MRI of peripheral nerve lesions of the lower limbs.

Our aim is to illustrate the contribution of MRI to diagnosis of lesions of the lower-limb nerve trunks. We report six patients who had clinical and electrophysiological examination for a peroneal or tibial nerve palsy. MRI of the knee showed in three cases a nonenhancing cystic lesion of the peroneal nerve suggesting an intraneural ganglion cyst, confirmed by histological study in one case. One patient with known neurofibromatosis had an enhancing nodular lesion of the peroneal nerve compatible with a neurofibroma. Two patients had diffuse hypertrophy with high signal on T2-weighted images, without contrast enhancement of the sciatic nerve or its branches. These lesions were compatible with localised hypertrophic neuropathy. In one case, biopsy of the superficial branch of the peroneal nerve showed insignificant axonal degeneration. MRI can provide information about the size and site of the abnormal segment of a nerve before treatment and can be used to distinguish different patterns of focal lesion.

Structure of antibody-bound peptides and retro-inverso analogues. A transferred nuclear Overhauser effect spectroscopy and molecular dynamics approach.

The three-dimensional structures of the two L-peptides, H-CGGIRGERA-OH, called L(A), and H-CGGIRGERG-OH, called L(G), corresponding or close to the IRGERA sequence present in the C-terminal region (residues 130-135) of histone H3, and their retro-inverso analogues HO-mAreGriGGC-NH2, called RI(mA), and HO-mGreGriGGC-NH2, called RI(mG), have been studied by two-dimensional 1H NMR and molecular dynamics calculations in association with a monoclonal antibody generated against L(A). At 25 degrees C, the affinity constants of the monoclonal antibody with respect to RI(mA) and RI(mG) were 75- and 270-fold higher than those measured with the homologous L(A) and L(G) peptides, respectively. Due to the spontaneous epimerization of the mA malonic residue, RI(mA) gave rise to two sets of resonances. With regard to the NH amide region, one set was similar to that for RI(mG) while the second was similar to those for the parent L-peptides L(A) and L(G). The antibody-bound conformations of the two couples of L- and retro-inverso peptides have been analyzed using molecular modeling calculations based on the transferred NOE interproton distances. Folded structures appeared in both cases with a type II' beta-turn in the parent GGIR sequence and a type I' beta-turn in the retro-inverso reGr sequence.

The third-dimensional structure of the complex between an Fv antibody fragment and an analogue of the main immunogenic region of the acetylcholine receptor: a combined two-dimensional NMR, homology, and molecular modeling approach.

Binding of autoantibodies to the acetylcholine receptor (AChR) plays a major role in the autoimmune disease Myasthenia gravis (MG). In this paper, we propose a structure model of a putative immunocomplex that gives rise to the reduction of functional AChR molecules during the course of MG. The model complex consists of the [G(70), Nle(76)] decapeptide analogue of the main immunogenic region (MIR), representing the major antigenic epitope of AChR, and the single chain Fv fragment of monoclonal antibody 198, a potent MG autoantibody. The structure of the complexed decapeptide antigen [G(70), Nle(76)]MIR was determined using two-dimensional nmr, whereas the antibody structure was derived by means of homology modeling. The final complex was constructed using calculational docking and molecular dynamics. We termed this approach "directed modeling," since the known peptide structure directs the prestructured antibody binding site to its final conformation. The independently derived structures of the peptide antigen and antibody binding site already showed a high degree of surface complementarity after the initial docking calculation, during which the peptide was conformationally restrained. The docking routine was a soft algorithm, applying a combination of Monte Carlo simulation and energy minimization. The observed shape complementarity in the docking process suggested that the structure assessments already led to anti-idiotypic conformations of peptide antigen and antibody fragment. Refinement of the complex by dynamic simulation yielded improved surface adaptation by small rearrangements within antibody and antigen. The complex presented herein was analyzed in terms of antibody-antigen interactions, properties of contacting surfaces, and segmental mobility. The structural requirements for AChR complexation by autoantibodies were explored and compared with experimental data from alanine scans of the MIR peptides. The analysis revealed that the N-terminal loop of the peptide structure, which is indispensable for antibody recognition, aligns three hydrophobic groups in a favorable arrangement leading to the burial of 40% of the peptide surface in the binding cleft upon complexation. These data should be valuable in the rational design of an Fv mutant with much improved affinity for the MIR and AChR to be used in therapeutic approaches in MG.

Solution structure of a retro-inverso peptide analogue mimicking the foot-and-mouth disease virus major antigenic site. Structural basis for its antigenic cross-reactivity with the parent peptide.

The antigenic activity of a 19-mer peptide corresponding to the major antigenic region of foot-and-mouth disease virus and its retro-enantiomeric analogue was found to be completely abolished when they were tested in a biosensor system in trifluoroethanol. This suggests that the folding pattern, which is alpha-helix in trifluoroethanol (confirmed by CD measurement), does not correspond to the biologically relevant conformation(s) recognized by antibodies. The NMR structures of both peptides were thus determined in aqueous solution. These studies showed that the two peptides exhibit similar folding features, particularly in their C termini. This may explain in part the cross-reactive properties of the two peptides in aqueous solution. However, the retro-inverso analogue appears to be more rigid than the parent peptide and contains five atypical beta-turns. This feature may explain why retro-inverso foot-and-mouth disease virus peptides are often better recognized than the parent peptide by anti-virion antibodies.

Solution structures of the fibronectin-like Leishmania gp63 SRYD-containing sequence in the free and antibody-bound states--transferred NOE and molecular dynamics studies.

The anti-SRYD monoclonal antibody (mAbSRYD) raised against the IASRYDQL synthetic octapeptide, the 250-257 sequence of the Leishmania major surface glycoprotein gp63 recognizes both SRYD-containing peptides and the whole cognate major surface protein on intact parasites. Two SRYD-containing peptides, which antigenically and functionally mimic the RGDS sequence of fibronectin and efficiently inhibit parasite attachment to the macrophage receptors, were studied by two-dimensional transferred nuclear Overhauser effect experiments in the presence of mAbSRYD. The antibody-bound IASRYDQL octapeptide solution conformation was determined on the basis of 55 interproton-distance restraints, derived from NMR measurements. Eighteen structures which were first generated using an approach combining distance geometry and molecular dynamics, converge by energy minimization toward a folded structure with an average rmsd from the experimental data of less than 0.05 nm for the overall backbone and 0.025 nm for the SRYD motif. A distorted gamma-turn was found, stabilized by the backbone-backbone D255-NH to R253-CO hydrogen bond, while the R253 and D255 side chains are pointing in opposite directions. This latter antibody-bound structure is compared with that of the free octapeptide in dimethylsulfoxide solution, and with the crystal structure of the RYD fragment in OPG2 Fab, an antireceptor antibody that mimics the RGD cell adhesion site. On this basis, a mechanism for IASRYDQL-receptor interaction is discussed.

Solution structure and lipid binding of a nonspecific lipid transfer protein extracted from maize seeds.

The three-dimensional solution structure of a nonspecific lipid transfer protein extracted from maize seeds determined by 1H NMR spectroscopy is described. This cationic protein consists of 93 amino acid residues. Its structure was determined from 1,091 NOE-derived distance restraints, including 929 interresidue connectivities and 197 dihedral restraints (phi, psi, chi 1) derived from NOEs and 3J coupling constants. The global fold involving four helical fragments connected by three loops and a C-terminal tail without regular secondary structures is stabilized by four disulfide bridges. The most striking feature of this structure is the existence of an internal hydrophobic cavity running through the whole molecule. The global fold of this protein, very similar to that of a previously described lipid transfer protein extracted from wheat seeds (Gincel E et al., 1994, Eur J Biochem 226:413-422) constitutes a new architecture for alpha-class proteins. 1H NMR and fluorescence studies show that this protein forms well-defined complexes in aqueous solution with lysophosphatidylcholine. Dissociation constants, Kd, of 1.9 +/- 0.6 x 10(-6) M and > 10(-3) M were obtained with lyso-C16 and -C12, respectively. A structure model for a lipid-protein complex is proposed in which the aliphatic chain of the phospholipid is inserted in the internal cavity and the polar head interacts with the charged side chains located at one end of this cavity. Our model for the lipid-protein complex is qualitatively very similar to the recently published crystal structure (Shin DH et al., 1995, Structure 3:189-199).

Two-dimensional 1H-NMR studies of maize lipid-transfer protein. Sequence-specific assignment and secondary structure.

Correlation spectroscopy (COSY), total correlation spectroscopy (TOCSY) and NOE spectroscopy (NOESY) experiments have been used to assign sequentially the 1H 500-MHz NMR spectra of a non-specific (ns) lipid-transfer protein extracted from maize seeds. The spin-system identification and sequential assignment were combined with secondary-structure determination to identify most of the proton resonances of this 93-residue protein. From the sequential connectivities it was established that the secondary structure mainly involved four helical fragments: H1, H2, H3 and H4. This secondary structure was compared with that of wheat ns-lipid-transfer protein recently determined. The four helices are located in nearly the same regions, but helix H4 is appreciably longer in the maize protein than in the wheat protein. Comparison of the transfer activities reveals that the maize protein is more efficient than the wheat ns-lipid-transfer protein and that this difference is probably due to the affinity of the lipid for the binding site and not to the interfacial activation, i.e. adsorption of the ns-lipid-transfer protein to the membrane. From these results, it is suggested that helix H4 is a part of the lipid-binding site or contributes to the folding of this site. The present data define the basis for a further modelling of the three-dimensional structure of the maize ns-lipid-transfer protein which will be compared with that of the wheat ns-lipid-transfer protein in order to establish structure/activity relationships for this class of carriers by using natural ns-lipid-transfer protein mutants.

A multiple primer pairs polymerase chain reaction for the detection of human genital papillomavirus types.

We describe a polymerase chain reaction (PCR) based on the simultaneous detection of multiple strains of papillomavirus in a single reaction tube. This PCR method was specific and sensitive. We have validated this multiplex procedure on a collection of typed cervical biopsies specimens, and applied it to the detection of viruses in some clinical samples.

Granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha in patients with human immunodeficiency virus (HIV) type 1 infection.

Variations in cytokine production in patients with human immunodeficiency virus (HIV) infection could be involved in the physiopathology and in the progression of the disease. Therefore we studied the level of granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF alpha) produced in patients with HIV infection at stage II (asymptomatic seropositives) and stage IV (AIDS) of the CDC classification, by using an enzyme amplified sensitivity immunoassay. We measured the level of GM-CSF and TNF alpha in supernatant of phytohemagglutinin-activated peripheral blood mononuclear cells from patients and healthy individuals. In one out of 10 stage II patients and 4 out of 14 stage IV patients, we obtained higher levels of GM-CSF than the mean + 2 S.D. of controls, but in 3 stage IV patients with very low CD4+ T lymphocyte counts (< 50/mm-3) compared to other patients, the GM-CSF values were very low. High levels of TNF alpha were detected in 3 out of 10 stage II and 6 out of 11 stage IV patients. The high values of TNF alpha were associated with high values of GM-CSF in stage II and in most of AIDS patients except those with very low CD4+ T cell counts, who produced low levels of GM-CSF. Plasma levels of cytokines were evaluated in 10 stage II, 22 stage IV patients and 20 controls. Increased levels of GM-CSF (more than 9 pg/ml) were observed in the plasma from 8 out of 10 stage II patients and 17 out of 22 stage IV patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Progress in multidimensional NMR investigations of peptide and protein 3-D structures in solution. From structure to functional aspects.

2-D and 3-D NMR techniques were used to investigate the conformations in solution of several peptides and proteins for which crystalline structures are not available yet. Insect defensin A is a small (40 aa) antibiotic protein exhibiting a characteristic 'loop-helix-beta-sheet' structure. A striking analogy was found with charybdotoxin, a scorpion toxin in which a CSH (cysteine stabilized alpha-helix) motif is also present. Wheat phospholipid transfer protein (PLTP) (90 aa) has a 3-D structure resulting from the packing of four helices and of a C-terminal less well-defined fragment. Preliminary results show that PLTP forms a complex with lyso-PC and that such an interaction results in a conformational change affecting principally the C-terminal half of the protein. A last example is given with surfactin, a lipopeptide biosurfactant from bacterial origin. Its protonated form shows a very compact structure in which the two acidic residues located on the top of a 'horse saddle' topology face each other, whereas the ionized form could adopt a more extended conformation. A common property of these compounds is their capacity to interact with lipids. The present structural data open the way for a further establishment of structure-activity relationships.

Detection of Chlamydia trachomatis by use of polymerase chain reaction.

A polymerase chain reaction (PCR) assay was developed for detection of Chlamydia trachomatis DNA. One primer set was used, from the published sequence of the common C. trachomatis plasmid. Detection of amplified sequences was carried out by agarose gel electrophoresis. Analysis of 106 clinical samples tested by cell culture and PCR showed a sensitivity of 100% when PCR was compared with cell culture.

[Presymptomatic diagnosis in Huntington chorea families using the gene amplification technique]. / Diagnostic présymptomatique dans les familles de chorée de Huntington par utilisation de la technique d'amplification génique.

The presymptomatic diagnosis of Huntington chorea (HC) by genic amplification (PCR: polymerase chain reaction) of a DNA G8 sequence containing a polymorphic HindIII site was tested in a particular HC genealogy. The advantage of this method are discussed.

Regional cerebral blood flow during comprehension and speech (in cerebrally healthy subjects).

Regional cerebral blood flow (rCBF) was measured by the xenon-133 inhalation method in 10 cerebrally healthy subjects at rest and during linguistic activation tests. These consisted of a comprehension test (binaural listening to a narrative text) and a speech test (making sentences from a list of words presented orally at 30-s intervals). The comprehension task induced a moderate increase in the mean right CBF and in both inferior parietal areas, whereas the speech test resulted in a diffuse increase in the mean CBF of both hemispheres, predominating regionally in both inferior parietal, left operculary, and right upper motor and premotor areas. It is proposed that the activation pattern induced by linguistic stimulation depends on not only specific factors, such as syntactic and semantic aspects of language, but also the contents of the material proposed and the attention required by the test situation.

[Mass spectrometry of peptides]. / Spectrométrie de masse des peptides.

Recent progress in biochemistry has shown the occurrence of many important peptides, among antibiotics, immunostimulants, hormones and neuromediators. The mass spectrometric study of these components by classical ionization techniques such as electron impact, chemical ionization or field desorption require a prior chemical derivatization because of their amphoteric properties, their low volatility and low thermostability. Recent improvements in methods of ionization, fast atom bombardment, secondary ion mass spectrometry, or mass spectrometry/mass spectrometry have made it possible to study the structure of peptides with more than 15 amino acid residues and eased mass spectra interpretation. Through the different methodologies described in this review three characteristic informations can be obtained concerning the molecular mass of peptides, the nature of constituent amino acids and the peptidic sequence and even quantitative measurements can be performed.

[A case of aphasia with speech disorders by infarction of the left caudate nucleus and putamen]. / Un cas d'aphasie avec troubles du discours par infarctus des noyaux caudé et lenticulaire gauches. .

An infarction involving the left putamen, caudate nucleus and the anterior limb of the internal capsule, resulted in aphasia with semantic paraphasias, verbal incoherence and verbal memory impairment. Cerebral blood flow (CBF) studies with 133Xe inhalation at 20 days post onset showed, on one hand, a bilateral lowering of cortical blood flow and on the other hand a left frontal-parietal hypoperfusion area. Spontaneous recovery occurred within 2 months. While the mean CBF became normal at 14 months post onset, a relative hypoperfusion area persisted on the anterior left hemispheric cortex. On the basis of these findings and current CBF and metabolic studies carried out in patients with subcortical lesions, the authors discuss the role of cortical and subcortical structures in subcortical aphasic syndromes. The importance of reciprocal connections between cortex, striatum and thalamus is stressed.

[Osseous choristoma of the choroid]. / Choristome osseux de la choroïde.

Two patients developed bone choristoma of the choroid, one case being unilateral and the other bilateral. In both cases the clinical diagnosis was confirmed by B scan ultrasonography and computerized axial tomography. Infrared angiography with indocyanin green was carried out on both eyes of the patient with bilateral lesions. The angiogram showed multiple small vessels within the tumor. However, the angiogram with indocyanin green was quite different from the angiogram observed in cavernous choroidal hemangioma. One patient had an associated cleft palate, this being supportive evidence of the hypothesis of a developmental tumor of the choroid.