Quantitative (1) H MR spectroscopic imaging of the prostate gland using LCModel and a dedicated basis-set: correlation with histologic findings.

Proton magnetic resonance spectroscopic imaging ((1) H-MRSI) has been advocated as a valuable tool for prostate cancer diagnosis. However, a barrier to widespread clinical use of this technique is the lack of robust quantification methods that yield reproducible results in an institution-independent manner. The main goal of this study was to develop a standardized and fully automated approach (LCModel-based) for quantitative prostate (1) H-MRSI. To this end, a dedicated basis set was constructed by the combination of simulated (citrate, Cit; choline, Cho, and creatine, CR) and experimentally acquired (spermine, Spm) spectra. The overlapping Spm, Cho, and Cr could be resolved and quantified individually, thus allowing for the independent assessment of glandular (Cit and Spm) and proliferative (Cho) components. Several metabolite ratios were calculated and compared to the histologic findings of prostatectomy specimens from 10 prostate cancer patients with Gleason scores (3 + 3) and (3 + 4). The Cho mole fraction and the Cho/(Cit + Spm) ratio were found to best discriminate between prostate cancer and healthy tissue. The comparison between the quantitative MRSI results and the histologic findings suggests that no correlation exists between the detected metabolic alterations and the Gleason score of low-grade tumors.

[Neuroimaging in attention deficit hyperactivity disorder]. / Neuroimagen en el trastorno por déficit de atención/hiperactividad.

INTRODUCTION: Advances in neuroimaging in the last decade have allowed a number of new findings about attention deficit hyperactivity disorder (ADHD) to be obtained. Quickly developing technology, together with the progress being made in genetics and neurochemical research, suggests a dysfunction of the fronto striatal circuit that involves the prefrontal cortex and its relationship with the basal, thalamic and cerebellar nuclei as the pathophysiological foundation of this disorder. On the other hand, neuroimaging in the future may complement clinical evaluation, which will favour more accurate diagnoses and allow the subtypes and even the mode of treatment and its monitoring to be identified. AIMS AND DEVELOPMENT: The aim of this study was to review the more significant literature on neuroimaging and ADHD and to discuss the usefulness and drawbacks of the different modes of neuroimaging techniques that can be applied with a view to gaining an improved and deeper knowledge of ADHD in the future. CONCLUSIONS: Although the development of neuroimaging in ADHD is a promising area, at the present time its diagnostic value is very restricted. One of the greatest difficulties in this respect concerns the clinical, genetic and pathophysiological heterogeneity of the disorder. Hence, given the inexistence of a specific marker, future studies will have to search for several markers that have a suitable value in the diagnosis, prognosis and/or treatment of the different subtypes of ADHD.

[Neurofibromatosis type 1 and optic pathway gliomas. A series of 80 patients]. / Neurofibromatosis tipo 1 y gliomas de vías ópticas. Una serie de 80 pacientes.

PATIENTS AND METHODS: From a series of 530 patients with neurofibromatosis type 1 (NF1), we performed a retrospective assessment of the long-term neurologic, visual, neuroimaging and evolution of 80 patients (15%) with optic pathway gliomas (OPG). All the 80 patients, 58 (72.5%) females and 22 (27.5%) males were diagnosed during childhood (below age 16 years), range 13 months to 15 years (average: 4.6 years). RESULTS: Image studies showed the distribution of the lesions among optic nerves, chiasm, tracts and radiations demonstrated that only 25% of the tumors involved only one optic nerve and 11.5% were located only in the chiasm, while 40% involved one or both optic nerves and chiasm, tracts and radiations. Two patients showed pilocytic astrocytoma in the histological study. Late diagnosis (after 7 years of age) of OPG was made in three patients and late progression was evident in three others who required surgical resection, radiotherapy or chemotherapy. CONCLUSIONS: All patients were diagnosed during childhood (below 16 years of age). Incidence was double in girls than in boys. Despite the apparent tumoral agressivity of the magnetic resonance and magnetic resonance spectroscopy images, histological findings corresponded to benign pilocytic astrocytoma. Some tumors follow the growth after 7 years. Continued monitoring of patients with NF1 into adulthood is advisable.

[Brain stem tumors associated with neurofibromatosis type 1. Presentation of 20 infantile patients]. / Tumores de tronco cerebral asociados con neurofibromatosis tipo 1. Presentación de 20 pacientes infantiles.

OBJECTIVE: To describe the clinical and imaging findings of 20 patients (12 women and 8 men) with brain stem tumors associated with neurofibromatosis type 1 (NF1). PATIENTS AND METHODS: All patients were first time studied before 11 years old. Clinical and magnetic resonance (MR) study were made in all 20 patients, and spectroscopic MR (SMR) was performed in 7 patients. Thirteen of the 20 patients (65 %) also had optic pathway tumor. Brain stem tumor identification occurred at the same time as NF1 in the patients who were studied by MR at the time of the first consult. RESULTS: Brain stem identification occurred at the same time as that of the NF1 in patients who were studied by MR from the beginning. Diffuse or localized medullary enlargement was the most frequent MR imaging and appeared in 13 patients (65%), followed by the tumor that involved all brain stem (pontine and medullary areas) that appeared in 6 patients (30 %). In the last group, one tumor showed extension through brain stem and medial cerebellar parts, another was located in the aqueduct and in the periaqueductal areas and showed slow progressive growth, and one third patient had a tumor with aggressive signs in the SMR study. Another patient had an aggressive tumor that involved the left optic nerve, chiasm, mesencephalon and upper right pontine areas. The histological study of the tumoral biopsic tissue of the two last patients showed astrocitoma degree 1 (benign tumor). The two aggressive tumors were treated with radiotheraphy and chemotherapy and they are still alive 4 and 7 years respectively after treatment. Three patients who had aqueductal obstruction and hydrocephalus were treated with shunt. The rest of patients did not receive treatment. Only one of the 20 patients died, although it was due to a malignant chiasmatic tumor, that had been treated twenty years before, and not by the brain stem tumor. CONCLUSIONS: In NF1, brain stem tumors are the most frequent tumors of the posterior fossa and the second most frequent of the central nervous system (CNS). MR and SMR are necessary to a correct identification of the tumor in some patients. Most of these tumors are benign.

[Unilateral facial and cerebral hyperplasia associated with neurofibromatosis type 1. Report of four patients]. / Hiperplasia facial y cerebral unilateral asociada a neurofibromatosis tipo 1. Presentacion de cuatro pacientes.

INTRODUCTION: Plexiform neurofibroma in any location is one of the commonest complications associated with neurofibromatosis type 1 (NF1). Plexiform neurofibroma of the upper eyelid and orbit is usually associated with ipsilateral hemifacial hyperplasia. We present four patients with NF1 and plexiform neurofibroma of the eyelid and orbit associated with hemifacial hyperplasia, who also showed hyperplasia of the unilateral cerebral hemisphere. CASE REPORTS: There are four patients, three females and one male, who consulted because of NF1 with plexiform neurofibroma of upper eyelid and hemifacial hyperplasia. Upper eyelid involvement was observed since birth and progressed during the first years of life. The patients showed normal neurological and mental development without motor or cerebellar disorders. Magnetic resonance studies demonstrated the asymmetric hyperplasia of the ipsilateral hemisphere in all four cases and of the cerebellar hemisphere in one case. The degree of hemispheric hyperplasia was related to the size and extension of the plexiform neurofibroma, as well as to the severity of the hemifacial hyperplasia. In our case which had the plexiform neurofibroma extended to the neck and the upper thorax, the hyperplasia not only affected the cerebral hemisphere but also the ipsilateral cerebellar hemisphere. All parts of the hemisphere showed increased size. The cortex of the entire hemisphere showed normal differentiation of the subcortical white matter. CONCLUSION: NF1 appears to be related with facial and cerebral ipsilateral hemihyperplasia. The relation between the size and extension of the orbital, eyelid and facial plexiform neurofibroma and the degree of asymmetry of the hemispheric hyperplasia suggest that different influences of a still unknown agent, possibly a gene, obviously related to NF1, causes both the intracranial and extracranial abnormalities.

[Glutaric aciduria type 1 with normal evolution: follow-up of one case until adult age]. / Aciduria glutárica tipo 1 con evolución normal: seguimiento de un caso hasta la edad adulta.

We present a patient of 20 years of age with glutaric aciduria type 1 (GA1) and normal psychomotor development. Her symptoms consisted of a few convulsions between 2.5 and 4.5 years of age. She was diagnosed at 9 years of age because of the typical alterations of GA1 that appeared in computed tomography and magnetic resonance (MR) imaging studies. Enzymatic activity in fibroblasts culture was nonexistent and glutarate excretion was elevated in the annual controls where this was investigated from the diagnosis of the disease so far. MR studies showed hyposignal in T1 of the subcortical white matter, severe dilatation of the Sylvian region and temporal fossa subarachnoid spaces, and hypoplasia of the subjacent cerebral parenchyma and of both temporal lobes. The corpus callosum and the surrounding zones appeared very enlarged and with signal changes. Spectroscopic MR showed signs of membrane instability and cellular impoverishment in subcortical white matter and basal ganglia and presence of lactic acid. Macrocephaly always maintained centiles over 98. The patient has no abnormal movements or motor disturbances, her behavior and intelligence being normal and she is able to follow studies of middle level.

Vacuolating megalencephalic leukoencephalopathy: 24 year follow-up of two siblings.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive disorder with a chronic progressive course. The gene, MLC1, has been localized on chromosome 22qtell and 26 different mutations have been described. We report two siblings of non-consanguineous parents who presented with characteristic features of MLC. They showed macrocephaly from the first months of life. After a short time, motor clumsiness, ataxia, seizures and psychomotor retardation were observed. During childhood, both patients had a coma that lasted several days following a minor head trauma. The eldest sister experienced a permanent deterioration of the clinical picture after the coma. Epilepsy and electroencephalographic alterations were chronic, tending to improve during adulthood. Cerebral biopsy showed normal or minor changes in the cortical grey matter, and in the white matter gliosis, increased extracellular spaces and decreased numbers of fibres with thin myelin sheets. We have followed the patients during 24 years, from the ages of 4 and 8 years to the their present ages of 28 and 32 years. Clinical and neuro-imaging follow-up showed a chronic course with more prominent progression of the white matter abnormalities than of the neurological features. A homozygous mutation of the MLC1 gene was found in both siblings. The eldest patient, 32 years-old, needs a wheel-chair but has a good contact with the family and surrounding people. The youngest, 28-years-old, shows mild ataxia, spasticity and motor clumsiness, but she is able to participate in activities of daily life.

[L-2 hydroxyglutaric aciduria in a patient with Klinefelter syndrome]. / Aciduria L-2-hidroxiglutárica en un paciente con síndrome de Klinefelter.

We present a of 22 years old patient who has a severe cerebellar disease that started during the first years of life, borderline mental level, epilepsy and Klinefelter syndrome. Brain magnetic resonance (MR) imaging revealed swollen white matter with a loss of signal on T1-weighted slices and an increase in signal intensity on T2-weighted images in both cerebral hemispheres and in both cerebellar dentate nuclei. MRI alterations did not change during the studies performed from 4 to 21 years. Blood and urine were analyzed and showed great elevation of L-2-hydroxyglutaric acid (L-2-HGA) and more discrete elevation of its metabolites and lysine. The parents of the patient are first cousins.

[Clinical progress of neonatal non-ketotic hyperglycinemia under treatment]. / Evolución de la hiperglicinemia no cetósica neonatal en tratamiento.

INTRODUCTION: Non-ketotic hyperglycinemia is a congenital error in the breakdown of glycine. The most common type is the classical neonatal form, which begins at the age of a few days with symptoms of lethargy, hypotonia, myoclonia, convulsions, apneas and, frequently, ends in death. Survivors usually develop intractable epilepsy and mental retardation. There is no effective treatment for this condition, but trials have been carried out with a therapy that diminishes the levels of glycine, benzoate (BZ), and another that blocks the excitatory effect in N-methyl-D-aspartate receptors: dextromethorphan (DTM). CASE REPORT: We report on the progress of a classical neonatal case, which began at the age of a few hours with hypotonia and stupor, without myoclonias or seizures, but with a suppression wave trace on the electroencephalogram (EEG). Cerebrospinal fluid (CSF) showed glycine levels of 141 micromol/L (the normal level is 6.66 +/- 2.66 micromol/L), with a CSF/plasma ratio of 0.19 (the normal ratio is < 0.02). Treatment was started on the thirteenth day with BZ and DTM, and alertness and eye fixation improved in just three days; at the same time the EEG readings become normal. The glycine level in plasma returned to normal at two months and that in CSF was considerably reduced, although with CSF/plasma levels that were still high. At present the patient is 4 years old, has never had convulsions, EEG results have always been normal, and continues with BZ, DTM, carnitine and diet. The patient has presented a high degree of hypermotoric behaviour, but is currently more attentive and more sociable, has been walking from the age of 35 months and has a quotient in the different areas of development of 40-50. CONCLUSIONS: The clinical progress made by our patient could be said to be anything but negligible, and we therefore recommend that treatment should be started as early as possible after diagnosis.

Proton magnetic resonance spectroscopy in dementia with Lewy bodies.

Proton magnetic resonance spectroscopy ((1)H-MRS) provides a non-invasive, in vivo insight into the brain metabolism, and has been successfully used in several neurological conditions. Our objective was to characterise the cerebral metabolic changes in dementia with Lewy bodies (DLB) patients using (1)H-MRS. Single Voxel (1)H-MRS was performed in 12 DLB patients with mild to moderate symptoms and 11 age-matched healthy controls. Volumes of interest (VOI) were selected, including white matter (WM) in the centrum semiovale and grey matter (GM) in the parasagittal parietal cortex. Main metabolic peaks corresponding to N-acetylaspartate (NAA), glutamate/glutamine (Glx), choline-containing compounds (Cho), myo-inositol (Ins), and creatine plus phosphocreatine (Cr) were identified. These areas were measured and referred to that of the water. Metabolic ratios among the different peak areas were also calculated. In comparison with the control group, DLB patients showed significantly lower mean NAA/Cr, Glx1/Cr and Cho/Cr ratios in the WM, while their Ins/Cr and Ins/NAA ratios did not differ from those of the control group. In the GM, no significant differences were found between both groups. Correlations between age at onset, disease duration, Mini-Mental State Examination, the motor section of the Unified Parkinson's Disease Rating Scale, Hoehn and Yahr staging and metabolic ratios, both for WM and GM, were not significant in DLB patients. Our spectroscopy data show WM involvement, along with GM preservation, in DLB patients with early or intermediate stages. Hence, (1)H-MRS may provide adjunctive information in the ante-mortem diagnosis of DLB.

[Advances in the physiopathology of epileptogenesis: metabolic aspects in vivo]. / Avances en la fisiopatología de la epileptogénesis: aspectos metabólicos in vivo.

This communication shows how proton magnetic resonance spectroscopy (MRS) is currently being employed in the study or the diagnosis of epilepsy. With this goal, the kind of biochemical information of cerebral parenchyma available with this non invasive technique is first introduced in a succinct way. The value of this metabolic information is then illustrated through several cases of temporal and extratemporal epilepsy, for which magnetic resonance imaging was either non diagnostic or uncertain. In this context, the asymmetry index, very useful for the lateralization of epileptogenic foci on the basis of quantitative spectroscopic criteria, is defined. Finally, other potentials of MRS, beyond its ability to elucidate the existence of neuronal damage in the epileptogenic zone, are considered. Hence, cases with postictally increased lactate, or increased glutamine/glutamate without apparent neuronal damage, are presented as good examples of the diagnostic or lateralizing value of MRS.

Avances en la fisiopatología de la epileptogénesis: aspectos metabólicos in vivo / Advances in the physiopathology of epileptogenesis: metabolic aspects in vivo

En esta ponencia se revisa el estado actual de la espectroscopía por resonancia magnética (ERM) de protón, en su aplicación al estudio y diagnóstico de la epilepsia. Para ello, primero se presenta de forma sucinta el tipo de información bioquímica del parénquima cerebral que resulta asequible con esta técnica no invasiva. La utilidad de esta información metabólica se ilustra, a continuación, sobre diversos casos de epilepsia temporal y extratemporal, para los cuales el valor diagnóstico de la imagen por RM fue nulo o incierto. En este contexto, se define el concepto de índice de asimetría, de gran utilidad para la lateralización del foco epileptógeno sobre la base de criterios espectroscópicos cuantitativos. Finalmente, se ilustran otras potencialidades de la ERM, más allá de la simple elucidación del daño neuronal en la zona epileptógena. Así, se muestran casos en los que el aumento postictal del lactato, o los niveles incrementados del par glutamato/ glutamina en ausencia de signos de daño neuronal, revisten valor diagnóstico o lateralizante (AU)

[Battered baby syndrome. Report of a case with severe sequelae]. / Síndrome del niño zarandeado. Presentación de un caso con graves secuelas.

OBJECTIVE: To present a case with shaken-baby syndrome after having seizures and respiratory problems. CLINICAL CASE: A previously normal child of 7 months of age presented an acute picture of status epilepticus with respiratory problems and periods of apnea. He was studied with electroencephalography, computerized tomography, magnetic resonance (MR) imaging and spectroscopic-MR. The child showed the presence of small subdural and epidural hematomas in both frontal regions 24 hours after the onset of the problem. The follow-up with MR studies revealed voluminous subdural bilateral hygroma that increased the size along the following six months, despite treatment with bilateral subdural-peritoneal shunt, and the patient showed infantile spasms. At 8 years of age, the patient shows severe mental retardation with autistic behavior and blindness, though he is able to walk without help and he has not seizures. The subdural hygroma decreased the size, but MR shows severe cortico-subcortical atrophy of both parieto-occipital regions. Spectroscopic MR study discloses severe neuronal lost and gliosis. CONCLUSIONS: The shaken-baby syndrome causes severe encephalopathy and vision problems, blindness in many cases, after showing voluminous subdural and/or epidural hematomas which lead to a severe neuronal lost and gliosis. Shaken-baby syndrome is not always associated with skull fracture nor is necessarily related with battered-child syndrome.

[Hypothalamic hamartomas: control of seizures after partial removal in one case]. / Hamartomas hipotalámicos: control de las crisis después de la exéresis parcial en un caso.

OBJECTIVE: To describe a patient with intractable seizures and hypothalamic hamartoma that was only partially resected with complete control of seizures and improvement in behavior after surgery. CLINICAL CASE: He had gelastic seizures from the first months of life associated with hypothalamic hamartoma. We used magnetic resonance spectroscopy to localize and measure the lesion in the temporal lobes and in the hamartoma. The relative intensity of N-acetylaspartate to creatine (NAA/Cr) and NAA/choline (Ch) were not significantly different from normal control subjects for either temporal lobes, whereas the ratio NAA/Ch was decreased and the ratio NAA/Cr was highly increased in the hamartoma. Despite only partial resection of the hamartoma, seizures have been completely controlled and the patient has recovered normal social and work activity and is ending a normal life, that follow three years after surgery. CONCLUSIONS: These findings suggest that gelastic seizures associated with hypothalamic hamartoma are generated within the hamartoma itself, and that it is possible to control epilepsy and to improve intellectual and social problems with only partial resection of the mass.

Clinical correlation of striatal 1H MRS changes in Huntington's disease.

OBJECTIVE: To study the clinical significance of metabolic alterations as measured in vivo with proton MRS in the striatum of patients with Huntington's disease (HD). METHODS: Localized, single-voxel MRS was performed on the basal ganglia of 10 HD patients (4 presymptomatic gene carriers and 6 akinetic patients) and 5 age-matched healthy individuals. Metabolite quantification was performed by referring the areas of the respective spectral peaks to that of water in the analyzed voxel. The spectroscopic findings were correlated with motor and cognitive performance in several specific tests and with the length of the CAG repeat expansion normalized for age. RESULTS: N-acetylaspartate (NAA) and creatine were reduced markedly in both groups of patients, particularly in the advanced group (approximately 60%), but the decrease was also significant in presymptomatic patients (approximately 30%) whose motor and cognitive performances were within the normal range. Both metabolites correlated highly with the motor score of the Unified Huntington's Disease Rating Scale and with computed measurements of saccadic and tapping speed. Creatine reduction was also well correlated with performance in cognitive timed tasks and with the length of CAG expansion (r = -0.81). CONCLUSION: The creatine signal appears to be an interesting marker for progression in HD and could be useful in assessing therapeutic outcome, particularly during the initial stages when most clinical indices are still within the normal range.

In vivo proton magnetic resonance spectroscopy of diseased prostate: spectroscopic features of malignant versus benign pathology.

In vivo Proton Magnetic Resonance Spectroscopy appears potentially useful for non-invasive discrimination between benign prostatic hyperplasia (BPH) and prostate carcinoma (PC). Aiming to delimit the range within which spectra from one or the other pathology should occur, and establish extreme spectroscopic features of malignant versus benign prostate disease, we performed endorectal proton MR spectroscopy on 20 patients severely affected of either benign prostatic hyperplasia (BPH) (n = 10) or prostate cancer (PC) (n = 10). They were selected on the basis of the large volume and homogeneity of their lesions, which were histologically confirmed after spectroscopy. Consequently, high-quality short-TE proton spectra with well-resolved metabolite signals, and practically free of volume averaging issues were obtained in all cases. Apart from the typical citrate, creatine, and choline signals of prostate spectra, both BPH and PC spectra showed a peak centered at 3.6 ppm which was assigned to myo-inositol. The intensity of this contribution was found significantly increased in PC cases compared to BPH. Possible relationships between neoplastic transformation and the metabolic pathways in which myo-inositol participates are discussed. Average spectroscopic profiles were calculated for both advanced pathologies, and showed obvious differentiated features. In quantitative terms, the ratio of citrate to choline peak areas as well as that of creatine to myo-inositol appeared as the most convenient to discriminate between advanced PC cases (both ratios below 1.0) and advanced BPH cases (both ratios above 1.0).

Comparison of digital rectal examination, transrectal ultrasonography, and multicoil magnetic resonance imaging for preoperative evaluation of prostate cancer.

OBJECTIVE: A prospective study was designed to compare the potentials of digital rectal examination (DRE), transrectal ultrasound (TRUS), and magnetic resonance imaging (MRI) using integrated endorectal and pelvic phased-array coils for preoperative estimation of tumor volume and local extent of prostate cancer. METHODS: Evaluation of 20 consecutive patients undergoing radical retropubic prostatectomy included DRE, TRUS with a 7.5-MHz transducer, and MRI on a 1.5-tesla GE Signa system. Step sections (5 mm) of the entire specimen were performed, and tumor volume and percentage of gland involved were calculated. RESULTS: DRE, TRUS, and endorectal and pelvic phased-array MRI showed 50, 75, and 95% of the cancers, respectively. There was a linear correlation on MRI between predicted tumor volume and pathological tumor volume (r = 0.82, p < 0.0001), but not between predicted volume on DRE or TRUS and real volume. The accuracy for detecting extracapsular penetration was 60% for DRE and TRUS and 79% for MRI. The accuracy for detecting seminal vesicle invasion was 60% for DRE, 66 for TRUS, and 89% for MRI. The negative predictive value for extracapsular and seminal vesicle extension was highest for MRI (85 and 93%, respectively). The accuracy for tumor location in the apex of the prostate was 30% for DRE, 47 for TRUS, and 89% for MRI. CONCLUSIONS: MRI with integrated endorectal and pelvic phased-array coils satisfactorily predicted tumor volume and tumor extent preoperatively. Multicoil MRI can assist in decision making as it is valuable in the definition of patients that may benefit from surgery and can be of help for evaluating the risk of a positive margin, especially in the apical resection.

[Spectroscopic magnetic resonance in hemimegalencephalus]. / Resonancia magnética espectroscópica en la hemimegalencefalia.

INTRODUCTION: Hemimegalencephalus (HM) is a disorder of cerebral migration characterized by the overdevelopment of one cerebral hemisphere. It is usually associated with pachygyria, gliosis and neurone loss. We present a study using stereoscopic magnetic resonance (SMR) in a case of HM confirmed by the pathologist. CLINICAL CASE: A girl with right HM had hemigeneralized crisis since birth. A selective right temporoccipital cortectomy was done when she was two and a half years old. The resected piece showed thickening and absence of cortical striation, neurone loss, gliosis, giant neurones and heterotopias. After a symptom-free period the crises reappeared as right fronto-parietal epileptiform anomalies. When she was four years old SMR was done to compare this area with the corresponding area of the radiologically normal left hemisphere. Comparative study showed a marked drop in N-acetyl-aspartate (NAA), glutamate (Glu) and Gaba, and increased choline (Col) and inositol (Ino). We found no difference in the creatinine levels. CONCLUSIONS: The histological findings are in concordance with the levels of metabolites found in the affected hemisphere. The drop in NAA and Glu is related to neurone loss and the increase in glial cells, and the increase in Col and Ino with increase in membranes metabolism, as is observed in the gliosis. SMR is an advance in the identification and grading of changes seen on conventional MR, when establishing the prognosis and choice of treatment in HM.

[Neuroimaging and epilepsy]. / Neuroimagen y epilepsia.

The objective of magnetic resonance neuroimaging is to define the structural changes responsible for epileptogenic lesions and to rule out the presence of dual pathology when partial epileptic seizures are being studied. To this end, the individualization and optimization of protocols and sequences is indispensable. Structural images must be complemented by clinical evidence and function studies (EEG, SPECT, PET) in order to determine whether the structural lesion is responsible for the seizure and might eventually be excised. Spectroscopy provides biochemical information that is somewhat comparable to that obtained by biopsy of the epileptogenic zone. Spectroscopic images in the near future will provide clear "blind" views of these zones. Functional magnetic resonance images will presumably be of great help in the management of these patients.

Thiol-disulfide exchange of ribonuclease inhibitor bound to ribonuclease A. Evidence of active inhibitor-bound ribonuclease.

Ribonuclease Inhibitor (RI) has been purified from pig testis. It contains 30 half-cystines whose oxidation affects its ability to bind and inhibit ribonuclease (RNase). By N-terminal sequence analyses testis RI showed to be identical to that from porcine liver, for which a characteristic all-or-none type of SH-oxidation by 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) has been reported (Fominaya, J.M., and Hofsteenge, J. (1992) J. Biol. Chem. 257, 24655-24660). Under comparable reaction conditions, testis RI bound to RNase A did not exhibit this particular type of oxidation; instead, bound RI got intermediate oxidation degrees (up to 14 thiols oxidized per RI moiety) without dissociating from RNase. Moreover, RNase bound to partially oxidized RI was able to express some (15%) of its potential activity (active complex). Only when DTNB treatments accounted for complex dissociation (> 14 thiols oxidized per RI moiety) the released RI molecules exhibited the all-or-none oxidation behavior. By both kinetic and circular dichroism analyses, conformational changes have been evidenced for the transition from the inactive to the active form of RI-RNase complex. Relaxation of RI-RNase binding without major alterations in RI structure is proposed as responsible for complex activation. The results are discussed in terms of a model for the reversible regulation of RNase activity mediated by the redox status of RI.