SA2RAGE: a new sequence for fast B1+ -mapping

At high magnetic field strengths (≥ 3T), the radiofrequency wavelength used in MRI is of the same order of magnitude of (or smaller than) the typical sample size, making transmit magnetic field (B1+) inhomogeneities more prominent. Methods such as radiofrequency-shimming and transmit SENSE have been proposed to mitigate these undesirable effects. A prerequisite for such approaches is an accurate and rapid characterization of the B1+ field in the organ of interest. In this work, a new phase-sensitive three-dimensional B1+-mapping technique is introduced that allows the acquisition of a 64 × 64 × 8 B1+-map in ≈ 20 s, yielding an accurate mapping of the relative B1+ with a 10-fold dynamic range (0.2-2 times the nominal B1+). Moreover, the predominant use of low flip angle excitations in the presented sequence minimizes specific absorption rate, which is an important asset for in vivo B1+-shimming procedures at high magnetic fields. The proposed methodology was validated in phantom experiments and demonstrated good results in phantom and human B1+-shimming using an 8-channel transmit-receive array.     

Systematic Review and Meta-analysis of Circulatory Disease from Exposure to Low-Level Ionizing Radiation and Estimates of Potential Population Mortality Risks

Background: Although high doses of ionizing radiation have long been linked to circulatory disease, evidence for an association at lower exposures remains controversial. However, recent analyses suggest excess relative risks at occupational exposure levels.Objectives: We performed a systematic review and meta-analysis to summarize information on circulatory disease risks associated with moderate- and low-level whole-body ionizing radiation exposures.Methods: We conducted PubMed/ISI Thomson searches of peer-reviewed papers published since 1990 using the terms “radiation” AND “heart” AND “disease,” OR “radiation” AND “stroke,” OR “radiation” AND “circulatory” AND “disease.” Radiation exposures had to be whole-body, with a cumulative mean dose of < 0.5 Sv, or at a low dose rate (< 10 mSv/day). We estimated population risks of circulatory disease from low-level radiation exposure using excess relative risk estimates from this meta-analysis and current mortality rates for nine major developed countries.Results: Estimated excess population risks for all circulatory diseases combined ranged from 2.5%/Sv [95% confidence interval (CI): 0.8, 4.2] for France to 8.5%/Sv (95% CI: 4.0, 13.0) for Russia.Conclusions: Our review supports an association between circulatory disease mortality and low and moderate doses of ionizing radiation. Our analysis was limited by heterogeneity among studies (particularly for noncardiac end points), the possibility of uncontrolled confounding in some occupational groups by lifestyle factors, and higher dose groups (> 0.5 Sv) generally driving the observed trends. If confirmed, our findings suggest that overall radiation-related mortality is about twice that currently estimated based on estimates for cancer end points alone (which range from 4.2% to 5.6%/Sv for these populations).     

Structural and symptomatic efficacy of glucosamine and chondroitin in knee osteoarthritis: a comprehensive meta-analysis

OBJECTIVE: To assess the structural and symptomatic efficacy of oral glucosamine sulfate and chondroitin sulfate in knee osteoarthritis through independent meta-analyses of their effects on joint space narrowing, Lequesne Index, Western Ontario MacMaster University Osteoarthritis Index (WOMAC), visual analog scale for pain, mobility, safety, and response to treatment. METHODS: An exhaustive systematic research of randomized, placebo-controlled clinical trials published or performed between January 1980 and March 2002 that assessed the efficacy of oral glucosamine or chondroitin on gonarthrosis was performed using MEDLINE, PREMEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Current Contents, BIOSIS Previews, HealthSTAR, EBM Reviews, manual review of the literature and congressional abstracts, and direct contact with the authors and manufacturers of glucosamine and chondroitin. Inclusion, quality scoring, and data abstraction were performed systematically by 2 independent reviewers who were blinded to sources and authors. Conservative approaches were used for clear assessment of potential efficacy. RESULTS: Our results demonstrated a highly significant efficacy of glucosamine on all outcomes, including joint space narrowing and WOMAC. Chondroitin was found to be effective on Lequesne Index, visual analog scale pain, mobility, and responding status. Safety was excellent for both compounds. CONCLUSIONS: Our study demonstrates the structural efficacy of glucosamine and indistinguishable symptomatic efficacies for both compounds. Regarding the relatively sparse data on glucosamine and joint space narrowing and the absence of data on structural effects of chondroitin, further studies are needed to investigate the relationship among time, dose, patient baseline characteristics, and structural efficacy for an accurate, disease-modifying characterization of these 2 compounds.     

Structure of the mature kinetoplastids mitoribosome and insights into its large subunit biogenesis

Kinetoplastids are unicellular eukaryotic parasites responsible for such human pathologies as Chagas disease, sleeping sickness, and leishmaniasis. They have a single large mitochondrion, essential for the parasite survival. In kinetoplastid mitochondria, most of the molecular machineries and gene expression processes have significantly diverged and specialized, with an extreme example being their mitochondrial ribosomes. These large complexes are in charge of translating the few essential mRNAs encoded by mitochondrial genomes. Structural studies performed in Trypanosoma brucei already highlighted the numerous peculiarities of these mitoribosomes and the maturation of their small subunit. However, several important aspects mainly related to the large subunit (LSU) remain elusive, such as the structure and maturation of its ribosomal RNA. Here we present a cryo-electron microscopy study of the protozoans Leishmania tarentolae and Trypanosoma cruzi mitoribosomes. For both species, we obtained the structure of their mature mitoribosomes, complete rRNA of the LSU, as well as previously unidentified ribosomal proteins. In addition, we introduce the structure of an LSU assembly intermediate in the presence of 16 identified maturation factors. These maturation factors act on both the intersubunit and the solvent sides of the LSU, where they refold and chemically modify the rRNA and prevent early translation before full maturation of the LSU.

Kinetoplastids are unicellular eukaryotic parasites, causative agents of several human and livestock pathologies (1). They are potentially lethal, affecting more than 20 million people worldwide (1). Owing in part to their parasitic nature, they strongly diverged from other eukaryotic model species. Kinetoplastids evolved to live in and infect a large variety of eukaryotic organisms in very different molecular environments. Consequently, beyond the general similarities, kinetoplastid species have diverged evolutionarily from one another, and their protein sequence identity can be relatively low. They have a single large mitochondrion, a crucial component of their cellular architecture (2), where gene expression machineries have also largely diverged, notably their mitochondrial ribosomes (mitoribosomes) (3–10). These sophisticated RNA-protein complexes translate the few mRNAs still encoded by mitochondrial genomes. The mitoribosomes’ composition and structure diverged greatly from their bacterial ancestor, with the kinetoplastid mitoribosomes the most extreme case described to date, with highly reduced rRNAs and more than 80 supernumerary ribosomal proteins (r-proteins) compared with bacteria, completely reshaping the overall ribosome structure.Recent structural studies performed in Trypanosoma brucei have highlighted the particularities of this mitoribosome structure and composition, as well as the assembly processes of the small subunit (SSU) (3, 6). However, despite the very comprehensive structural characterization of the full T. brucei SSU and its maturation, several pivotal aspects related to the large subunit (LSU) have remained uncharacterized. For instance, a large portion of the LSU at the intersubunit side, including the whole rRNA peptidyl-transfer center (PTC) along with several r-proteins, were unresolved (3). Moreover, in contrast to the SSU, nearly nothing is known about LSU maturation and assembly. More generally, the maturation of the mitoribosomes in all eukaryotic species remains largely underexplored. Here we present a cryo-electron microscopy (EM) investigation of the full mature mitoribosomes from two different kinetoplastids, Leishmania tarentolae and Trypanosoma cruzi. In addition, we reveal the structure of an assembly intermediate of the LSU displaying unprecedented details on rRNA maturation in these very singular mitoribosomes, some of which likely can be generalized to the maturation of all rRNA.To obtain high-resolution reconstructions of the full kinetoplastid mitoribosomes, we purified mitochondrial vesicles from both L. tarentolae and T. cruzi and directly purified the mitoribosomes from the sucrose gradient (Methods) (SI Appendix, Fig. S1). All of our collected fractions were analyzed by nano-liquid chromatography tandem mass spectrometry (LC-MS/MS) (SI Appendix, Tables S1 and S2) to determine their proteomic composition. We collected micrographs from multiple vitrified samples corresponding to different sucrose gradient density peaks for both species, and following image processing, we obtained cryo-EM reconstructions of the full mitoribosomes, as well as of the dissociated SSU. Moreover, we also derived reconstructions of what appeared to be an assembly intermediate of L. tarentolae LSU. After extensive rounds of two-dimensional (2D) and three-dimensional (3D) classification and refinement we obtained the structure of L. tarentolae and T. cruzi complete and mature mitoribosomes at 3.9 Å and 6 Å, respectively (SI Appendix, Figs. S2–S4). Other notable features include the intersubunit contacts and two distinct rotational states in T. cruzi. Similarly to T. brucei (3), our cryo-EM analysis revealed a reconstruction of an early initiation complex from T. cruzi at 3.1 Å for the body and 3.2 Å for the head of the SSU (SI Appendix, Fig. S5). Further focused refinement on the LSU, SSU head, and SSU body generated reconstructions at 3.6, 3.8, and 4 Å, respectively, for L. tarentolae (SI Appendix, Figs. S2 and S3), and 3.7 and 4.5 Å for T. cruzi LSU and SSU, respectively (SI Appendix, Fig. S4). Combined, these reconstructions, along with the MS data allowed us to build nearly complete atomic models, with only few protein densities remaining unidentified.     

Reconstruction of large defects of the lips and commissure using a composite radial forearm palmaris longus free flap associated with a lengthening temporalis myoplasty

We performed a single-stage operation to reconstruct a large defect of the lips and commissure using a composite radial forearm-palmaris longus free flap. To obtain cranial traction and a voluntary smile, independently from any jaw movement, traction was achieved by using a lengthening temporalis myoplasty. The tendon attached to the coronoid process was fixed to the palmaris longus tendon, recreating a new commissure and a "neo-modiolus." Physical therapy was started on the 21st postoperative day to facilitate progress from a "mandibular smile," to ideally a spontaneous and symmetric smile after 3 months of therapy. This procedure was able to obtain good oral continence and a good commissural movement during smile which has not previously been mentioned in the published literature.     

Effects of lactic acid and glycolic acid on human osteoblasts: a way to understand PLGA involvement in PLGA/calcium phosphate composite failure

The use of degradable composite materials in orthopedics remains a field of intense research due to their ability to support new bone formation and degrade in a controlled manner, broadening their use for orthopedic applications. Poly (lactide-co-glycolide) acid (PLGA), a degradable biopolymer, is now a popular material for different orthopedic applications and is proposed for use in tissue engineering scaffolds either alone or combined with bioactive ceramics. Interference screws composed of calcium phosphates and PLGA are readily available in the market. However, some reports highlight problems of screw migration or aseptic cyst formation following screw degradation. In order to understand these phenomena and to help to improve implant formulation, we have evaluated the effects of PLGA degradation products: lactic acid and glycolic acid on human osteoblasts in vitro. Cell proliferation, differentiation, and matrix mineralization, important for bone healing were studied. It was found that the toxicity of polymer degradation products under buffering conditions was limited to high concentrations. However, non-toxic concentrations led to a decrease in cell proliferation, rapid cell differentiation, and mineralization failure. Calcium, whilst stimulating cell proliferation was not able to overcome the negative effects of high concentrations of lactic and glycolic acids on osteoblasts. These effects help to explain recently reported clinical failures of calcium phosphate/PLGA composites, but further in vitro analyses are needed to mimic the dynamic situation which occurs in the body by, for example, culture of osteoblasts with materials that have been pre-degraded to different extents and thus be able to relate these findings to the degradation studies that have been performed previously.     

Short- and Long-Term Effects on the Ciliary Body and the Aqueous Outflow Pathways of High-Intensity Focused Ultrasound Cyclocoagulation

Several physical methods can be used to coagulate the ciliary body and decrease intra-ocular pressure in patients with glaucoma. The study described here investigated the short- and long-term effects of high-intensity focused ultrasound (HIFU) cyclocoagulation on the aqueous humor production structures and outflow pathways. Thirty-four rabbit eyes were sonicated with a ring-shaped probe containing six miniaturized HIFU transducers. Light, scanning electron and transmission electron microscopy and corrosion casts were performed. In the affected regions, the epithelium of the ciliary processes was degenerated or necrotic and sloughed off. Examinations performed several months afterward revealed involution of the ciliary processes. Vascular corrosion cast revealed focal interruption of the ciliary body microvasculature. In most animals, a sustained fluid space was seen between the sclera, the ciliary body and the choroid, likely indicating an increase in the aqueous outflow by the uveoscleral pathway. These results suggest that HIFU cyclocoagulation has a dual effect on aqueous humor dynamics.