Design and development of a robotized system coupled to µCT imaging for intratumoral drug evaluation in a HCC mouse model.

Hepatocellular carcinoma (HCC) is one of the most common cancer related deaths worldwide. One of the main challenges in cancer treatment is drug delivery to target cancer cells specifically. Preclinical evaluation of intratumoral drugs in orthotopic liver cancer mouse models is difficult, as percutaneous injection hardly can be precisely performed manually.

Design and in vivo evaluation of a robotized needle insertion system for small animals.

The development of imaging devices adapted to small animals has opened the way to image-guided procedures in biomedical research. In this paper, we focus on automated procedures to study the effects of the recurrent administration of substances to the same animal over time. A dedicated system and the associated workflow have been designed to percutaneously position a needle into the abdominal organs of mice.

Automatic tracking of an organ section with an ultrasound probe: compensation of respiratory motion.

In minimally invasive surgery or needle insertion procedures, the ultrasound imaging can easily and safely be used to visualize the target to reach. However the manual stabilization of the view of this target, which undergoes the physiological motions of the patient, can be a challenge for the surgeon. In this paper, we propose to perform this stabilization with a robotic arm equipped with a 2D ultrasound probe.

An active cardiac stabilizer based on gyroscopic effect.

Active cardiac stabilization has a role to play in the development of minimally invasive techniques for beating heart surgery. We propose here a new active cardiac stabilization device based on gyroscopic actuation. This system allows to compensate for heart motion in high frequencies and is fully independant and pluggable on conventional stabilizers.

Motion prediction for computer-assisted beating heart surgery.

Off-pump totally endoscopic coronary artery bypass grafting is a milestone for cardiac surgery, and still a technical challenge. Indeed, the fast and complex cardiac motion makes this operating method technically demanding. Therefore, several robotic systems have been designed to assist the surgeons by compensating for the cardiac motion and providing a virtually motionless operating area.

A patient-mounted robotic platform for CT-scan guided procedures.

In this paper, we present a novel robotic assistant dedicated to medical interventions under computed tomography scan guidance. This compact and lightweight patient-mounted robot is designed so as to fulfill the requirements of most interventional radiology procedures. It is built from an original 5 DOF parallel structure with a semispherical workspace, particularly well suited to CT-scan interventional procedures.

Cardiolock: an active cardiac stabilizer. First in vivo experiments using a new robotized device.

Off-pump Coronary Artery Bypass Grafting (CABG) is still a technically difficult procedure. The mechanical stabilizers used for local suppression of the heart excursion have been demonstrated to exhibit significant residual motion, which could lead to a lack of accuracy in performing the surgical task, particularly when using a minimally invasive surgery (MIS) approach. We therefore propose a novel active stabilizer to compensate for the residual motion whose architecture is compatible with MIS.

Cardiolock: an active cardiac stabilizer. First in vivo experiments using a new robotized device.

Off-pump Coronary Artery Bypass Grafting (CABG) is still today a technically difficult procedure. In fact, the mechanical stabilizers used to locally suppress the heart excursion have been demonstrated to exhibit significant residual motion. We therefore propose a novel active stabilizer which is able to compensate for this residual motion.

Fully automated image-guided needle insertion: application to small animal biopsies.

The study of biological process evolution in small animals requires time-consuming and expansive analyses of a large population of animals. Serial analyses of the same animal is potentially a great alternative. However non-invasive procedures must be set up, to retrieve valuable tissue samples from precisely defined areas in living animals.

Towards robotized beating heart TECABG: assessment of the heart dynamics using high-speed vision.

Active robotic filtering is probably the solution for beating heart Totally Endoscopic Coronary Artery Bypass Grafting (TECABG). In this work, we assess the heart motion dynamics by simultaneous use of high-speed imaging of optical markers attached to the heart, ECG signals and ventilator airflow acquisitions. Our goal is to assess the heart motions (shape, velocity, acceleration) in order to be able to make more accurate specifications for a novel, dedicated robot that could follow these motions in real time.

Toward robotized beating heart TECABG: assessment of the heart dynamics using high-speed vision.

Active robotic filtering is a promising solution for beating heart Totally Endoscopic Coronary Artery Bypass Grafting (TECABG). n this work, we assess the heart motion dynamics using simultaneously igh speed imaging of optical markers attached to the heart, ECG signals and ventilator airflow acquisitions. Our goal is to make an assessment of the heart motion (shape, velocity, acceleration) in order to be able to make more accurate specifications for a dedicated robot that could follow this motion in real-time.

The structure of an AspRS-tRNA(Asp) complex reveals a tRNA-dependent control mechanism.

The 2.6 A resolution crystal structure of an inactive complex between yeast tRNA(Asp) and Escherichia coli aspartyl-tRNA synthetase reveals the molecular details of a tRNA-induced mechanism that controls the specificity of the reaction. The dimer is asymmetric, with only one of the two bound tRNAs entering the active site cleft of its subunit.

In vivo selection of lethal mutations reveals two functional domains in arginyl-tRNA synthetase.

Using random mutagenesis and a genetic screening in yeast, we isolated 26 mutations that inactivate Saccharomyces cerevisiae arginyl-tRNA synthetase (ArgRS). The mutations were identified and the kinetic parameters of the corresponding proteins were tested after purification of the expression products in Escherichia coli. The effects were interpreted in the light of the crystal structure of ArgRS.

A single base substitution in the variable pocket of yeast tRNA(Arg) eliminates species-specific aminoacylation.

Early biochemical data showed that aminoacyl-tRNA synthetases often displayed species-specific recognition of tRNA. We compared the ability of purified Saccharomyces cerevisiae and Escherichia coli arginyl-tRNA synthetases to aminoacylate native and transcribed yeast tRNA(Arg) as well as E. coli tRNA(Arg).

Yeast aspartyl-tRNA synthetase residues interacting with tRNA(Asp) identity bases connectively contribute to tRNA(Asp) binding in the ground and transition-state complex and discriminate against non-cognate tRNAs.

Crystallographic studies of the aspartyl-tRNA synthetase-tRNA(Asp)complex from yeast identified on the enzyme a number of residues potentially able to interact with tRNA(Asp). Alanine replacement of these residues (thought to disrupt the interactions) was used in the present study to evaluate their importance in tRNA(Asp)recognition and acylation. The results showed that contacts with the acceptor A of tRNA(Asp)by amino acid residues interacting through their side-chain occur only in the acylation transition state, whereas those located near the G73 discriminator base occur also during initial binding of tRNA(Asp).

Active site mapping of yeast aspartyl-tRNA synthetase by in vivo selection of enzyme mutations lethal for cell growth.

The active site of yeast aspartyl-tRNA synthetase has been characterised by structural and functional approaches. However, residues or structural elements that indirectly contribute to the active site organisation have still to be described. They have not been assessed by simple analysis of structural data or site-directed mutagenesis analysis, since rational targetting has proven difficult.

L-arginine recognition by yeast arginyl-tRNA synthetase.

The crystal structure of arginyl-tRNA synthetase (ArgRS) from Saccharomyces cerevisiae, a class I aminoacyl-tRNA synthetase (aaRS), with L-arginine bound to the active site has been solved at 2.75 A resolution and refined to a crystallographic R-factor of 19.7%.

Characterization of a thermosensitive Escherichia coli aspartyl-tRNA synthetase mutant.

The Escherichia coli tls-1 strain carrying a mutated aspS gene (coding for aspartyl-tRNA synthetase), which causes a temperature-sensitive growth phenotype, was cloned by PCR, sequenced, and shown to contain a single mutation resulting in substitution by serine of the highly conserved proline 555, which is located in motif 3. When an aspS fragment spanning the codon for proline 555 was transformed into the tls-1 strain, it was shown to restore the wild-type phenotype via homologous recombination with the chromosomal tls-1 allele. The mutated AspRS purified from an overproducing strain displayed marked temperature sensitivity, with half-life values of 22 and 68 min (at 42 degrees C), respectively, for tRNA aminoacylation and ATP/PPi exchange activities.

Selection of tRNA(Asp) amber suppressor mutants having alanine, arginine, glutamine, and lysine identity.

Elements that confer identity to a tRNA in the cellular environment, where all aminoacyl-tRNA synthetases are competing for substrates, may be delineated by in vivo experiments using suppressor tRNAs. Here we describe the selection of active Escherichia coli tRNAAsp amber mutants and analyze their identity. Starting from a library containing randomly mutated tRNA(CUA)Asp genes, we isolated four amber suppressors presenting either lysine, alanine, or glutamine activity.

Crystallization of Escherichia coli aspartyl-tRNA synthetase in its free state and in a complex with yeast tRNA(Asp).

Overexpressed dimeric E. coli aspartyl-tRNA synthetase (AspRS) has been crystallized in its free state and complexed with yeast tRNA(Asp). Triclinic crystals of the enzyme alone (a = 104.

Aspartate identity of transfer RNAs.

Structure/function relationships accounting for specific tRNA charging by class II aspartyl-tRNA synthetases from Saccharomyces cerevisiae, Escherichia coli and Thermus thermophilus are reviewed. Effects directly linked to tRNA features are emphasized and aspects about synthetase contribution in expression of tRNA(Asp) identity are also covered. Major identity nucleotides conferring aspartate specificity to yeast, E coli and T thermophilus tRNAs comprise G34, U35, C36, C38 and G73, a set of nucleotides conserved in tRNA(Asp) molecules of other biological origin.

The class II aminoacyl-tRNA synthetases and their active site: evolutionary conservation of an ATP binding site.

Previous sequence analyses have suggested the existence of two distinct classes of aminoacyl-tRNA synthetase. The partition was established on the basis of exclusive sets of sequence motifs (Eriani et al. [1990] Nature 347:203-306).

Genetic selection for active E.coli amber tRNA(Asn) exclusively led to glutamine inserting suppressors.

Suppressor tRNAs are useful tools for determining identity elements which define recognition of tRNAs in vivo by their cognate aminoacyl-tRNA synthetases. This study was aimed at the isolation of active amber tRNA(Asn). Nineteen mutated tRNA(Asn)CUA having amber suppressor activity were selected by an in vivo genetic screen, and all exclusively inserted glutamine.

Transfer RNA binding protein in the nucleus of Saccharomyces cerevisiae.

A yeast nuclear protein that binds to tRNA was identified using a RNA mobility shift assay. Northwestern blotting and N-terminal sequencing experiments indicate that this tRNA-binding protein is identical to zuotin which has previously been shown to bind to Z-DNA [(1992) EMBO J. 11, 3787-3796].