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Biomedical subjects

E Blanc

Publications and source records attributed to E Blanc.

At least 19 recordsLinked to original sources

[Retroperitoneal fibrosis, an unrecognized inflammatory disease. Clinical observations and review of the literature].

Retroperitoneal fibrosis (RF) is a rare disease, typically with an insidious clinical course. The peak incidence is seen in patients 40 to 60 years of age and mostly in man. The characteristic finding in this disease is a periaortic fibrous mass that often surrounds the ureters. Although usually regarded as an obstructive uropathy, there has been growing recognition of the condition as a generalized disease. It may have a wide variety of manifestations including mediastinitis, thyroiditis and sclerosing cholangitis. The most common mode of presentation remains abdominal or flank pain with uremia, anemia and a high sedimentation rate. Although ultrasound and renal scintigraphy may contribute to the general evaluation of patients with RF, CT-scanner is the preferred imaging method. The multiplanar imaging capability of magnetic resonance may facilitate assessment of disease extent. The pathogenesis of the disease remains unknown. Steroids and, more recently tamoxifen, appear to be effective in the treatment of the RF. In most instances, RF does not lead to long-term morbidity or affect survival. The three cases of RF reported herein illustrate the varied mode of presentation and the response to the treatment.

Aged↗

High-resolution experimental phases for tryptophanyl-tRNA synthetase (TrpRS) complexed with tryptophanyl-5'AMP.

Native data, anomalous data at three wavelengths and an independent peak-wavelength data set for SeMet-substituted protein have been collected from cryoprotected crystals of the TrpRS-adenylate product (TAM) complex to a resolution limit of 1.7 A. Independent phase sets were developed using SHARP and improved by solvent flipping with SOLOMON using molecular envelopes derived from experimental densities for, respectively, peak-wavelength SAD data from four different crystals, MAD data and their M(S)IRAS combinations with native data. Hendrickson-Lattman phase-probability coefficients from each phase set were used in BUSTER to drive maximum-likelihood refinements of well defined parts of the previously refined room-temperature 2.9 A structure. Maximum-entropy completion followed by manual rebuilding was then used to generate a model for the missing segments, bound ligand and solvent molecules. Surprisingly, peak-wavelength SAD experiments produced the smallest phase errors relative to the refined structures. Selenomethionylated models deviate from one another by 0.25 A and from the native model by 0.38 A, but all have r.m.s. deviations of approximately 1.0 A from the 2.9 A model. Difference Fourier calculations between amplitudes from the 300 K experiment and the new amplitudes at 100 K using 1.7 A model phases show no significant structural changes arising from temperature variation or addition of cryoprotectant. The main differences between low- and high-resolution structures arise from correcting side-chain rotamers in the core of the protein as well as on the surface. These changes improve various structure-validation criteria.

Crystallization↗

[A functional gene map is required to adapt therapy of metastatic neuroblastoma].

Neuroblastoma is a very common solid tumor which arises in childhood and shows an extreme heterogeneity at the clinical, histological and genetic levels. Besides age and stage, N-myc amplification and 1p deletion are prognostic factors of the disease: in Europe, these genetic markers are used to conduct therapy. In France, N-myc amplification is a factor of bad prognosis which leads, in all forms of the disease including localised forms and metastatic forms of children aged of less than 1 year, to a myeloablative treatment with autologous hematopoietic stem cells transplantation. By contrast, N-myc amplification has no impact on the survival of children aged of more than 1 year with a poor prognosis (30% overall survival, 5 years) but this genetic abnormality is taken into account to treat primary tumor of these patients. In an attempt to find out prognostic factors of these aggressive forms of the disease, various pathways (apoptosis, differentiation angiogenesis, detoxication, immune response) have been recently surveyed, but studies have been carried out on a limited number of genes. Moreover, experimental models of human metastatic neuroblastoma have been obtained in which variations of genes transcript levels involved in these pathways, are observed. The current break-through of cDNA microarrays allows to develop a dynamic transcriptomic scanning of these models as well as of tumors and bone marrows from patients upon conventional chemotherapy. This technology will enable: i) to define molecular entities of the metastatic disease; ii) to apply adapted treatment; iii) to develop new therapeutic strategies.

Age Factors↗

A new fold in the scorpion toxin family, associated with an activity on a ryanodine-sensitive calcium channel.

We determined the structure in solution by (1)H two-dimensional NMR of Maurocalcine from the venom of Scorpio maurus. This toxin has been demonstrated to be a potent effector of ryanodyne-sensitive calcium channel from skeletal muscles. This is the first description of a scorpion toxin which folds following the Inhibitor Cystine Knot fold (ICK) already described for numerous toxic and inhibitory peptides, as well as for various protease inhibitors. Its three dimensional structure consists of a compact disulfide-bonded core from which emerge loops and the N-terminus. A double-stranded antiparallel beta-sheet comprises residues 20-23 and 30-33. A third extended strand (residues 9-11) is perpendicular to the beta-sheet. Maurocalcine structure mimics the activating segment of the dihydropyridine receptor II-III loop and is therefore potentially useful for dihydropyridine receptor/ryanodine receptor interaction studies. Proteins 2000;40:436-442.

Amino Acid Sequence↗

Solution structure of BmKTX, a K+ blocker toxin from the Chinese scorpion Buthus Martensi.

BmKTX is a toxin recently purified from the venom of Buthus Martensi, which belongs to the kaliotoxin family. We have determined its solution structure by use of conventional two-dimensional NMR techniques followed by distance-geometry and energy minimization. The calculated structure is composed of a short alpha-helix (residues 14 to 20) connected by a tight turn to a two-stranded antiparallel beta-sheet (sequences 25-27 and 32-34). The beta-turn connecting these strands belongs to type I. The N-terminal segment (sequence 1 to 8) runs parallel to the beta-sheet although it cannot be considered as a third strand. Comparison of the conformation of BmKTX and toxins of the kaliotoxin family clearly demonstrates that they are highly related. Therefore, analysis of the residues belonging to the interacting surface of those toxins allows us to propose a functional map of BmKTX slightly different from the one of KTX and AgTX2, which may explain the variations in affinities of these toxins towards the Kv1.3 channels.

Amino Acid Sequence↗

Orientational disorder as a function of temperature in the clathrate structure of hydroquinone and C60

In the compound [C(6)H(6)O(2)](3)C(60), hydroquinone (C(6)H(6)O(2)) forms a three-dimensional hydrogen-bonded network enclosing roughly spherical cages with point symmetry 3;m and a diameter of 13.2 A at 100 K. Although C(60) fits tightly into these cages, it shows threefold orientational disorder, the molecular site symmetry being 2/m. The disorder has been studied with single-crystal Mo Kalpha X-ray data at four temperatures, 100, 200, 293 and 373 K. In the refinement, C(60) was restrained to the icosahedral molecular symmetry m3;5; and to rigid-body translational and librational displacements including third- and fourth-order cumulants to account for curvilinear atomic movements, R(|F|) = 3.2-4.7%. At 100 K, bond lengths in C(60) refine to the expected values 1.450 (1) and 1.388 (1) A. The ratio of these values increases with increasing temperature, but the radius of the molecule remains constant at 3. 537 (2) A. The r.m.s. libration amplitudes of C(60) are relatively small (5.5 degrees at 373 K) and the probability function of orientations of C(60) inside the cage shows large values only at the refined positions, indicating that the energy barrier of reorientation is large. Refinement of an ordered twinned structure was unsuccessful; the orientations of neighboring C(60) appear to be uncorrelated.

Journal Article↗

Modelling prior distributions of atoms for macromolecular refinement and completion.

Until modelling is complete, macromolecular structures are refined in the absence of a model for some of the atoms in the crystal. Techniques for defining positional probability distributions of atoms, and using them to model the missing part of a macromolecular crystal structure and the bulk solvent, are described. The starting information may consist of either a tentative structural model for the missing atoms or an electron-density map. During structure completion and refinement, the use of probability distributions enables the retention of low-resolution phase information while avoiding premature commitment to uncertain higher resolution features. Homographic exponential modelling is proposed as a flexible, compact and robust parametrization that proves to be superior to a traditional Fourier expansion in approximating a model protein envelope. The homographic exponential model also has potential applications to ab initio phasing of Fourier amplitudes associated with macromolecular envelopes.

Animals↗

Extensive biopsy protocol improves the detection rate of prostate cancer.

PURPOSE: We evaluated improvement in the rate of prostate cancer detection when using an extensive biopsy protocol involving peripheral cores. MATERIALS AND METHODS: We prospectively evaluated 303 consecutive men who underwent transrectal ultrasound guided biopsy due to elevated prostate specific antigen (PSA) and/or abnormal digital rectal examination. Ten biopsies were performed, including at least 5 at the base and middle of each lobe. In addition to standard biopsy at a 45-degree angle, a more peripheral 30-degree angle biopsy was obtained. At the apex only 1 standard biopsy was done. However, when prostate volume was greater than 50 cm.3, an additional peripheral biopsy was obtained at the apex. RESULTS: The complication rate in this biopsy protocol was 1% (3 patients). Prostate cancer was detected in 118 of the 303 men (38. 9%). Overall this extensive protocol resulted in 6.6% improvement in the detection rate. Improvement was 6.5% in men with PSA 10 ng./ml. or less and 7% in those with PSA greater than 10 (not significant). CONCLUSIONS: Increasing the number of biopsy cores and improving prostate peripheral zone sampling resulted in a significant improvement in the detection of prostate cancer.

Adult↗

Developmental study of rat vestibular neuronal circuits during a spaceflight of 17 days.

The aim of this study was to investigate the potential plasticity of the vestibular system, in structural and biochemical terms, at the level of the gravity receptors (the sensory hair cells), the primary neurons relaying the sensory signals (the vestibular ganglion neurons) and their projections into the vestibular nuclei. We studied the biochemical differentiation of the sensory cells and of the vestibular ganglion by investigating which calcium-binding proteins were present. We studied the development of peripheral synaptic connections of the efferent system by investigating the distribution of CGRP (calcitonin-gene related-peptide) and we also studied the cerebellar synaptic connections in the vestibular nuclei, as identified by the presence of calbindin. Putative changes were studied after a 17-day episode of microgravity (Neurolab STS-90), in developing rats between postnatal days 8 and 25. The extent to which these changes could be caused by alterations in gravity was determined by examining sensory and nervous structures not involved in gravity detection, the cochlea and the cochlear nuclei.

Acoustic Maculae↗

Solution structure of potassium channel-inhibiting scorpion toxin Lq2.

Lq2 is a unique scorpion toxin. Acting from the extracellular side, Lq2 blocks the ion conduction pore in not only the voltage- and Ca2+ -activated channels, but also the inward-rectifier K+ channels. This finding argues that the three-dimensional structures of the pores in these K+ channels are similar. However, the amino acid sequences that form the external part of the pore are minimally conserved among the various classes of K+ channels. Because Lq2 can bind to all the three classes of K+ channels, we can use Lq2 as a structural probe to examine how the non-conserved pore-forming sequences are arranged in space to form similar pore structures. In the present study, we determined the three-dimensional structure of Lq2 using nuclear magnetic resonance (NMR) techniques. Lq2 consists of an alpha-helix (residues S10 to L20) and a beta-sheet, connected by an alphabeta3 loop (residues N22 to N24). The beta-sheet has two well-defined anti-parallel strands (residues G26 to M29 and residues K32 to C35), which are connected by a type I' beta-turn centered between residues N30 and K31. The N-terminal segment (residues Z1 to T8) appears to form a quasi-third strand of the beta-sheet.

Amino Acids↗

Improved free R factors for cross-validation of macromolecular structure - importance for real-space refinement.

Improvements in free R cross-validation are based on changed scaling procedures and the use, in map calculation, of estimates of the validation amplitudes which are independent of the actual observed values. The deleterious effects of the omitted test data are mitigated by reduction of the test-set size, which is made possible by constraining test and working sets to share the same scaling coefficients, thereby reducing the degrees of freedom and the dependence of free R on data selection. Further improvements come with use of a modified free R factor, R freeTA. Instead of omitting the validation reflections from map calculation, their amplitudes are replaced by the average of resolution peers that is (nearly) independent of the actual cross-validation amplitudes. The improvements are relevant to model building, phase refinement by density modification and especially to real-space refinement. Although for real data at about 3 A resolution, free R factors of about 0.25 are affected little, the precision of the structure is improved by about 0.1 A. Tests with simulated data show that with good agreement between observed and calculated amplitudes (as in very high resolution studies or simulated refinement tests), free R factors can be improved by factors greater than two.

Crystallography, X-Ray↗

Real-space molecular-dynamics structure refinement.

Real-space targets and molecular-dynamics search protocols have been combined to improve the convergence of macromolecular atomic refinement. This was accomplished by providing a local real-space target function for the molecular-dynamics program X-PLOR. With poor isomorphous replacement experimental phases, molecular dynamics does not improve real-space refinement. However, with high-quality anomalous diffraction phases convergence is improved at the start of refinement, and torsion-angle real-space molecular dynamics performs better than other available least-squares or maximum-likelihood methods in real or reciprocal space. It is shown that the improvements result from an optimization method that can escape local minima and from a reduction of overfitting through the implicit use of phases and through use of a local refinement in which errors in remote parts of the structure cannot be mutually compensating.

Hydroxymethylglutaryl CoA Reductases↗