Ex vivo high resolution magic angle spinning metabolic profiles describe intratumoral histopathological tissue properties in adult human gliomas.

In gliomas one can observe distinct histopathological tissue properties, such as viable tumor cells, necrotic tissue or regions where the tumor infiltrates normal brain. A first screening between the different intratumoral histopathological tissue properties would greatly assist in correctly diagnosing and prognosing gliomas. The potential of ex vivo high resolution magic angle spinning spectroscopy in characterizing these properties is analyzed and the biochemical differences between necrosis, high cellularity and border tumor regions in adult human gliomas are investigated. Statistical studies applied on sets of metabolite concentrations and metabolite ratios extracted from 52 high resolution magic angle spinning recordings coming from patients with different grades of glial tumors show a strong correlation between the histopathological tissue properties and the considered metabolic profiles, regardless of the malignancy grade. The results are in agreement with the pathology obtained by the histopathological examination that succeeded the high resolution magic angle spinning measurements. The metabolite concentration set can better differentiate between the considered histopathological tissue properties compared to the ratios. Representative reference tissue models describing the metabolic behavior are extracted for characterizing the intratumoral tissue properties. The proposed metabolic profiles reflect that the metabolites behavior is interconnected, and typical biochemical patterns emerge for each histopathological tissue property.

[Quadrature coils for magnetic resonance spectroscopy in the detection of prostate cancer: single voxel acquisition does not improve the diagnostic accuracy of multivoxel images]. / Complementariedad de la espectroscopía univóxel y la imágen de espectroscopía multivóxel obtenidas mediante bobina de cuadratura para la detección del carcinoma de próstata.

OBJECTIVE: To determine the viability of quadrature coils for detecting prostate cancer using single voxel and multivoxel spectroscopy images. MATERIAL AND METHODS: We used a quadrature coil on a 1.5T MR scanner to evaluate 23 patients with suspected prostate cancer and prostate specific antigen levels greater than 4ng/ml (mean 12±8ng/ml), independently of findings at digital rectal examination. We acquired T2-weighted images and MR spectroscopy images. We also acquired single voxel studies in areas in which the T2-weighted images or the multivoxel images were altered. We used a citrate solution to verify the spectroscopic calibration. RESULTS: Using spectroscopy images and a (Co+Cr)/Cit cutoff of 1.40 in single voxel spectroscopy, we achieved a sensitivity of 92%, specificity of 55%, a negative predictive value of 86%, and a positive predictive value of 69%. Using a cutoff of 0.75 decreased specificity slightly (45%). The (Co+Cr)/Cit ratio calculated for the single volume obtained from the most abnormal area in the T2-weighted images and in the multivoxel spectroscopy slices was not significantly different between cancerous and non-cancerous tissues (ANOVA, p=0.1), although there was a clear trend toward increased coefficients with hyperplasia and neoplastic degeneration. CONCLUSION: The quadrature coil enables multivoxel and single voxel spectroscopic images of clinically and technically acceptable quality to be obtained. Using single voxel spectroscopy does not improve the diagnostic performance of multivoxel spectroscopy and T2-weighted images.

[Total brain T2-hyperintense lesion-volume and the axonal damage in the normal-appearing white matter of brainstem in early lapsing-remitting multiple sclerosis]. / Relación entre el volumen lesional cerebral total en resonancia magnética secuencia T2 y el daño neuroaxonal en la sustancia blanca aparentemente normal del tronco del encéfalo en la esclerosis múltiple remitente-recurrente.

AIM: To evaluate the relationship between the total brain T2-hyperintense lesion volume (TBT2LV) and the axonal damage in the normal-appearing white matter of brainstem measured by 1H-MRS in a group of early relapsing-remitting multiple sclerosis patients. SUBJECTS AND METHODS: 40 relapsing-remitting multiple sclerosis patients and ten sex- and age-matched healthy subjects were prospectively studied for two years. T2-weighted MR and 1H-MRS imaging were acquired at time of recruitment and at year two. The TBT2LV was calculated with a semiautomatic program; N-acetylaspartate (NAA), creatine (Cr) and choline (Cho) resonances areas were integrated with jMRUI program and the ratios were calculated for four volume elements that represented the brainstem. RESULTS: At basal study we obtained an axonal loss (as a decrement of NAA/ Cho ratio) in the group of patients compared with controls (p = 0.017); this axonal loss increased at the second year of the follow-up for patients (NAA/Cho decrease, p = 0.004, and NAA/Cr decrease, p = 0.002) meanwhile control subjects had no significant metabolic changes. Higher lesion load was correlated with a poor clinical outcome, being the correlation between the basal TBT2LV and the Expanded Disability Status Scale at second year (r = 0.299; p = 0.05). Besides, axonal loss was not homogeneous for all multiple sclerosis patients, being stronger in the subgroup of patients with high basal TBT2LV (p = 0.043; ANOVA). CONCLUSION: Our data suggest that axonal damage is early in multiple sclerosis and higher in patients high basal TBT2LV, suggesting a possible relationship between these two phenomena.

MRS as endogenous molecular imaging for brain and prostate tumors: FP6 project "eTUMOR".

Molecular imaging has become during the last years in an important tool for supporting cancer diagnosis and prognosis. PET and SPECT are the most common molecular imaging techniques, although very promising and specific biological molecular agent contrast for CT and MRI are being recently developed. However, the above imaging techniques require exogenous contrast agents and usually a sole molecular image can be obtained at once. On the contrary, in vivo magnetic resonance spectroscopy (MRS), in particular 1H MRS can simultaneously provide several molecular images using endogenous metabolites. In addition to biochemical spatial information from molecular imaging spectroscopy, MRS can also provide average metabolite profile of the selected affected tissue region. Initially MRS, especially 1H MRS, was extensively applied to complete and improve the diagnosis and prognosis of central nervous system (CNS) pathologies, in particular brain tumors. However, during the last years the MRS applications have been extent to the diagnosis of different very common cancer types such as breast, prostate, colon carcinoma, and ovarian, among others. Likewise, MRS has been also used for lymph node assessment. In this contribution, the added value of MRS for the diagnosis, prognosis, and treatment selection of two different, important types of cancer: (1) brain tumors and (2) prostate, will be presented and discussed. Brain tumors are the leading cause of death in children under 15, and although in adults, brain cancers are proportionately less common than other cancers, it is a devastating disease with high mortality. There is a great need to increase our understanding of brain tumor biology to improve diagnosis and to develop new treatments. 1H MRS is currently the only noninvasive method that can be used to investigate molecular profile of brain tumors and also provide molecular images, more than six in one acquisition, of the distribution of chemicals in a tumor, which are also generally heterogeneous. A summary of the applications of 1H MRS to the in vivo diagnosis and prognosis of brain tumors will be presented. In addition, examples of metabolite limits, infiltration and high cellularity location for neurosurgery applications by MRS molecular images will be shown. Likewise, new ex vivo methods of studying the detailed biochemistry of tumor biopsies as metabolomic (high resolution magic angle spinning [HR-MAS]) and transcriptomic (DNA microarrays) will be discussed as complementary to in vivo MRS (FP6 European project eTUMOR). A preliminary comparison between molecular images from PET and 1H MRS will be also presented. Finally, the application of 1H MRS to the improvement of prostate diagnosis and prognosis, the second leading cause of cancer death, will also discussed, with particular attention to the location cancer contribution from MRS molecular images.

High-resolution solution NMR structure of the Z domain of staphylococcal protein A.

Staphylococcal protein A (SpA) is a cell-wall-bound pathogenicity factor from the bacterium Staphylococcus aureus. Because of their small size and immunoglobulin (IgG)-binding activities, domains of protein A are targets for protein engineering efforts and for the development of computational approaches for de novo protein folding. The NMR solution structure of an engineered IgG-binding domain of SpA, the Z domain (an analog of the B domain of SpA), has been determined by simulated annealing with restrained molecular dynamics on the basis of 671 conformational constraints. The Z domain contains three well-defined alpha-helices corresponding to polypeptide segments Lys7 to Leu17 (helix 1), Glu24 to Asp36 (helix 2), and Ser41 to Ala54 (helix 3). A family of ten conformers representing the solution structure of the Z domain was computed by simulated annealing of restrained molecular dynamics using the program CONGEN. The average of the root-mean-square deviations (r.m. s.d.) of the individual NMR conformers, relative to the mean coordinates, for the backbone atoms N, Calpha and C' of residues Phe5 through Ala56 is 0.69 A; the corresponding backbone r.m.s.d. for the three-helical core is 0.44 A. Helices 1, 2 and 3 are antiparallel in orientation (Omega12=-170(+/-4) degrees , Omega13=+16(+/-3) degrees , Omega23=+173(+/-7) degrees ). A comparison of backbone amide hydrogen/deuterium exchange rates in free and IgG-bound Z domains demonstrates that the amide protons of helices 1, 2 and 3 are protected from rapid exchange in both states, indicating that all three helices are also intact in the IgG-bound state. These solution NMR results differ from the previously determined X-ray structure of the similar SpA B domain in complex with the Fc fragment of a human IgG antibody, where helix 3 is not observed in the electron density map and from the solution NMR structure of the B domain, where helix 3 is observed but helix 1 is tilted by approximately 30 degrees with respect to helices 2 and 3. Hydrogen-bonded N-cap and C-cap formation is observed for all three helices of the Z domain; these capping interactions appear to be highly conserved in the five homologous domains of SpA.

Evidence of Wallerian degeneration in normal appearing white matter in the early stages of relapsing-remitting multiple sclerosis: a HMRS study.

OBJECTIVE: Wallerian degeneration in normal appearing white matter in early relapsing-remitting multiple sclerosis (RRMS), and its correlation with the number of relapses and disease duration. Background Recent pathological studies have demonstrated Wallerian degeneration in normal appearing white matter (NAWM) in multiple sclerosis (MS), in established RRMS, and in chronic MS. However, the presence of Wallerian degeneration early in the disease and its correlation with relapse and with disease duration has not been studied. METHODS: We performed proton magnetic resonance spectroscopic imaging in 21 MS patients, and 4 healthy controls, age and gender matched, aged under 45 years, with a maximum of 4 years since first bout, and an EDSS score of less than 3.0. N-acetyl-aspartate (NAA) (an index of axonal integrity) was measured in the NAWM from the pons and the cerebellar peduncles. RESULTS: We observed that the NAA levels were abnormally low in the NAWM in the early RRMS patients (p = 0.04, Student's t-test). The decrease in the NAA concentration correlated with disease duration in the two areas studied (p = 0.03 for pons and p = 0.04 for cerebellar peduncle); and with the number of previous relapses (Pearson's correlation = -0.582, p < 0.002). CONCLUSION: Wallerian degeneration measured by the NAA concentration at pons and cerebellar peduncles is present early in the disease and correlates with the number of relapses and disease duration.

A study of the conformational equilibrium of DL-oligophenylalanines in nonpolar solvents in the presence and absence of lipids by high-performance liquid chromatography.

The usefulness of high-performance size-exclusion liquid chromatography (HPSEC) for the separation of dimeric and monomeric species of DL-alternating oligophenylalanines is demonstrated for the first time. The experimental data obtained as a function of time fit a simple dimer-monomer equilibrium in a nonpolar solvent such as tetrahydrofuran. A higher extent of monomerization and a decrease in the time required for reaching equilibrium were detected in the presence of either water or phosphatidylcholine. The analysis of the relative proportions of the two separated species under equilibrium conditions has allowed the influence of the oligopeptide chain length on the stability of dimeric species to be determined. The advantages of this methodology, in combination with spectroscopic techniques, in studies on autoassociating peptides are considered.

Contribution to the study of the alteration of lipase activity of Candida rugosa by ions and buffers.

A semipurified C. rugosa lipase (LS) has been prepared from commercial lipase (LC) using an economical procedure. The presence of sugars and glycopeptides has been detected in LS and LC. Pure lipase only has covalently bonded sugars. The hydrolysis of olive oil catalyzed by LS and commercial lipase (LC) is sensitive to the presence of cations Na(I), Mg(II), Ca(II), and Ba(II) and to the nature of buffer. Highest enzyme activity is obtained with 0.1M Tris/HCl buffers and the combination of NaCl 0.11M and CaCl2 0.11M. Fluorescence spectroscopy analysis of LC, LS, and both pure isoenzymes lipases A and B, was used to analyze the interaction of the lipase with these effectors. Inorganic cations Na or Ca do not interact with pure enzyme LA but do interact with LC and LS and do so slightly with LB. The organic cations (morfolinium or tris) interact with pure lipases. We postulate that the increase in the lipase activity produced by Na(I) or Ca(II) is related with interfacial phenomena, but the increase might be more specific in the hydrolysis of olive oil in the presence of Tris-HCl or morfoline-HCl buffer, owing to enzyme-buffer interaction.

[Differences in the spectroscopy of the lesions of the remitting relapsing form of multiple sclerosis shown by magnetic resonance]. / Diferencias en la espectroscopía de las lesiones de esclerosis múltiple en su forma remitente recurrente mediante resonancia magnética.

INTRODUCTION: Multiple sclerosis (MS) is a chronic demyelinating disorder of the central nervous system, characterized by the presence of inflammatory lesions. OBJECTIVE: To analyze the biochemical profile of the demyelinating lesions of the initial forms of MS (remitting relapsing) by analyzing the proton magnetic resonance spectra (1H MRS) to characterize the process of demyelination and relate it to the metabolites and clinical variables analyzed. PATIENTS AND METHODS: We analyzed the largest demyelinating lesions in eight patients with remitting relapsing MS (RRMS) using the technique of single volume 1H MRS (VOI) with short echo time. The spectra of the white matter of two healthy control were used as reference. RESULTS: NAA/Cr and NAA/Cho value ratios decrease and mI/Cr one increase in all spectra lesions as compared to healthy controls. In four of the eight patients, the Cho/Cr was higher than in the controls. Qualitative and quantitative differences in the resonances of macromolecules were observed, related to the biochemistry of the process of demyelination. These differences in NAA/Cr, Cho/Cr, mI/Cr and macromolecules probably represent different stages in the evolution of the plaques. CONCLUSIONS: MRS is a non invasive technique able to observe biochemical variations related to the evolution process of demyelination. Activity of the lesion is shown by the increment of resonances around 0.9 1.3 ppm. An increase in mI seems to occur at an early stage of demyelination and later the NAA is reduced. The initial forms of MS show metabolic alterations in the plaques which are similar to the most advanced forms of MS.

Study of the inferior colliculus in patients with schizophrenia by magnetic resonance spectroscopy.

INTRODUCTION. Previous studies have suggested morphometric and functional abnormalities in the inferior colliculus in patients with schizophrenia. Auditory hallucinations are one of the central symptoms in schizophrenia. In this complex and multidimensional event both attention and emotion are thought to play a key role. AIM. To study metabolic changes in the inferior colliculus, a nucleus integrated in the auditory pathway, in patients with schizophrenia and the possible relationship with auditory hallucinations. SUBJECTS AND METHODS. Magnetic resonance spectroscopic imaging studies were performed in 30 right-handed patients with chronic schizophrenia (19 of them with auditory hallucinations) and 28 controls. A magnetic resonance spectroscopic imaging 2D slice was acquired and the voxels representative of both inferior colliculi were selected. N-acetylaspartate (NAA), creatine (Cr) and choline (Cho) peak areas were measured. RESULTS. The patients with schizophrenia showed a NAA/Cr significant reduction in the right inferior colliculus compared to the control subjects. The metabolic data in the right inferior colliculus were correlated with emotional auditory hallucinations items. CONCLUSIONS. The contribution of the inferior colliculus on neural underpinnings of auditory hallucinations is particularly relevant for the right inferior colliculus and is centered on attention-emotional component of this symptom.

TITLE: Estudio del coliculo inferior de pacientes con esquizofrenia mediante espectroscopia de resonancia magnetica.Introduccion. Algunos estudios anteriores en pacientes con esquizofrenia han sugerido alteraciones morfometricas y funcionales en el coliculo inferior. Las alucinaciones auditivas son uno de los sintomas centrales en la esquizofrenia. Se piensa que en este evento complejo y multidisciplinar, tanto la atencion como la emocion desempeñan un papel clave. Objetivo. Estudiar los cambios metabolicos en el coliculo inferior, un nucleo integrado en la via auditiva, en pacientes con esquizofrenia y su posible relacion con las alucinaciones auditivas. Sujetos y metodos. Se llevaron a cabo estudios de espectroscopia de resonancia magnetica en 30 pacientes diestros con esquizofrenia cronica (19 de ellos con alucinaciones auditivas) y 28 controles. Se adquirio una secuencia 2D de espectroscopia de resonancia magnetica y se seleccionaron los voxeles representativos de ambos coliculos inferiores. Se calculo el area de los picos de N-acetilaspartato (NAA), creatina (Cr) y colina (Co). Resultados. Los pacientes con esquizofrenia mostraron una reduccion significativa de NAA/Cr en el coliculo inferior derecho comparados con los sujetos control. Los datos metabolicos en el coliculo inferior derecho se correlacionaron con los items emocionales de las alucinaciones auditivas. Conclusiones. La contribucion del coliculo inferior a las bases neuronales de las alucinaciones auditivas es particularmente relevante para el coliculo inferior derecho y se centra en el componente atencional-emocional de este sintoma.

Non-negative blind source separation techniques for tumor tissue typing using HR-MAS signals.

Given High Resolution Magic Angle Spinning (HR-MAS) signals from several glioblastoma tumor subjects, the goal is to differentiate between tumor tissue types by separating the different sources that contribute to the profile of each spectrum. Blind source separation techniques are applied for obtaining characteristic profiles for necrosis, high cellular tumor and border tumor tissue, and providing the contribution (abundance) of each tumor tissue to the profile of the spectra. The problem is formulated as a non-negative source separation problem. We illustrate the effectiveness of the proposed methods and we analyze to which extent the dimension of the input space could influence the performance by comparing the results on the full magnitude signals and on dimensionally reduced spaces.

Comparative metabolic profiling of paediatric ependymoma, medulloblastoma and pilocytic astrocytoma.

Brain tumours are the most common solid tumours in children and a major cause of childhood mortality. The most common paediatric brain tumours include ependymomas, cerebellar astrocytomas and medulloblastomas. These brain tumours are highly heterogeneous regarding their histology, prognosis and therapeutic response. Subtle biochemical changes can be detected in intact tissues by High-Resolution Proton Magnetic Angle Spinning Spectroscopy (HR-MAS) revealing the status of tumour microheterogeneity and metabolic alterations before they are morphologically detectable. In this study, we present metabolic profiles by HR-MAS of 20 intact tissue samples from paediatric brain tumours. Tumour types include ependymoma, medulloblastoma and pilocytic astrocytoma. The metabolic characterization of paediatric brain tumour tissue by HR-MAS spectroscopy provided differential patterns for these tumours. The metabolic composition of the tumour tissue was highly consistent with previous in vivo and ex vivo studies. Some resonances detected in this work and not previously observed by in vivo spectroscopy also show potential in determining tumour type and grade (fatty acids, phenylalanine, glutamate). Overall, this work suggests that the additional information obtained by NMR metabolic profiling applied to tissue from paediatric brain tumours may be useful for assessing tumour grade and determining optimum treatment strategies.

Proton magnetic resonance spectroscopy imaging in the study of human brain cancer.

Magnetic resonance spectroscopic imaging (MRSI) is a non-invasive imaging technique that provides metabolic information on brain tumor. This biochemical information can be processed and presented as density maps of several metabolites, among them N-acetylaspartate (marker of neuronal viability), choline (marker of membrane turnover), creatine (related to the energy state of the cells), myo-Inositol (exclusively found in astrocytes), lipids and lactate (observed in necrosis and other pathological processes) which mean relevant information in the context of brain tumors. Thus, this technique is a multiparametrical molecular imaging method that can complete the magnetic resonance imaging (MRI) study enabling the detection of biochemical patterns of different features and aspects of brain tumors. In this article, the role of MRSI as a molecular imaging technique to provide biochemical information on human brain tumors is reviewed. The most frequent questions and situations in the study of human brain tumors in clinical settings will be considered, as well as the distinction of neoplastic lesions from non neoplastic, the tumor type identification, the study of heterogeneity and infiltration of normal appearing white matter and the therapy following with detection of side effects. The great amount of data in MRSI acquisition compared to the single voxel techniques requires the use of automated methods of quantification, but the possibility to obtain self-reference in the non-affected areas allows different strategies for data handling and interpretation, as presented in the literature. The combination of MRSI with other physiological MRI techniques and positron emission tomography is also included in this review.

Spectroscopic metabolomic abnormalities in the thalamus related to auditory hallucinations in patients with schizophrenia.

OBJECTIVE: Previous studies have found neurochemical abnormalities in thalamic nuclei in patients with schizophrenia. These abnormalities have been associated with information processing deficiencies and symptom formation. There are no metabolic spectroscopy studies in patients with schizophrenia attending to auditory hallucinations. The aim of the present study is to explore metabolic Magnetic Resonance Spectroscopy (MRS) ratio differences in the thalamus between schizophrenic patients with and without auditory hallucinations and control subjects. METHODS: MRS studies (MRI 1.5 T unit) were performed in 49 patients with schizophrenia (30 with auditory hallucinations and 19 without auditory hallucinations) and 37 controls. (1)H MRS imaging was used to acquire 2 transverse slices (TR/TE 2700/272 ms, region of interest 110 x 100 x 23 mm). In the quantitative analysis four elements of volume (9.2 x 9.2 x 23 x 4 mm), added into one spectrum representative of each thalamus, were chosen in the slice passing through the main body of the thalamus. The areas of metabolites were integrated with the jMRUI program. RESULTS: The patients with schizophrenia had significantly lower bilateral NAA/Cho ratios when compared with healthy subjects. There was also a lower NAA/Cho ratio in the right thalamus in patients with auditory hallucinations compared to patients without auditory hallucinations and control subjects. Significant correlations were found between metabolic ratios and BPRS, PANSS and PSYRATS scores, age of onset of auditory hallucinations, and age of subjects. CONCLUSIONS: Choline and NAA ratio abnormalities determined by thalamic spectroscopy may be related to the pathogenesis of auditory hallucinations in patients with schizophrenia.

[Dementias: diagnostic contribution of imaging and proton magnetic resonance spectroscopy]. / Demencias: contribución diagnóstica de la imagen y de la espectroscopia de resonancia magnética de protón.

INTRODUCTION: The objective is analyze the complementarity between 1H magnetic resonance spectroscopy (MRS) and magnetic resonance (MR) imaging in the global diagnosis of Alzheimer's disease (AD) or vascular dementia (VD). METHODS: We studied 168 patients with cognitive impairment from AD, VD, mild cognitive impairment (MCI) and major depression. All patients were evaluated by brain MR imaging and MRS using two sample volumes localized at right medial temporal gyrus and posterior parietal gyrus. Metabolites analyzed were N-acetylaspartate (NAA), myo-Inositol (mI), Choline (Cho) and creatine (Cr), as standard references for obtaining the Co/Cr, mI/Cr and NAA/Cr ratios. Imaging and spectroscopy alterations were graded from 0 to 4 and the average of both was used to draw ROC and SROC curves. Area under ROC curve (Az) was used as a measure of discriminative ability. RESULTS: Combination of MR imaging and MRS significantly improved AD diagnosis (Global Az: 0.722 vs. MR imaging Az: 0.624; p: 0.003). However, the combination of MR imaging and MRS did not improve VD diagnosis. SROC curve obtained for the diagnosis of global dementia was Az: 0.6658 with 0.67 sensitivity and 0.65 specificity. CONCLUSIONS: Combination of both MR techniques significantly improved AD diagnosis versus MR imaging alone. More studies are needed to enhance VD classification. Metabolic data found by MRS can be useful to differentiate cognitive impairment

Axonal loss is progressive and partly dissociated from lesion load in early multiple sclerosis.

OBJECTIVE: To assess the relationship between the spectroscopically measured axonal damage in the normal-appearing white matter of the brainstem, the total brain T2-hyperintense lesion volume (T2LV), and disability in patients with early relapsing-remitting multiple sclerosis (RRMS). METHODS: Forty-three RRMS patients and 10 sex- and age-matched healthy controls were prospectively studied for 2 years. T2-weighted magnetic resonance (MR) images and proton MR spectroscopy were acquired at the time of recruitment and at year 2. Brainstem was considered, where large tracts join together, as a suitable region to detect early axonal damage. The T2LV was calculated with a semiautomatic program; N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) resonances areas were integrated with the jMRUI program, and the ratios were calculated for the sum of the volume elements represented at brainstem. RESULTS: The basal NAA/Cho ratio was significantly decreased in patients compared with controls. After 2-year follow-up, there was a decrease in the NAA/Cho (-9%; p = 0.002) and NAA/Cr (-13%; p = 0.001) ratios, and an increase in the T2LV (19%; p = 0.043) in multiple sclerosis patients, whereas control subjects had no significant metabolic changes. Significant NAA/Cr ratio decreases were observed in both patients, with and without relapses, whereas T2LV only increased in patients with relapses. The final Expanded Disability Status Scale (EDSS) score correlated with T2LV at baseline, but no significant correlations were found between metabolic values, T2LV change, or EDSS score over the study period. CONCLUSIONS: Our data reveal an early and progressive axonal damage in relapsing-remitting multiple sclerosis. Axonal loss and T2 lesion volume seem to be at least partly dissociated processes in early stages of the disease.

[Cognitive impairment: classification by proton magnetic resonance spectroscopy and the contributions of conventional magnetic resonance imaging]. / Deterioro cognitivo: clasificación mediante espectroscopia de resonancia magnética de protón y contribución de la imagen convencional.

OBJECTIVE: To analyze the diagnostic accuracy of proton magnetic resonance spectroscopy (1H MRS) in patients with cognitive impairment and to establish the usefulness of complementary information provided by conventional magnetic resonance imaging (MRI). MATERIAL AND METHODS: 64 patients with cognitive impairment, including Alzheimer's disease (AD) (n=31), vascular dementia (n=6), mild cognitive impairment (MCI) (n=9), and major depression (n=18), were studied. All patients underwent cerebral MRI and single-volume 1H MRS using two echo times (TE, 31 and 136 ms) in the posterior cingulate gyrus and right temporal lobe. The metabolites analyzed were N-acetylaspartate (NAA), myo-Inositol (mI), choline (Ch), and creatine (Cr), and the ratios of Ch/Cr, mI/Cr, NAA/mI and NAA/Cr were calculated. In order to differentiate among the different types of cognitive impairment, the alterations in imaging and spectroscopy findings were graded from 0 to 4, as was the mean combination of the two, and then ROC curves were obtained. RESULTS: Statistically significant differences were found between the spectra of patients with dementia (AD and vascular dementia) and those without dementia (MCI and depression) in the posterior cingulate gyrus. The NAA/mI ratio yielded the best area under the ROC curve, with the best sensitivity (82.5%) and specificity (72.7%) in the diagnosis of AD. The NAA/mI and mI/Cr quotients differentiated between the four degenerative pathologies causing the cognitive impairment. The combination of MRI and 1H MRS significantly improved the accuracy of the diagnosis of AD. CONCLUSIONS: The metabolic differences found among patients with cognitive impairment using 1H MRS can be useful for differentiating AD, vascular dementia, MCI, and depression. The combination of spectroscopy and MRI findings is useful in the diagnosis of AD.

Conformational and structural analysis of the equilibrium between single- and double-strand beta-helix of a D,L-alternating oligonorleucine.

Alternating sequences of D and L residues in peptides are directly related to the formation of several kinds of regular helical conformations usually called beta-helices. The major feature of these structures is that they can be associated with the transmembrane ion-conducting channel activity in some natural antibacterial peptides. The study of alternating D,L synthetic peptides is critical to understand how factors such as surrounding media, main chain length, type of side chain and terminal groups, among others, can determine the adoption of a specific kind of beta-helix. Early studies pointed out that the peptides Boc-(D-NLeu-L-NLeu)(6)-D-MeNLe-L-Nl-D-Nl-L-Nl-OMe (Boc: tert-butyloxycarbonyl) and Boc-L-Nle-(D-Nle-L-Nle)(5)-D-MeNle-L-Nle-D-Nle-L-Nle-OMe adopt in chloroform a unique detectable conformation single beta(4.4)- and double beta(5.6) upward arrow downward arrow -helix, respectively. The influence of terminal groups on the final stable conformation of N-formylated peptides has been studied in this work. The initial basic NMR data analysis of a synthetic alternating D,L-oligopeptide with ten norleucines, N-methylated on the residue 7 and having HCO- and -OMe as terminal groups clearly indicates the coexistence of two different conformations in equilibrium. NMR data and molecular dynamics calculations point to a dimeric antiparallel beta-helix structure beta(5.6) upward arrow downward arrow for the main conformation. On the other hand, NMR data suggest a single beta-helix structure beta(4.4) for the second conformation. Finally, a thermodynamic analysis of the equilibrium between both conformations has been carried out by one-dimensional NMR measurements at ten different temperatures. The temperature at which 50% of dimer conformation is dissociated is 319 K. In addition, the dimer-monomer equilibrium curve obtained shows a DeltaG>0 for the whole range of studied temperatures, and its behavior can be considered similar to the thermodynamic denaturation protein processes.

Solution structure of a D,L-alternating oligonorleucine as a model of double-stranded antiparallel beta-helix.

Conformational characteristics of alternating D,L linear peptides are of particular interest because of their capacity to form transmembrane channels with different transport properties, as some natural antibiotics do. Single- and double-stranded beta-helical structures are common for alternating D,L peptides. The stability of the beta-helix depends on several structural factors, such as the backbone peptide length, type and position of side chains, and nature of terminal groups. The NMR and molecular dynamics solution conformation of a synthetic alternating D,L-oligopeptide with 15 norleucines (XVMe) has been used as a model to get insight in to the conformational features of double-stranded beta-helix structures. The NH chemical shift values (delta(NH)) and long-range nuclear Overhauser effects (NOE) cross peaks, in particular interstrand connectivities, clearly point to an antiparallel double-stranded beta-helix for the XVMe major conformation in solution. An extensive set of distances (from NOE cross peaks) and H-bonds (from delta(NH)) has been included in the molecular dynamics calculations. The experimental NMR data and theoretical calculations clearly indicate that the most probable conformation of XVMe in solution is a double-strand antiparallel beta(5.6) increasing decreasing-helix structure.