Analysis of a Novel Peptide That Is Capable of Inhibiting the Enzymatic Activity of the Protein Kinase A Catalytic Subunit-Like Protein from Trypanosoma equiperdum.

A 26-residue peptide possessing the αN-helix motif of the protein kinase A (PKA) regulatory subunit-like proteins from the Trypanozoom subgenera (VAP26, sequence = VAPYFEKSEDETALILKLLTYNVLFS), was shown to inhibit the enzymatic activity of the Trypanosoma equiperdum PKA catalytic subunit-like protein, in a similar manner that the mammalian heat-stable soluble PKA inhibitor known as PKI. However, VAP26 does not contain the PKI inhibitory sequence. Bioinformatics analyzes of the αN-helix motif from various Trypanozoon PKA regulatory subunit-like proteins suggested that the sequence could form favorable peptide-protein interactions of hydrophobic nature with the PKA catalytic subunit-like protein, which possibly may represent an alternative PKA inhibitory mechanism. The sequence of the αN-helix motif of the Trypanozoon proteins was shown to be highly homologous but significantly divergent from the corresponding αN-helix motifs of their Leishmania and mammalian counterparts. This sequence divergence contrasted with the proposed secondary structure of the αN-helix motif, which appeared conserved in every analyzed regulatory subunit-like protein. In silico mutation experiments at positions I234, L238 and F244 of the αN-helix motif from the Trypanozoon proteins destabilized both the specific motif and the protein. On the contrary, mutations at positions T239 and Y240 stabilized the motif and the protein. These results suggested that the αN-helix motif from the Trypanozoon proteins probably possessed a different evolutionary path than their Leishmania and mammalian counterparts. Moreover, finding stabilizing mutations indicated that new inhibitory peptides may be designed based on the αN-helix motif from the Trypanozoon PKA regulatory subunit-like proteins.

Disorder and partial folding in the regulatory subunit hinge region of Trypanosoma brucei protein kinase A: The C-linker portion inhibits the parasite's protein kinase A.

Microbial pathogens, such as Trypanosoma brucei, have an enormous impact on global health and economic systems. Protein kinase A of T. brucei is an attractive drug target as it is an essential enzyme which differs significantly from its human homolog. The hinge region of this protein's regulatory domain is vital for enzymatic function, but its conformation is unknown. Here, the secondary structure of this region has been characterized using NMR and CD spectroscopies. More specifically, three overlapping peptides corresponding to residues T187-I211, G198-Y223 and V220-S245 called peptide 1, peptide 2 and peptide 3, respectively, were studied. The peptide 1 and peptide 2 are chiefly unfolded; only low populations (<10%) of α-helix were detected under the conditions studied. In contrast, the peptide 3 contains a long α-helix whose population is significantly higher; namely, 36% under the conditions studied. Utilizing the dihedral φ and ψ angles calculated on the basis of the NMR data, the conformation of the peptide 3 was calculated and revealed an α-helix spanning residues E230-N241. This α-helix showed amphiphilicity and reversible unfolding and refolding upon heating and cooling. Most fascinating, however, is its capacity to inhibit the activity of the catalytic domain of Trypanosoma equiperdum protein kinase A even though it is quite distinct from the canonical inhibitor motif. Based on this property, we advance that peptoids based on the peptide 3 α-helix could be novel leads for developing anti-trypanosomal therapeutics.

Biochemical characterization of the cAMP-dependent protein kinase regulatory subunit-like protein from Trypanosoma equiperdum, detection of its inhibitory activity, and identification of potential interacting proteins.

An enriched fraction of an inhibitor of both the catalytic subunit of the cAMP-dependent protein kinase (PKA) from pig heart and a Trypanosoma equiperdum PKA catalytic subunit-like protein (TeqC-like) was obtained from the soluble fraction of T. equiperdum parasites after three consecutive purification steps: sedimentation through a linear 5-20% sucrose gradient, diethylaminoethyl-Sepharose anion-exchange chromatography, and Bio-Sil Sec-400-S size-exclusion high-performance liquid chromatography. The inhibitor was identified as the T. equiperdum PKA regulatory subunit-like protein (TeqR-like) on the basis of Western blot and mass spectrometry analyses, and behaved as an uncompetitive or anti-competitive inhibitor of the parasite TeqC-like protein, with respect to a fluorescently labeled substrate (kemptide, sequence: LRRASLG), showing a Ki of 1.17 µM. The isolated protein possesses a molecular mass of 57.54 kDa, a Stokes radius of 3.64 nm, and a slightly asymmetric shape with a frictional ratio f/fo = 1.43. As revealed during the purification steps and by immunoprecipitation experiments, the TeqR-like and TeqC-like proteins were not associated forming a heterooligomeric complex, differing from traditional PKA subunits. Co-immunoprecipitation results followed by mass spectrometry sequencing identified two isoforms of the parasite heat-shock protein 70, α-tubulin, and ß-tubulin as candidates that interact with the TeqR-like protein in T. equiperdum.

Sequence Analysis of the cAMP-Dependent Protein Kinase Regulatory Subunit-Like Protein From Trypanosoma brucei.

PURPOSE: Study the N-terminal, C-terminal, and linker regions of the TbPKAr using homology modeling. METHODS: The amino acid sequences of the N-terminal, C-terminal, and linker regions of the TbPKAr were individually examined by means of BLAST analysis and in silico secondary structure predictions with several programs. RESULTS: The TbPKAr C-terminal region, showed a well-folded α/ß structure, which consists of two concurrent flattened ß-barrel-shaped domains that are separated by an elongated central α-helix similar to its mammalian counterpart, the TbPKAr linker region contains a PKA phosphorylation site and was predicted to be rather disordered. Our analysis also indicated that the TbPKAr N-terminal region lacks a docking/dimerization domain but is enriched in motifs known as leucine-rich repeats (LRR). CONCLUSION: The replacement of the docking/dimerization domain by different structural motifs suggests the inability of TbPKAr to form homodimers; however, the function of the TbPKAr N-terminal LRR-containing domain in Kinetoplastidae parasites is still unknown.

Glucose deprivation activates a cAMP-independent protein kinase from Trypanosoma equiperdum.

Kemptide (sequence: LRRASLG) is a synthetic peptide holding the consensus recognition site for the catalytic subunit of the cAMP-dependent protein kinase (PKA). cAMP-independent protein kinases that phosphorylate kemptide were stimulated in Trypanosoma equiperdum following glucose deprivation. An enriched kemptide kinase-containing fraction was isolated from glucose-starved parasites using sedimentation throughout a sucrose gradient, followed by sequential chromatography on diethylaminoethyl-Sepharose and Sephacryl S-300. The trypanosome protein possesses a molecular mass of 39.07-51.73 kDa, a Stokes radius of 27.4 Ǻ, a sedimentation coefficient of 4.06 S and a globular shape with a frictional ratio f/fo = 1.22-1.25. Optimal enzymatic activity was achieved at 37 °C and pH 8.0, and kinetic studies showed Km values for ATP and kemptide of 11.8 ± 4.1 and 24.7 ± 3.8 µm, respectively. The parasite enzyme uses ATP and Mg2+ and was inhibited by other nucleotides and/or analogues of ATP, such as cAMP, AMP, ADP, GMP, GDP, GTP, CTP, ß,γ-imidoadenosine 5'-triphosphate and 5'-[p-(fluorosulfonyl)benzoyl] adenosine, and by other divalent cations, such as Zn2+, Mn2+, Co2+, Cu2+, Ca2+ and Fe2+. Additionally, the trypanosome kinase was inhibited by the PKA-specific heat-stable peptide inhibitor PKI-α. This study is the first biochemical and enzymatic characterization of a protein kinase from T. equiperdum.

Fluram-Kemptide-Lys8 Non-radioactive Assay for Protein Kinase A.

The cAMP-dependent protein kinase (PKA) is the best understood member of the superfamily of serine-threonine protein kinases and is involved in controlling a variety of cellular processes. Measurements of PKA activity traditionally relied on the use of [(32)P]-labeled ATP as the phosphate donor and a protein or peptide substrate as the phosphoaceptor. Recently non-isotopic assays for the PKA have been developed and this paper presents an improvement of a fluorometric assay for measuring the activity of PKA. Three peptides were synthesized with the following sequences: LRRASLG (Kemptide), LRRASLGK (Kemptide-Lys8) and LRRASLGGGLRRASLG (Bis-Kemptide), these have in common the substrate sequence recognized by the PKA (RRXS/TΨ), where X is any amino acid and Ψ is a hydrophobic amino acid. Optimal conditions were established for the non-radioactive assay to detect the PKA activity by phosphorylation of these three peptides that are covalently linked to fluorescamine at their N-terminus. The phosphorylated and non-phosphorylated peptides were easily separated by electrophoresis, identified and quantified with optical densitometry and ultraviolet light. The fluorescamine-labeled Kemptide-Lys8 substrate (Fluram-Kemptide-Lys8) was used to calculate the Km and Vmax of the catalytic subunit of PKA from pig heart and showed a detection limit of 260 pmol, a linear range between 700 and 1150 pmol with a linear regression R (2) = 0.956.

Immunological identification of a cAMP-dependent protein kinase regulatory subunit-like protein from the Trypanosoma equiperdum TeAp-N/D1 isolate.

Polyclonal immunoglobulin Y (IgY) antibodies were produced in chicken eggs against the purified R(II)-subunit of the cAMP-dependent protein kinase (PKA) from pig heart, which corresponds to the Sus scrofa R(II)α isoform. In order to evaluate whether Trypanosoma equiperdum possessed PKA R-like proteins, parasites from the Venezuelan TeAp-N/D1 strain were examined using the generated anti-R(II) IgY antibodies. Western blot experiments revealed a 57-kDa polypeptide band that was distinctively recognized by these antibodies. Likewise, polyclonal antibodies raised in mice ascites against the recombinant T. equiperdum PKA R-like protein recognized the PKA R(II)-subunit purified from porcine heart and the recombinant human PKA R(I)ß-subunit by immunoblotting. However, a partially purified fraction of the parasite PKA R-like protein was not capable of binding cAMP, implying that this protein is not a direct downstream cAMP effector in T. equiperdum. Although the function of the S. scrofa PKA R(II)α and the T. equiperdum PKA R-like protein appear to be different, their cross-reactivity together with results obtained by bioinformatics techniques corroborated the high level of homology exhibited by both proteins. Moreover, its presence in other trypanosomatids suggests an important cellular role of PKA R-like proteins in parasite physiology.

Binding of rhodopsin and rhodopsin analogues to transducin, rhodopsin kinase and arrestin-1.

AIM: To investigate the interaction of reconstituted rhodopsin, 9-cis-retinal-rhodopsin and 13-cis-retinal-rhodopsin with transducin, rhodopsin kinase and arrestin-1. METHODS: Rod outer segments (ROS) were isolated from bovine retinas. Following bleaching of ROS membranes with hydroxylamine, rhodopsin and rhodopsin analogues were generated with the different retinal isomers and the concentration of the reconstituted pigments was calculated from their UV/visible absorption spectra. Transducin and arrestin-1 were purified to homogeneity by column chromatography, and an enriched-fraction of rhodopsin kinase was obtained by extracting freshly prepared ROS in the dark. The guanine nucleotide binding activity of transducin was determined by Millipore filtration using ß,γ-imido-((3)H)-guanosine 5'-triphosphate. Recognition of the reconstituted pigments by rhodopsin kinase was determined by autoradiography following incubation of ROS membranes containing the various regenerated pigments with partially purified rhodopsin kinase in the presence of (γ-(32)P) ATP. Binding of arrestin-1 to the various pigments in ROS membranes was determined by a sedimentation assay analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. RESULTS: Reconstituted rhodopsin and rhodopsin analogues containing 9-cis-retinal and 13-cis-retinal rendered an absorption spectrum showing a maximum peak at 498 nm, 486 nm and about 467 nm, respectively, in the dark; which was shifted to 380 nm, 404 nm and about 425 nm, respectively, after illumination. The percentage of reconstitution of rhodopsin and the rhodopsin analogues containing 9-cis-retinal and 13-cis-retinal was estimated to be 88%, 81% and 24%, respectively. Although only residual activation of transducin was observed in the dark when reconstituted rhodopsin and 9-cis-retinal-rhodopsin was used, the rhodopsin analogue containing the 13-cis isomer of retinal was capable of activating transducin independently of light. Moreover, only a basal amount of the reconstituted rhodopsin and 9-cis-retinal-rhodopsin was phosphorylated by rhodopsin kinase in the dark, whereas the pigment containing the 13-cis-retinal was highly phosphorylated by rhodopsin kinase even in the dark. In addition, arrestin-1 was incubated with rhodopsin, 9-cis-retinal-rhodopsin or 13-cis-retinal-rhodopsin. Experiments were performed using both phosphorylated and non-phosphorylated regenerated pigments. Basal amounts of arrestin-1 interacted with rhodopsin, 9-cis-retinal-rhodopsin and 13-cis-retinal-rhodopsin under dark and light conditions. Residual arrestin-1 was also recognized by the phosphorylated rhodopsin and phosphorylated 9-cis-retinal-rhodopsin in the dark. However, arrestin-1 was recognized by phosphorylated 13-cis-retinal-rhodopsin in the dark. As expected, all reformed pigments were capable of activating transducin and being phosphorylated by rhodopsin kinase in a light-dependent manner. Additionally, all reconstituted photolyzed and phosphorylated pigments were capable of interacting with arrestin-1. CONCLUSION: In the dark, the rhodopsin analogue containing the 13-cis isomer of retinal appears to fold in a pseudo-active conformation that mimics the active photointermediate of rhodopsin.

Associação dos biomarcadores com aterosclerose e risco para doença coronariana em portadores de HIV / Association of biomarkers with atherosclerosis and risk for coronary artery disease in patients with HIV

FUNDAMENTO: O uso maciço da Terapia Antirretroviral (TARV) na população com vírus da imunodeficiência adquirida (HIV) coincidiu com um aumento das doenças cardiovasculares, causa importante de morbimortalidade nesse grupo. OBJETIVO: Determinar a frequência de aterosclerose carotídea e avaliar a associação entre os níveis dos biomarcadores e o espessamento da camada médio-intimal carotídea em indivíduos HIV positivos, atendidos em serviços de referência para HIV em Pernambuco. MÉTODOS: Corte transversal com 122 pacientes HIV positivos. Considerou-se aterosclerose carotídea subclínica o aumento da espessura da camada média intimal da carótida comum > 0,8 milímetros ou placas no ultrassom de carótidas. Os biomarcadores inflamatórios analisados foram IL6, IL1-β, TNF-α, PCR-ultrassensível, sVCAM-1 e sICAM-1. RESULTADOS: Dos 122 pacientes analisados, a maioria era de homens (60,7%), com > 40 anos (57,4%), em uso de TARV (81,1%). A prevalência de aterosclerose foi de 42,6% (52 casos). Pacientes com idade acima de 40 anos e Framingham intermediário ou alto apresentaram maior chance de desenvolver aterosclerose na análise univariada. Idade acima de 40 anos (OR = 6,57 IC 2,66 -16,2; p = 0,000), sexo masculino (OR = 2,76 IC 1,12-6,79; p = 0,027) e a condição de síndrome metabólica (OR = 2,27 IC 0,94-5,50; p = 0,070) mostraram-se associados à aterosclerose na análise multivariada. Níveis elevados de citocinas inflamatórias e moléculas de adesão não mostraram associação com a presença de aterosclerose. CONCLUSÃO: Não houve associação entre os biomarcadores inflamatórios, moléculas de adesão e presença de aterosclerose carotídea. Entretanto, evidenciou-se em homens, pessoas com mais de 40 anos, portadores de escore de Framingham intermediário/alto ou síndrome metabólica maior chance de aterosclerose subclínica.

BACKGROUND: The massive use of Highly-Active Antiretroviral Therapy (HAART) in individuals with human immunodeficiency virus (HIV) coincided with an increase in cardiovascular disease, a major cause of morbidity and mortality in this group. OBJECTIVE: To determine the frequency of carotid atherosclerosis and the association between biomarker levels and carotid intimal-medial thickening in HIV-positive individuals treated for HIV at referral centers in Pernambuco. METHODS: This was a cross-sectional study of 122 HIV-positive patients. Subclinical carotid atherosclerosis was considered with the presence of increased intimal-medial thickness of the common carotid artery > 0.8 mm or plaques in the carotid ultrasound. The following inflammatory biomarkers were analyzed: IL6, IL1-β, TNF-α, high-sensitivity CRP, sVCAM-1 and sICAM-1. RESULTS: Of the 122 patients analyzed, most were men (60.7%) aged > 40 years (57.4%) receiving HAART (81.1%). The prevalence of atherosclerosis was 42.6% (52 cases). Patients older than 40 years and intermediate or high Framingham score were more likely to develop atherosclerosis at the univariate analysis. Age older than 40 years (OR = 6.57, 95%CI: 2.66 to 16.2, p = 0.000), male gender (OR = 2.76, 95%CI: 1.12 to 6.79, p = 0.027) and presence of syndrome metabolic (OR = 2.27, 95%CI: 0.94 to 5.50, p = 0.070) were associated with atherosclerosis at the multivariate analysis. Elevated levels of inflammatory cytokines and adhesion molecules were not associated with the presence of atherosclerosis. CONCLUSION: There was no association between inflammatory biomarkers, adhesion molecules and presence of carotid atherosclerosis. However, a higher chance of subclinical atherosclerosis was observed in men, those older than 40 years, with intermediate / high Framingham score or metabolic syndrome.

Association of biomarkers with atherosclerosis and risk for coronary artery disease in patients with HIV.

BACKGROUND: The massive use of Highly-Active Antiretroviral Therapy (HAART) in individuals with human immunodeficiency virus (HIV) coincided with an increase in cardiovascular disease, a major cause of morbidity and mortality in this group. OBJECTIVE: To determine the frequency of carotid atherosclerosis and the association between biomarker levels and carotid intimal-medial thickening in HIV-positive individuals treated for HIV at referral centers in Pernambuco. METHODS: This was a cross-sectional study of 122 HIV-positive patients. Subclinical carotid atherosclerosis was considered with the presence of increased intimal-medial thickness of the common carotid artery > 0.8 mm or plaques in the carotid ultrasound. The following inflammatory biomarkers were analyzed: IL6, IL1-ß, TNF-α, high-sensitivity CRP, sVCAM-1 and sICAM-1. RESULTS: Of the 122 patients analyzed, most were men (60.7%) aged > 40 years (57.4%) receiving HAART (81.1%). The prevalence of atherosclerosis was 42.6% (52 cases). Patients older than 40 years and intermediate or high Framingham score were more likely to develop atherosclerosis at the univariate analysis. Age older than 40 years (OR = 6.57, 95%CI: 2.66 to 16.2, p = 0.000), male gender (OR = 2.76, 95%CI: 1.12 to 6.79, p = 0.027) and presence of syndrome metabolic (OR = 2.27, 95%CI: 0.94 to 5.50, p = 0.070) were associated with atherosclerosis at the multivariate analysis. Elevated levels of inflammatory cytokines and adhesion molecules were not associated with the presence of atherosclerosis. CONCLUSION: There was no association between inflammatory biomarkers, adhesion molecules and presence of carotid atherosclerosis. However, a higher chance of subclinical atherosclerosis was observed in men, those older than 40 years, with intermediate / high Framingham score or metabolic syndrome.

Extracción de metabolitos ácidos durante el análisis de catecolaminas en tejido cerebral de ratas / Extraction of acid metabolites during the analysis of catecholamines in rat brain tissue / Extração de metabólitos ácidos durante a análise de catecolaminas no tecido cérebro de rato

A través del método de equilibrio batch se comparó la adsorción de las catecolaminas Dopamina (DA), Noradrenalina (NA) y Adrenalina (A), y de los metabolitos ácido dihidroxifenilacético (Dopac) y ácido indolacético (5- HIAA) en las fases sólidas octadecil (C18) hidrofóbica, diol (C Diol) hidrofílica y de intercambio catiónico débil (WCX). En la fase sólida WCX a pH 4,0 se observó un 78% de adsorción de catecolaminas y 68% de adsorción de Dopac. Las isotermas de adsorción de las catecolaminas en la fase WCX son de tipo Langmuir. La adrenalina tiene mayor afinidad que la dopamina por la fase WCX a pH 4,0 y la dopamina mayor afinidad que el Dopac y éste es coadsorbido sobre las catecolaminas adsorbidas en la fase WCX. Un ensayo con solventes orgánicos demostró que el tolueno extrajo selectivamente de una mezcla sintética el Dopac y el 5-HIAA coadsorbido, mientras que en una muestra de tejido cerebral de ratas experimentales fueron extraídos el Dopac y el ácido homovanílico (HVA). Estos resultados sirvieron para proponer un paso adicional de extracción con solventes orgánicos para la separación de metabolitos ácidos durante la extracción en fase sólida (EFS) en el análisis de catecolaminas.

The adsorptions of Dopamine (DA), Noradrenaline (NA), and Adrenaline (A) catecholamines were compared by using the batch equilibrium method, as well as those of the dihydroxyphenylacetic acid (Dopac) and indolacetic acid (5-HIAA) metabolites on the hydrophobic octadecyl (C18), hydrophilic diol (C Diol) and weak cation exchange (WCX) solid phases. On the WCX solid phase at pH 4.0, catecholamines adsorption of 78% and Dopac adsorption of 68% were observed. The adsorption isotherms of catecholamines on the for the WCX phase at pH 4.0 than dopamine, dopamine has greater affinity than Dopac, and this latter is coadsorbed over the adsorbed catecholamines on the WCX phase. A trial with organic solvents demonstrated that toluene selectively extracted Dopac and the coadsorbed 5-HIAA from a synthetic mix, while in a brain tissue specimen from experimental rats, Dopac and homovanilic acid (HVA) were extracted. These results served to propose an additional extraction step with organic solvents throughout the separation of acid metabolites during solid phase extraction (EFS) for the analysis of catecholamines.

Specific interactions of sticholysin I with model membranes: an NMR study.

Sticholysin I (StnI) is an actinoporin produced by the sea anemone Stichodactyla helianthus that binds biological and model membranes forming oligomeric pores. Both a surface cluster of aromatic rings and the N-terminal region are involved in pore formation. To characterize the membrane binding by StnI, we have studied by (1)H-NMR the environment of these regions in water and in the presence of membrane-mimicking micelles. Unlike other peptides from homologous actinoporins, the synthetic peptide corresponding to residues 1-30 tends to form helix in water and is more helical in either trifluoroethanol or dodecylphosphocholine (DPC) micelles. In these environments, it forms a helix-turn-helix motif with the last alpha-helical segment matching the native helix-alpha(1) (residues 14-24) present in the complete protein. The first helix (residues 4-9) is less populated and is not present in the water-soluble protein structure. The characterization of wild-type StnI structure in micelles shows that the helix-alpha(1) is maintained in its native structure and that this micellar environment does not provoke its detachment from the protein core. Finally, the study of the aromatic resonances has shown that the motional flexibility of specific rings is perturbed in the presence of micelles. On these bases, the implication of the aromatic rings of Trp-111, Tyr-112, Trp-115, Tyr-132, Tyr-136, and Tyr-137, in the interaction between StnI and the micelle is discussed. Based on all the findings, a revised model for StnI interaction with membranes is proposed, which accounts for differences in its behavior as compared with other highly homologous sticholysins.

Judicialização da saúde em âmbito hospitalar: implantação de sistemas de redução dos efeitos negativos ao SUS

O presente projeto propõe a organização e estruturação permanente de Assessoria Jurídica no Hospital de Pronto Socorro de Canoas Deputado Nelson Marchezan - HPSC, com o objetivo principal de atuação, através de diferentes mecanismos, para a aproximação do Judiciário à realidade e aos problemas do Sistema Único de Saúde (SUS), buscando formas eficientes de minimização dos problemas advindos da judicialização da saúde, especificamente na área hospitalar. Com a medida pretende-se uma maior compreensão da estrutura e operacionalização do sistema de saúde pelos órgãos do Poder Judiciário e da sociedade em geral, com o objetivo de redução dos encaminhamentos judiciais liminares inadequados, e, quando inevitáveis, que sejam feitos de forma ordenada e integrada à rede de saúde, auxiliando o Estado na organização do sistema para a valorização dos preceitos e diretrizes do SUS

[Multivoxel spectroscopy with short echo time: choline/N-acetyl-aspartate ratio and the grading of cerebral astrocytomas]. / Espectroscopia multivoxel com tempo de eco curto: a razão colina/N-acetil-aspartato e a graduação dos astrocitomas cerebrais.

The choline/N-acetyl-aspartate (Cho/NAA) ratio, obtained by the multivoxel spectroscopy with short echo time (TE), was evaluated, in the histological grading of the brain astrocytomas (grades I, II and III-IV) in comparison with the normal cerebral parenchyma. A significant increase (p<0.05) in the average ratios of Cho/NAA was observed in the three astrocytoma groups studied in relation to normal tissue, having a tendency to increase with the increase in grading, without any statistic significance, which corresponded to: 0.53+/-0.24 in the control group, 1.19+/-0.49 in grade I, 1.58+/-0.65 in grade II and 5.13+/-8.12 in the high grade group (grades III-IV), with variation in the values encountered. There was an increase in the Cho/NAA ratio in 4/5 (80%) in grade I, 5/6 (83%) in grade II and 10/20 (50%) in grades III and IV. We conclude that multivoxel spectroscopy with short TE can be used in discriminating between normal parenchyma and neoplasm tissue. However, not all neoplasm tissue studied presented an increase in Cho/NAA, especially in the group with higher grade of malignancy.

Espectroscopia multivoxel com tempo de eco curto: a razão colina/N-acetil-aspartato e a graduação dos astrocitomas cerebrais / Multivoxel spectroscopy with short echo time: choline/N-acetyl-aspartate ratio and the grading of cerebral astrocytomas

Avaliou-se a relação colina/N-acetil-aspartato (Co/NAA), obtida pela espectroscopia multivoxel com tempo de eco (TE) curto, na graduação histológica dos astrocitomas encefálicos (graus I, II e III-IV), comparando com o parênquima cerebral normal. Observou-se aumento significativo (p<0,05) das relações médias de Co/NAA nos três grupos de astrocitomas estudados em relação ao tecido normal, havendo tendência de elevação com o aumento da graduação, sem significância estatística, que correspondeu a: 0,53±0,24 no grupo controle, 1,19±0,49 no grau I, 1,58±0,65 no grau II e 5,13±8,12 no grupo de alto grau (graus III-IV). Houve aumento da relação Co/NAA em 4/5 (80 por cento) dos pacientes com grau I, 5/6 (83 por cento) com grau II e 10/20 (50 por cento) com graus III e IV. Concluiu-se que a espectroscopia multivoxel com TE curto pode ser usada na discriminação entre o parênquima normal e o tecido neoplásico. Entretanto, nem todo tecido neoplásico estudado apresentou aumento da relação Co/NAA, principalmente o grupo com maior malignidade.

The choline/N-acetyl-aspartate (Cho/NAA) ratio, obtained by the multivoxel spectroscopy with short echo time (TE), was evaluated, in the histological grading of the brain astrocytomas (grades I, II and III-IV) in comparison with the normal cerebral parenchyma. A significant increase (p<0.05) in the average ratios of Cho/NAA was observed in the three astrocytoma groups studied in relation to normal tissue, having a tendency to increase with the increase in grading, without any statistic significance, which corresponded to: 0.53±0.24 in the control group, 1.19±0.49 in grade I, 1.58±0.65 in grade II and 5.13±8.12 in the high grade group (grades III-IV), with variation in the values encountered. There was an increase in the Cho/NAA ratio in 4/5 (80 percent) in grade I, 5/6 (83 percent) in grade II and 10/20 (50 percent) in grades III and IV. We conclude that multivoxel spectroscopy with short TE can be used in discriminating between normal parenchyma and neoplasm tissue. However, not all neoplasm tissue studied presented an increase in Cho/NAA, especially in the group with higher grade of malignancy.