Local hyperthermia with MR-guided focused ultrasound: spiral trajectory of the focal point optimized for temperature uniformity in the target region.

The objective of hyperthermia treatment is to deliver a similar therapeutic thermal dose throughout the target volume within a minimum amount of time. We describe a noninvasive approach to this goal based on magnetic resonance imaging (MRI)-guided focused ultrasound (FUS) with a spherical transducer that can be moved along two directions inside the bed of a clinical MR imager and that has an adjustable focal length in the third dimension. Absorption of FUS gives rise to a highly localized thermal buildup, which then spreads by heat diffusion and blood perfusion. A uniform temperature within a large target volume can be obtained using a double spiral trajectory of the transducer focal point together with constant and maximum FUS power. Differences between the real and target temperatures during the first spiral are evaluated in real time with temperature MRI and corrected for during the second spiral trajectory employing FUS focal point velocity modulation. Once a uniform temperature distribution is reached within the entire volume, FUS heating is applied only at the region's boundaries to maintain the raised temperature levels. Heat conduction, together with the design and timing of the trajectories, therefore ensures a similar thermal dose for the entire target region. Good agreement is obtained between theory and experimental results in vitro on gel phantoms, ex vivo on meat samples, and in vivo on rabbit thigh muscle. Edema in muscle was visible 1 hour after hyperthermia as a spatially uniform rise of the signal intensity in T(2)-weighted images.

N-acetyl-heparosan lyase of Escherichia coli K5: gene cloning and expression.

The structure of the capsular polysaccharide of Escherichia coli K5 is identical to that of N-acetyl-heparosan, a nonsulfated precursor of heparin, which makes this E. coli antigen an attractive starting point for the chemical synthesis of analogs of low-molecular-weight heparin. This polysaccharide is synthesized as a high-molecular-weight molecule that can be depolymerized by an enzyme displaying endo-beta-eliminase activity. The eliminase-encoding gene, designated elmA, has been cloned from E. coli K5 by expression in E. coli K-12. The K-12 genome is devoid of the elmA sequence. The elmA gene product is 820 amino acids long. Active recombinant eliminase is produced by K-12 cells in both cell-bound and secreted forms. Deletion analyses have shown that the C terminus and the N terminus are required for activity and secretion, respectively.

Primary cutaneous nocardiosis caused by Nocardia otitidiscaviarum: two cases and a review of the literature.

We report two cases of primary cutaneous nocardiosis due to Nocardia otitidiscaviarum. The first case is a mycetoma, the second, a cutaneous abcess: these two cases were imported into France (Vietnam, Zimbabwe). The literature on primary cutaneous nocardiosis due to N. otitidiscaviarum is reviewed.

Adaptive predictive control of dissolved oxygen concentration in a laboratory-scale bioreactor.

We present an algorithm for the adaptive control of dissolved oxygen concentration in a bioreactor, based on the agitation rate. The dynamics are represented by an incremental first-order model with variable dead-time and parameters. These are estimated on-line by a recursive least-squares identification method with a forgetting factor and a constant sensitivity. The model is employed to predict the behaviour of the dissolved oxygen concentration over a finite horizon, using an original method which requires little computation. Then, a Generalized Predictive Control optimisation strategy computes the agitation rate from the predictions and the desired set point, while gradually updating the controller smoothness. This algorithm, which requires little preliminary knowledge, has been implemented on a laboratory-scale fed-batch bioreactor for which the use of conventional controllers showed limited performance, due to the unpredictable and evolutive nature of the dynamics. The new controller proved to be robust and effective over a wide range of operating conditions, while requiring no operator adjustments.

Biologically active A-chain of the plant toxin ricin expressed from a synthetic gene in Escherichia coli.

To assess the biological activity and pharmacokinetic properties of nonglycosylated ricin A-chain (RA), we have obtained the polypeptide following expression of a synthetic 842-bp RA gene in Escherichia coli. Expression of the gene was carried out using the phage T5 PN25 promoter fused to the E. coli lac operator. The RA polypeptide was synthesized in a completely soluble form and was purified in one step by immunoabsorption. It was shown to be as cytotoxic for a human cell line as both native RA and chemically deglycosylated native RA. Reconstituted whole ricin and an immunotoxin containing the recombinant RA were also biologically active. Immunotoxins made with recombinant and deglycosylated RA had similar clearance rates in vivo showing, after a short period of rapid elimination, stabilities far higher than that of an immunotoxin made with native RA. Our results show that the complete elimination of sugar side chains from the RA is not sufficient to entirely eradicate the rapid initial in vivo clearance of RA-based biologicals.

[An experimental study of the stability of Hoffmann's external fixation (author's transl)]. / Stabilité expérimentale du fixateur externe de Hoffmann. Présentation d'un nouveau matériel.

The authors have tested the stability of Hoffmann fixation in relation to the number and location of the fixating pins. A double frame configuration as described by Vidal is not superior since it allows some mobility in the plane of flexion and extension. The authors believe that a double perpendicular plane configuration is more satisfactory without the use of a transfixing pin. This method is more stable. To improve stability in valgus-varus plane, the authors have designed a device which is more rigid and which decreases by 300 per cent any residual mobility at the fracture site. A newly designed plate allows good fixation in the epiphysis. The first clinical cases in which this new fixator has been used have given promising results.

[Complimentary surgical procedures following treatment of non-union by the Papineau method (author's transl)]. / Les gestes complémentaires de l'opération de Papineau.

The authors have treated 82 non-unions by the Papineau method of bone grafting without skin closure. In 30 cases, a complimentary bone procedure had to be performed to reinforce bone union. This consisted of a new Papineau procedure in 18 cases and an iliac graft with skin closure in 12 cases. Infection recurred in several instances. In addition to these 30 cases, 3 secondary fractures were seen. In cases with persistently depressed scars, a fresh Papineau procedure may be needed. In cases with persistent skin ulceration, resection and skin suture should be tried before a cross-leg skin graft. The authors emphasize the frequency of vascular changes which should be looked for by arteriography.

[Rotational displacement of eccentric cups cemented in the acetabulum (author's transl)]. / Rotation anormale de certaines cupules cotyloïdiennes excentrées scellées.

The authors have operated on 15 hips using a total prosthesis comprising a metallic head and plastic cup cemented in the acetabulum. The acetabular component is thicker at its upper part to accommodate eventual wear in the plastic. In all cases the cup rotated through 180 degrees so that, after several months, the thicker part was situated at the lower pole of the acetabulum. In two cases, a fracture of the cup was found. The cause of this abnormal rotation can be explained by a torque action taking place at each step because of the eccentric design of the cup. This was demonstrated by a prosthesis inserted into a cadaver and tested by simulated walking. 45 kilometres of walking were sufficient to provoke a rotation of 90 degrees. Conclusions are given on the use of such eccentric cups which should be avoided.

[Planktonic and bacterial population dynamics during experimental production of natural marine phytoplankton. II. Structure and physiology of populations and their interactions]. / Dynamique des populations planctoniques et bactériennes au cours d'une production expérimentale de phytoplancton marin naturel. II. Structure et physiologie des populations et leurs interactions.

During the spring, an experiment was conducted on the production of natural phytoplankton in a continuous flow layout of large capacity, and an analysis was made of the simultaneous evolution of microplanktonic populations (taxonomic composition, diversity, class ranges, and energetic charge) and of bacterial populations (structure, diversity, dominances, and cetabolic potentialities). Oligotrophic initial conditions were charcterized by a poor (0.22 umg of chlorphyll a/L) and diversified (pigment diversity = 4.5) phytoplankton with nanoplanktonic dominance associated with several benthic type diatoms. Bacterial flora, in which pseudomonads were dominant (54.5%), were also diversified (Shannon index H = 3.57). Metabolic potentialities of these bacterial communities were several. Enrichment of the milieu caused the selection and development of a small number of algal species dominated by the diatoms skeletonema costatum (64 x 106/L) and Chaetoceros (3.2 x 106/L) leading to a paucispecific population with a large biomass, a pigment diversity of 1.97, and a chlorophyll a concentration of 25.08 mu/L. The bacterial community then because diversified (H = 4.12) and, although pseudomonads remained dominant (62%), a larger use of organic micromolecules was noted. The establishment of this phytoplanktonic community was followed by a zooplanktonic development in which larger species succeeded smaller ones (ciliates, tintinnides, rotifers, and copepods) corresponding to the global increase of the phytobiomass. Although this system appeared to be in a phase of relative stability, a decease in the energetic charge showed a disturbance in the physiological state of the planktonic populations. These phenomena led to the vanishing of the diatom's dominance (Chaetoceros, and then S. costatum) and its replacement by nanoplankton (123 x 106 cells/L) and dinoflagellates (300000 cells/L). A modification in the organic wealth of the milieu with the addition of particular complex material that was not or little degraded caused deep disturbances in the bacterial populations. Their diversity reached a very low level (H = 1.56 to 2.25) with a proliferation of vibrions (up to 74%) well equipped with exoenzymes, but more restricted in their nutritional versatility (marked preference for organic macromolecules). During the final phase of experimentation, despite a change in qualitative composition and a more important biomass, microplanktonic and bacterial populations returned to a diversified state nearing that of the initial conditions (pigment diversity = 3.2; H = 3.37).

[Rupture of third duodenum (author's transl)]. / Rupture complète de 3e doudénum. Intervention. Guérison.

The authors report a case of complete rupture of the third duodenum after blind trauma of the abdominal wall. They discuss pre op diagnosis with amount to X ray findings; surgical management included resection of the left part of the 3rd duodenum, 4th duodenum, and 1rst jejunal loop, with latero terminal anastomosis of the lower part of the 2nd duodenum to the jejunum; uneventfull recovery.

[Infected total knee prostheses treated by Papineau's technique and arthrodesis (author's transl)]. / Arthrodèse du genou après ablation de prothèse totale selon une technique inspirée de la méthode de Papineau.

The technique of arthrodesis of the knee after removal of an infected total prostheses is described. It was used in four cases. In the first stage, the prostheses and cement were removed, the wound was left open and knee immobilized by Hoffman external fixation. Details of the fixation are given. The second stage of filling of the wound by cancellous chips was performed two weeks later. On average, the fixation was removed after seven months. Some mechanical experiments were made to establish the best type of fixation device.