biopsies. Although HR-MAS is nowadays a well-established technique for spectroscopic analysis of tumor biopsies, with this approach just a mean metabolic profile of the whole sample can be obtained and thus the high histological heterogeneity of some important tumors is mostly neglected. The value of metabolic HR-MAS data strongly depends on a wide statistical analysis and usually the microanatomical rationale for the correlation between histology and spectroscopy is lost. We present here a different approach for the combined use of MRI and MRS on fresh human brain tumor biopsies with native contrast. This approach has been designed to achieve high spatial (18 × 18 × 50 µm) and spectral (0.031 µL) resolution in order to obtain as much spatially detailed morphological and metabolical information as possible without any previous treatment that can alter the sample. The preservation of native tissue conditions can provide information that can be translated to in vivo studies and additionally opens the possibility of performing other techniques to obtain complementary information from the same sample.


Assuntos
Biomarcadores Tumorais/metabolismo , Neoplasias Encefálicas/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Algoritmos , Humanos , Aumento da Imagem/métodos , Técnicas In Vitro , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Distribuição Tecidual
2.
Antioxidants (Basel) ; 13(5)2024 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-38790644

RESUMO

Oxidative stress forms part of the molecular basis contributing to the development and manifestation of myopia, a refractive error with associated pathology that is increasingly prevalent worldwide and that subsequently leads to an upsurge in degenerative visual impairment due to conditions that are especially associated with high myopia. The purpose of our study was to examine the interrelation of potential oxidative-stress-related metabolites found in the aqueous humor of high-myopic, low-myopic, and non-myopic patients within a clinical study. We conducted a cross-sectional study, selecting two sets of patients undergoing cataract surgery. The first set, which was used to analyze metabolites through an NMR assay, comprised 116 patients. A total of 59 metabolites were assigned and quantified. The PLS-DA score plot clearly showed a separation with minimal overlap between the HM and control samples. The PLS-DA model allowed us to determine 31 major metabolite differences in the aqueous humor of the study groups. Complementary statistical analysis of the data allowed us to determine six metabolites that presented significant differences among the experimental groups (p < 005). A significant number of these metabolites were discovered to have a direct or indirect connection to oxidative stress linked with conditions of myopic eyes. Notably, we identified metabolites associated with bioenergetic pathways and metabolites that have undergone methylation, along with choline and its derivatives. The second set consisted of 73 patients who underwent a glutathione assay. Here, we showed significant variations in both reduced and oxidized glutathione in aqueous humor among all patient groups (p < 0.01) for the first time. Axial length, refractive status, and complete ophthalmologic examination were also recorded, and interrelations among metabolic and clinical parameters were evaluated.

3.
Anal Bioanal Chem ; 403(9): 2611-25, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22552786

RESUMO

Quantitative multinuclear high-resolution magic angle spinning was performed in order to determine the tissue pH values of and the absolute metabolite concentrations in 33 samples of human brain tumour tissue. Metabolite concentrations were quantified by 1D (1)H and (31)P HRMAS using the electronic reference to in vivo concentrations (ERETIC) synthetic signal. (1)H-(1)H homonuclear and (1)H-(31)P heteronuclear correlation experiments enabled the direct assessment of the (1)H-(31)P spin systems for signals that suffered from overlapping in the 1D (1)H spectra, and linked the information present in the 1D (1)H and (31)P spectra. Afterwards, the main histological features were determined, and high heterogeneity in the tumour content, necrotic content and nonaffected tissue content was observed. The metabolite profiles obtained by HRMAS showed characteristics typical of tumour tissues: rather low levels of energetic molecules and increased concentrations of protective metabolites. Nevertheless, these characteristics were more strongly correlated with the total amount of living tissue than with the tumour cell contents of the samples alone, which could indicate that the sampling conditions make a significant contribution aside from the effect of tumour development in vivo. The use of methylene diphosphonic acid as a chemical shift and concentration reference for the (31)P HRMAS spectra of tissues presented important drawbacks due to its interaction with the tissue. Moreover, the pH data obtained from (31)P HRMAS enabled us to establish a correlation between the pH and the distance between the N(CH(3))(3) signals of phosphocholine and choline in (1)H spectra of the tissue in these tumour samples.


Assuntos
Biomarcadores Tumorais/metabolismo , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Encéfalo/metabolismo , Encéfalo/patologia , Espectroscopia de Ressonância Magnética/métodos , Biomarcadores Tumorais/análise , Humanos , Hidrogênio/análise , Hidrogênio/metabolismo , Isótopos de Fósforo/análise , Isótopos de Fósforo/metabolismo
4.
Artigo em Inglês | MEDLINE | ID: mdl-20871822

RESUMO

HRMAS NMR is considered a valuable technique to obtain detailed metabolic profile of unprocessed tissues. To properly interpret the HRMAS metabolomic results, detailed information of the actual state of the sample inside the rotor is needed. MRM (Magnetic Resonance Microscopy) was applied for obtaining structural and spatially localized metabolic information of the samples inside the HRMAS rotors. The tissue was observed stuck to the rotor wall under the effect of HRMAS spinning. MRM spectroscopy showed a transference of metabolites from the tissue to the medium. The sample shape and the metabolite transfer after HRMAS indicated that tissue had undergone alterations and it can not be strictly considered as intact. This must be considered when HRMAS is used for metabolic tissue characterization, and it is expected to be highly dependent on the manipulation of the sample. The localized spectroscopic information of MRM reveals the biochemical compartmentalization on tissue samples hidden in the HRMAS spectrum.


Assuntos
Neoplasias Encefálicas/metabolismo , Glioma/metabolismo , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Metaboloma , Proteoma/metabolismo , Neoplasias Encefálicas/patologia , Glioma/patologia , Humanos , Marcadores de Spin , Distribuição Tecidual , Células Tumorais Cultivadas
5.
J Neurooncol ; 103(1): 71-85, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-20820872

RESUMO

Malignant gliomas are the most common subtype of primary central nervous system (CNS) tumors. Their pathological classification, however, remains subjective, stimulating researchers to actively seek objective molecular markers to discover alternative and more reproducible tools for improved subtypification. Herein, we present a global survey of genomic alterations in oligodendroglial tumors (OT). Genetic and epigenetic alterations identified in this study are correlated with OT molecular groups we have recently reported: a neurogenic group composed of tumors with loss of heterozygosity (LOH) at 1p-19q, IDH1 mutations, and MGMT promoter methylation, showing good prognosis; an intermediate group, presenting TP53 mutations or LOH at 17p, IDH1 mutations, and GSTP1 promoter methylation; and a proliferative group, presenting major genetic alterations (LOH at 10q, EGFR amplification, and CDKN2A/ARF deletion) and poor prognosis. These results allowed us to refine our molecular characterization associated with prognosis, referring exclusively to oligodendroglial tumors.


Assuntos
Desequilíbrio Alélico , Neoplasias Encefálicas/genética , Perfilação da Expressão Gênica , Genoma Humano , Oligodendroglioma/genética , Adolescente , Adulto , Idoso , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Western Blotting , Pré-Escolar , Cromossomos Humanos/genética , Metilação de DNA , Epigenômica , Humanos , Perda de Heterozigosidade , Pessoa de Meia-Idade , Mutação/genética , Análise de Sequência com Séries de Oligonucleotídeos , Polimorfismo de Nucleotídeo Único/genética , Prognóstico , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Taxa de Sobrevida
6.
J Biomed Inform ; 44(4): 677-87, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21377545

RESUMO

In the last decade, machine learning (ML) techniques have been used for developing classifiers for automatic brain tumour diagnosis. However, the development of these ML models rely on a unique training set and learning stops once this set has been processed. Training these classifiers requires a representative amount of data, but the gathering, preprocess, and validation of samples is expensive and time-consuming. Therefore, for a classical, non-incremental approach to ML, it is necessary to wait long enough to collect all the required data. In contrast, an incremental learning approach may allow us to build an initial classifier with a smaller number of samples and update it incrementally when new data are collected. In this study, an incremental learning algorithm for Gaussian Discriminant Analysis (iGDA) based on the Graybill and Deal weighted combination of estimators is introduced. Each time a new set of data becomes available, a new estimation is carried out and a combination with a previous estimation is performed. iGDA does not require access to the previously used data and is able to include new classes that were not in the original analysis, thus allowing the customization of the models to the distribution of data at a particular clinical center. An evaluation using five benchmark databases has been used to evaluate the behaviour of the iGDA algorithm in terms of stability-plasticity, class inclusion and order effect. Finally, the iGDA algorithm has been applied to automatic brain tumour classification with magnetic resonance spectroscopy, and compared with two state-of-the-art incremental algorithms. The empirical results obtained show the ability of the algorithm to learn in an incremental fashion, improving the performance of the models when new information is available, and converging in the course of time. Furthermore, the algorithm shows a negligible instance and concept order effect, avoiding the bias that such effects could introduce.


Assuntos
Algoritmos , Inteligência Artificial , Neoplasias Encefálicas/diagnóstico , Biologia Computacional/métodos , Análise Discriminante , Bases de Dados Factuais , Humanos , Imageamento por Ressonância Magnética
7.
MAGMA ; 24(1): 35-42, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21249420

RESUMO

OBJECT: This study demonstrates that 3T SV-MRS data can be used with the currently available automatic brain tumour diagnostic classifiers which were trained on databases of 1.5T spectra. This will allow the existing large databases of 1.5T MRS data to be used for diagnostic classification of 3T spectra, and perhaps also the combination of 1.5T and 3T databases. MATERIALS AND METHODS: Brain tumour classifiers trained with 154 1.5T spectra to discriminate among high grade malignant tumours and common grade II glial tumours were evaluated with a subsequently-acquired set of 155 1.5T and 37 3T spectra. A similarity study between spectra and main brain tumour metabolite ratios for both field strengths (1.5T and 3T) was also performed. RESULTS: Our results showed that classifiers trained with 1.5T samples had similar accuracy for both test datasets (0.87 ± 0.03 for 1.5T and 0.88 ± 0.03 for 3.0T). Moreover, non-significant differences were observed with most metabolite ratios and spectral patterns. CONCLUSION: These results encourage the use of existing classifiers based on 1.5T datasets for diagnosis with 3T (1)H SV-MRS. The large 1.5T databases compiled throughout many years and the prediction models based on 1.5T acquisitions can therefore continue to be used with data from the new 3T instruments.


Assuntos
Neoplasias Encefálicas/diagnóstico , Bases de Dados Factuais , Espectroscopia de Ressonância Magnética/métodos , Reconhecimento Automatizado de Padrão/métodos , Neoplasias Encefálicas/metabolismo , Humanos , Prótons , Sensibilidade e Especificidade
8.
Eur Radiol Exp ; 5(1): 56, 2021 12 29.
Artigo em Inglês | MEDLINE | ID: mdl-34966953

RESUMO

BACKGROUND: Indirect 1H-magnetic resonance (MR) imaging of 17O-labelled water allows imaging in vivo dynamic changes in water compartmentalisation. Our aim was to describe the feasibility of indirect 1H-MR methods to evaluate the effect of H217O on the MR relaxation rates by using conventional a 3-T equipment and voxel-wise relaxation rates. METHODS: MR images were used to calculate the R1, R2, and R2* relaxation rates in phantoms (19 vials with different H217O concentrations, ranging from 0.039 to 5.5%). Afterwards, an experimental animal pilot study (8 rats) was designed to evaluate the in vivo relative R2 brain dynamic changes related to the intravenous administration of 17O-labelled water in rats. RESULTS: There were no significant changes on the R1 and R2* values from phantoms. The R2 obtained with the turbo spin-echo T2-weighted sequence with 20-ms echo time interval had the higher statistical difference (0.67 s-1, interquartile range 0.34, p < 0.001) and Spearman correlation (rho 0.79). The R2 increase was adjusted to a linear fit between 0.25 and 5.5%, represented with equation R2 = 0.405 concentration + 0.3215. The highest significant differences were obtained for the higher concentrations (3.1-5.5%). The rat brain MR experiment showed a mean 10% change in the R2 value after the H217O injection with progressive normalisation. CONCLUSIONS: Indirect 1H-MR imaging method is able to measure H217O concentration by using R2 values and conventional 3-T MR equipment. Normalised R2 relative dynamic changes after the intravenous injection of a H217O saline solution provide a unique opportunity to map water pathophysiology in vivo, opening the analysis of aquaporins status and modifications by disease at clinically available 3-T proton MR scanners.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Animais , Encéfalo/diagnóstico por imagem , Estudos de Viabilidade , Imagens de Fantasmas , Projetos Piloto , Ratos
9.
Mod Pathol ; 23(6): 856-65, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20305620

RESUMO

Gene amplification is a process that is characterized by an increase in the copy number of a restricted region in a chromosome arm, and is frequently associated with an overexpression of the corresponding amplified gene. Amplified DNA can be organized either as extrachromosomal elements, repeated units at a single locus or scattered throughout the genome. The amplification of the gene for epidermal growth factor receptor (EGFR) is a common finding in glioblastomas and the amplified gene copies appears as double minutes. The aim of this study was to investigate the different patterns of EGFR amplification in 40 cases of glioblastoma using FISH analysis in metaphases and paraffin sections, and to investigate the relationship of gene copy number with gene expression profile. The analysis of copy number alterations of EGFR was validated by quantitative PCR and SNP microarrays. We observed that in 42% of the cases, the type of amplification of EGFR was as double minute chromosomes. In addition, we detected another type of amplification, with extra copies of EGFR inserted in different loci of chromosome 7, present in 28% of cases. In this form of amplification, the number of copies is small, and the percentage of cells with EGFR amplification is rarely more than 15%. This model of amplification could correspond to a variant of the insertion mechanism, or a consequence of a process of duplication. Our results suggest that this mechanism could represent an early stage of amplification in glioblastomas. Overall, we found a close correlation between EGFR gene copy-number alterations and the level of EGFR protein expression. However, all cases with a high level of mRNA exhibited strong expression for the EGFR protein, and most cases with a low level of mRNA showed no overexpression of EGFR protein.


Assuntos
Neoplasias Encefálicas/genética , Cromossomos Humanos Par 7 , Receptores ErbB/genética , Amplificação de Genes , Dosagem de Genes , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Glioblastoma/genética , Adulto , Idoso , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Receptores ErbB/metabolismo , Feminino , Perfilação da Expressão Gênica/métodos , Glioblastoma/metabolismo , Glioblastoma/patologia , Humanos , Imuno-Histoquímica , Hibridização in Situ Fluorescente , Masculino , Pessoa de Meia-Idade , Mutagênese Insercional , Análise de Sequência com Séries de Oligonucleotídeos , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/metabolismo , Células Tumorais Cultivadas , Adulto Jovem
10.
NMR Biomed ; 23(5): 485-95, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20336675

RESUMO

The environment of the oocyte during its in vivo maturation consists of follicular fluid (FF) and is surrounded by granulosa cells. The FF is derived from the sanguineous plasma and secretions, synthesised in the follicle wall, that contain a large variety of growth factors, cytokines, amino acids, and other metabolites. These metabolites are presumably involved in the physiology of the oocyte. The identification, quantification and study of FF metabolites can provide additional information about the oocyte state which can be helpful in distinguishing those oocytes that have a greater capacity to be fertilised and to develop properly. The aim of this work is to identify the metabolic profile of FF samples exhaustively using High Resolution Nuclear Magnetic Resonance (NMR). A total of 30 FF samples from oocyte donors (<35 years) were analysed. Different monodimensional (1D) and bidimensional (2D) (homo and heteronuclear) NMR experiments were acquired. A total of 131 chemical shifts were assigned and 42 metabolites, including as example glucose, lactate, acetate, acetoacetate, pyruvate and beta-hydroxybutyrate, were identified. High correlations were found between these important intermediaries of the energetic metabolic pathways of the follicle which can indicate the importance of these pathways in oocyte development. Some of these identified metabolites might be useful as biomarkers of the follicular maturation state, allowing oocytes with a higher fertilisation potential to be selected, thereby increasing pregnancy rates in women following in vitro fertilisation (IVF) treatments.


Assuntos
Líquido Folicular/metabolismo , Metaboloma , Adolescente , Adulto , Feminino , Humanos , Espectroscopia de Ressonância Magnética , Redes e Vias Metabólicas , Doadores de Tecidos , Adulto Jovem
11.
J Neurooncol ; 95(3): 343-354, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19597701

RESUMO

Oligodendroglial tumors presenting loss of heterozygosity (LOH) at 1p and 19q have been shown to be sensitive to chemotherapy, thus making 1p-19q status testing a key aspect in oligodendroglioma diagnosis and prognosis. Twenty-nine tumor samples (19 oligodendrogliomas, 10 oligoastrocytomas) were analyzed in order to obtain a molecular profile identifying those bearing 1p-19q LOH. Other genomic anomalies usually present in gliomas, such as EGFR amplification, CDKN2A/ARF deletion, 10q LOH and TP53 mutation, were also studied. Tumors with 1p-19q LOH overexpressed genes related to neurogenesis. Genes linked to immune response, proliferation and inflammation were overexpressed in the group with intact 1p-19q; this group could in turn be further divided in two subgroups: one overexpressing genes involved in immune response and inflammation that did not show major genetic aberrations other than the TP53 mutation and EGFR trisomy in a few cases, and another overexpressing genes related to immune response and proliferation that had a predominance of samples carrying several anomalies and presenting worse outcomes. This molecular signature was validated by analyzing a set of ten tumor samples (three oligodendrogliomas, seven oligoastrocytomas); all ten samples were correctly assigned. LOH at 1p-19q results in haploinsufficiency and copy number reduction of several genes, including NOTCH 2; this phenomenon produces a global change in gene expression inducing a pro-neural status that results in restrictions to cell migration and proliferation. Tumors without LOH at 1p-19q exhibit the opposite characteristics, explaining their more aggressive behavior.


Assuntos
Neoplasias Encefálicas/genética , Cromossomos Humanos Par 19 , Cromossomos Humanos Par 1 , Regulação Neoplásica da Expressão Gênica , Perda de Heterozigosidade , Oligodendroglioma/genética , Adolescente , Adulto , Idoso , Pré-Escolar , Deleção Cromossômica , Análise por Conglomerados , Perfilação da Expressão Gênica , Humanos , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase Via Transcriptase Reversa
12.
MAGMA ; 22(1): 5-18, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18989714

RESUMO

JUSTIFICATION: Automatic brain tumor classification by MRS has been under development for more than a decade. Nonetheless, to our knowledge, there are no published evaluations of predictive models with unseen cases that are subsequently acquired in different centers. The multicenter eTUMOUR project (2004-2009), which builds upon previous expertise from the INTERPRET project (2000-2002) has allowed such an evaluation to take place. MATERIALS AND METHODS: A total of 253 pairwise classifiers for glioblastoma, meningioma, metastasis, and low-grade glial diagnosis were inferred based on 211 SV short TE INTERPRET MR spectra obtained at 1.5 T (PRESS or STEAM, 20-32 ms) and automatically pre-processed. Afterwards, the classifiers were tested with 97 spectra, which were subsequently compiled during eTUMOUR. RESULTS: In our results based on subsequently acquired spectra, accuracies of around 90% were achieved for most of the pairwise discrimination problems. The exception was for the glioblastoma versus metastasis discrimination, which was below 78%. A more clear definition of metastases may be obtained by other approaches, such as MRSI + MRI. CONCLUSIONS: The prediction of the tumor type of in-vivo MRS is possible using classifiers developed from previously acquired data, in different hospitals with different instrumentation under the same acquisition protocols. This methodology may find application for assisting in the diagnosis of new brain tumor cases and for the quality control of multicenter MRS databases.


Assuntos
Inteligência Artificial , Biomarcadores Tumorais/análise , Neoplasias Encefálicas/classificação , Neoplasias Encefálicas/metabolismo , Diagnóstico por Computador/métodos , Espectroscopia de Ressonância Magnética/métodos , Reconhecimento Automatizado de Padrão/métodos , Algoritmos , Neoplasias Encefálicas/diagnóstico , Europa (Continente) , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
13.
Proteins ; 66(3): 726-39, 2007 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-17143896

RESUMO

The Escherichia coli MnmE protein is a 50-kDa multidomain GTPase involved in tRNA modification. Its homologues in eukaryotes are crucial for mitochondrial respiration and, thus, it is thought that the human protein might be involved in mitochondrial diseases. Unlike Ras, MnmE shows a high intrinsic GTPase activity and requires effective GTP hydrolysis, and not simply GTP binding, to be functionally active. The isolated MnmE G-domain (165 residues) conserves the GTPase activity of the entire protein, suggesting that it contains the catalytic residues for GTP hydrolysis. To explore the GTP hydrolysis mechanism of MnmE, we analyzed the effect of low pH on binding and hydrolysis of GTP, as well as on the formation of a MnmE transition state mimic. GTP hydrolysis by MnmE, but not GTP binding or formation of a complex with mant-GDP and aluminium fluoride, is impaired at acidic pH, suggesting that the chemistry of the transition state mimic is different to that of the true transition state, and that some residue(s), critical for GTP hydrolysis, is severely affected by low pH. We use a nuclear magnetic resonance (NMR)-based approach to get insights into the MnmE structure and properties. The combined use of NMR restraints and homology structural information allowed the determination of the MnmE G-domain structure in its free form. Chemical shift structure-based prediction provided a good basis for structure refinement and validation. Our data support that MnmE, unlike other GTPases, does not use an arginine finger to drive catalysis, although Arg252 may play a role in stabilization of the transition state.


Assuntos
Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Escherichia coli/enzimologia , GTP Fosfo-Hidrolases/química , GTP Fosfo-Hidrolases/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Proteínas de Escherichia coli/genética , GTP Fosfo-Hidrolases/genética , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Cinética , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Dados de Sequência Molecular , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos
14.
Biochem J ; 387(Pt 1): 57-66, 2005 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-15535803

RESUMO

Echistatin is a potent antagonist of the integrins alpha(v)beta3, alpha5beta1 and alpha(IIb)beta3. Its full inhibitory activity depends on an RGD (Arg-Gly-Asp) motif expressed at the tip of the integrin-binding loop and on its C-terminal tail. Previous NMR structures of echistatin showed a poorly defined integrin-recognition sequence and an incomplete C-terminal tail, which left the molecular basis of the functional synergy between the RGD loop and the C-terminal region unresolved. We report a high-resolution structure of echistatin and an analysis of its internal motions by off-resonance ROESY (rotating-frame Overhauser enhancement spectroscopy). The full-length C-terminal polypeptide is visible as a beta-hairpin running parallel to the RGD loop and exposing at the tip residues Pro43, His44 and Lys45. The side chains of the amino acids of the RGD motif have well-defined conformations. The integrin-binding loop displays an overall movement with maximal amplitude of 30 degrees . Internal angular motions in the 100-300 ps timescale indicate increased flexibility for the backbone atoms at the base of the integrin-recognition loop. In addition, backbone atoms of the amino acids Ala23 (flanking the R24GD26 tripeptide) and Asp26 of the integrin-binding motif showed increased angular mobility, suggesting the existence of major and minor hinge effects at the base and the tip, respectively, of the RGD loop. A strong network of NOEs (nuclear Overhauser effects) between residues of the RGD loop and the C-terminal tail indicate concerted motions between these two functional regions. A full-length echistatin-alpha(v)beta3 docking model suggests that echistatin's C-terminal amino acids may contact alpha(v)-subunit residues and provides new insights to delineate structure-function correlations.


Assuntos
Ressonância Magnética Nuclear Biomolecular/métodos , Peptídeos/química , Peptídeos/metabolismo , Animais , Sítios de Ligação/fisiologia , Peptídeos e Proteínas de Sinalização Intercelular , Ligação Proteica/fisiologia , Conformação Proteica , Estrutura Terciária de Proteína , Serpentes
15.
Stud Health Technol Inform ; 120: 82-92, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16823125

RESUMO

The analysis of the angiogenesis in hepatic lesions is an important marker of tumour aggressiveness and response to therapy. However, the quantitative analysis of this fact requires a deep knowledge of the hepatic perfusion. The development of pharmacokinetic models constitutes a very valuable tool, but it is computationally intensive. Moreover, abdominal imaging processing increases the computational requirements since the movement of the patient makes images in a time series incomparable, requiring a previous pre-processing. This work presents a Grid environment developed to deal with the computational demand of pharmacokinetic modelling. This article proposes and implements a four-level software architecture that provides a simple interface to the user and deals transparently with the complexity of Grid environment. The four layers implemented are: Grid Layer (the closest to the Grid infrastructure), the Gate-to- Grid (which transforms the user requests to Grid operations), the Web Services layer (which provides a simple, standard and ubiquitous interface to the user) and the Application Layer. An application has been developed on top of this architecture to manage the execution of multi-parametric groups of co-registration actions on a large set of medical images. The execution has been performed on the EGEE Grid infrastructure. The application is platform-independent and can be used from any computer without special requirements.


Assuntos
Simulação por Computador , Meios de Contraste/farmacocinética , Imageamento por Ressonância Magnética , Farmacocinética , Software , Meios de Contraste/administração & dosagem , Humanos
16.
J Mol Biol ; 329(1): 135-45, 2003 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-12742023

RESUMO

The solution structure of obtustatin, a novel non-RGD disintegrin of 41 residues isolated from Vipera lebetina obtusa venom, and a potent and selective inhibitor of the adhesion of integrin alpha(1)beta(1) to collagen IV, has been determined by two-dimensional nuclear magnetic resonance. Almost the whole set of chemical shifts for 1H, 13C and 15N were assigned at natural abundance from 2D homonuclear and heteronuclear 500 MHz, 600 MHz and 800 MHz spectra at pH 3.0 recorded at 298 K and 303 K. Final structural constraints consisted of 302 non-redundant NOE (95 long-range, 60 medium, 91 sequential and 56 intra-residue), four disulfide bond distances, five chi1 dihedral angles and four hydrogen bonds. The 20 conformers with lowest total energy had no NOE violations greater than 0.35A or dihedral angle violations greater than 12 degrees. The average root-mean-square deviation (RMSD) for backbone atoms of all residues among the 20 conformers was 1.1A and 0.6A for the 29 best-defined residues. Obtustatin lacks any secondary structure. Compared to all known disintegrin structures in which the RGD motif is located at the apex of an 11 residue hairpin loop, the active KTS tripeptide of obtustatin is oriented towards a side of its nine residue integrin-binding loop. The C-terminal tail is near to the active loop, and these two structural elements display the largest atomic displacements due to local conformational disorder. Double cross-peaks for W20, Y28 and H27 in the aromatic region of TOCSY spectra, local RMSD values for these residues, and positive cross-peaks in a ROESY spectrum (600 MHz, 100 ms mixing time), suggest that these residues act as a hinge allowing for the overall flexibility of the entire integrin-binding loop. These distinct structural features, along with its different electrostatic surface potential in relation to other known disintegrins, may confer to obtustatin its reported alpha(1)beta(1) integrin inhibitory selectivity.


Assuntos
Desintegrinas/química , Ressonância Magnética Nuclear Biomolecular/métodos , Venenos de Víboras/química , Sequência de Aminoácidos , Animais , Dicroísmo Circular , Cristalografia por Raios X/métodos , Desintegrinas/metabolismo , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Modelos Moleculares , Dados de Sequência Molecular , Estrutura Molecular , Oligopeptídeos/química , Conformação Proteica , Homologia de Sequência de Aminoácidos , Soluções , Eletricidade Estática , Venenos de Víboras/metabolismo
17.
Toxicon ; 45(8): 1063-74, 2005 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-15922775

RESUMO

Disintegrins represent a family of polypeptides present in the venoms of various vipers that selectively block the function of integrin receptors. Here, we review our current view and hypothesis on the emergence and the structural and functional diversification of disintegrins by accelerated evolution and the selective loss of disulfide bonds of duplicated genes. Research on disintegrins is relevant for understanding the biology of viper venom toxins, but also provides information on new structural determinants involved in integrin recognition that may be useful in basic and clinical research. The role of the composition, conformation, and dynamics of the integrin inhibitory loop acting in concert with the C-terminal tail in determining the selective inhibition of integrin receptors is discussed.


Assuntos
Desintegrinas/química , Desintegrinas/genética , Evolução Molecular , Modelos Moleculares , Venenos de Serpentes/metabolismo , Serpentes , Motivos de Aminoácidos/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Desintegrinas/classificação , Genes Duplicados , Integrinas/metabolismo , Dados de Sequência Molecular , Filogenia , Estrutura Terciária de Proteína , Alinhamento de Sequência , Relação Estrutura-Atividade
18.
Protein Sci ; 12(2): 366-71, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12538900

RESUMO

Disintegrins represent a group of cysteine-rich peptides occurring in Crotalidae and Viperidae snake venoms, and are potent antagonists of several integrin receptors. A novel disintegrin, obtustatin, was isolated from the venom of the Vipera lebetina obtusa viper, and represents the first potent and selective inhibitor of the binding of integrin alpha(1)beta(1) to collagen IV. The primary structure of obtustatin contains 41 amino acids and is the shortest disintegrin described to date. Obtustatin shares the pattern of cysteines of other short disintegrins. However, in contrast to known short disintegrins, the integrin-binding loop of obtustatin is two residues shorter and does not express the classical RGD sequence. Using synthetic peptides, a KTS motif was identified as the integrin-binding sequence. A three-dimensional model of obtustatin, built by homology-modeling structure calculations using different templates and alignments, strongly indicates that the novel KTS motif may reside at the tip of a flexible loop.


Assuntos
Desintegrinas/química , Desintegrinas/isolamento & purificação , Venenos de Víboras/química , Venenos de Víboras/isolamento & purificação , Viperidae , Sequência de Aminoácidos , Animais , Modelos Moleculares , Dados de Sequência Molecular , Oligopeptídeos
20.
Biomicrofluidics ; 8(6): 064105, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25553182

RESUMO

A new microfluidic cell culture device compatible with real-time nuclear magnetic resonance (NMR) is presented here. The intended application is the long-term monitoring of 3D cell cultures by several techniques. The system has been designed to fit inside commercially available NMR equipment to obtain maximum readout resolution when working with small samples. Moreover, the microfluidic device integrates a fibre-optic-based sensor to monitor parameters such as oxygen, pH, or temperature during NMR monitoring, and it also allows the use of optical microscopy techniques such as confocal fluorescence microscopy. This manuscript reports the initial trials culturing neurospheres inside the microchamber of this device and the preliminary images and spatially localised spectra obtained by NMR. The images show the presence of a necrotic area in the interior of the neurospheres, as is frequently observed in histological preparations; this phenomenon appears whenever the distance between the cells and fresh nutrients impairs the diffusion of oxygen. Moreover, the spectra acquired in a volume of 8 nl inside the neurosphere show an accumulation of lactate and lipids, which are indicative of anoxic conditions. Additionally, a basis for general temperature control and monitoring and a graphical control software have been developed and are also described. The complete platform will allow biomedical assays of therapeutic agents to be performed in the early phases of therapeutic development. Thus, small quantities of drugs or advanced nanodevices may be studied long-term under simulated living conditions that mimic the flow and distribution of nutrients.

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