MR perfusion imaging using encapsulated laser-polarized 3He.

In this work, the use of a new carrier agent for intravascular laser-polarized 3He imaging is reported. Lipid-based helium microbubbles were investigated. Their average diameter of 3 microm, which is smaller than that of the capillaries, makes it possible to conduct in vivo studies. The NMR relaxation parameters T1, T2, and T2* of a microbubble suspension were measured as 90 s, 300 ms, and 4.5 ms, respectively, and in vivo images of encapsulated 3He with signal-to-noise ratios (SNRs) larger than 30 were acquired. Dynamic cardiac images and vascular images of encapsulated 3He were obtained in rats using intravenous injections of microbubble suspensions. Excellent preservation of 3He polarization through the lung capillaries and heart cavities was observed. The first images of 3He microbubble distributions in the lungs were obtained. Additionally, the potential of this technique for lung perfusion assessment was validated through an experimental embolism model with the visualization of perfusion defects.

Vascular and perfusion imaging using encapsulated laser-polarized helium.

In this work, the use of hyperpolarized (HP) 3He for in vivo intravascular imaging on animal is reported. To overcome the problem of the low solubility of helium in blood, we propose an approach based on helium encapsulation in lipid-based carrier agents. The mean diameter of the 3He microbubbles, measured equal to 3.0+/-0.2 microm, makes it possible to conduct in vivo studies. In vitro spectroscopy yielded a longitudinal relaxation time T(1) equal to 90 s and an apparent transverse relaxation time T(2)(*) of 4.5 ms. Angiographic imaging (venous and cardiac cavity visualization), as well as lung perfusion imaging, were demonstrated in rats using intravenous injections of microbubble suspensions. Suitable signal and spatial resolution were achieved. The potential of this technique for lung perfusion assessment was assessed using an experimental animal embolism model. Lung perfusion defects and recovery towards a normal perfusion state were visualized. This study was completed with the demonstration of a new ventilation-perfusion lung exploration method based entirely on HP 3He.

BR1: a new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles.

RATIONALE AND OBJECTIVES: The basic characteristics of BR1, a novel echo contrast agent based on stabilized sulfur hexafluoride (SF6) microbubbles have been evaluated. METHODS: The authors determined the physicochemical properties (bubble concentration, bubble size distribution, resistance to pressure, and stability) and the acoustic properties (backscatter and attenuation coefficients) of BR1. The diagnostic value of BR1 was evaluated further in minipigs. Left heart images were recorded before and after injection of different doses of BR1. RESULTS: BR1 is formulated as a lyophilized product, which after addition of saline, provides a suspension containing 2 x 10(8) SF6 microbubbles/mL with a number mean diameter of 2.5 microns. More than 90% of the bubbles are below 8 microns. The use of SF6 rather than air provides an improved resistance to pressure increases such as the ones occuring in the left heart during systole. After reconstitution, the echogenicity and the bubble characteristics are unchanged for more than 8 hours. The high echogenicity remains almost constant over the entire medical frequency range (1-10 MHz). BR1 injections in animals resulted in a homogenous, dose-dependent opacification of the left heart. CONCLUSIONS: Considering its high echogenicity, outstanding stability, and resistance to pressure changes, BR1 is a very promising ultrasound contrast agent.

Heat-regulated expression of the hepatitis B virus surface antigen in the human Wish cell line.

The DNA fragment coding for the hepatitis B virus surface antigen (HBsAg) was placed under the control of a human 70 kDa heat-shock protein (hsp70) promotor sequence. This plasmid construct has been used in transfection experiments to establish a stable amnion cell line of human origin (Wish), expressing an HBsAg in a heat-regulated fashion. Post-translational modifications, such as assembly, glycosylation, secretion and production of both major and middle S proteins appear to function normally. In addition, production of HBsAg under various protocols of heat induction is described. After inoculation into nude mice, development of tumours has been observed at the site of injection. Tumour cells, dispersed by means of collagenase or trypsin treatment from excised tumours, and subsequently seeded into Petri dishes, were able to secrete the same quantities of HBsAg after heat induction as were cells of the original cell line.

[Importance of the study of allergy and determination of the HLA group in the lipoid nephrosis in children. Study of 8 cases]. / Intérêt de la recherche d'une allergie et de la détermination du groupe HLA dans la néphrose lipoidique de l'enfant. Etude de 8 cas.

Eight children with steroid-response nephrotic syndrome were investigated to study the relation-ship between steroid responsive syndrome, allergy and HLA-antigens. Six of them had clinical and/or biological allergic symptoms. The allergen was identified in four out of six cases (grass-pollen 2 cases, house dust 1 case, frullania 1 case). Six children had DR7 HLA-antigen, five had B12 antigen. Three of the four children with cortico-dependent nephrotic syndrome have associated B12-DR7 HLA antigens. Search of an allergen seems to be of interest in children with steroid-responsive nephrotic syndrome, since eviction of the allergen may be proposed as a complement to cortico-therapy.

High-level, heat-regulated synthesis of proteins in eukaryotic cells.

Plasmids have been constructed in which promoters of 70-kDa heat-shock protein genes (hsp70) of human and Drosophila origin were linked to three different eukaryotic genes encoding human growth hormone (hGH), chicken lysozyme (cL) and a human influenza haemagglutinin (HA). Following transfection into widely divergent eukaryotic cells, the hybrid genes direct the transient, heat-regulated synthesis of the three proteins. hGH and cL are secreted into the medium. A human hsp70-hGH construct was used to establish stable mouse fibroblast lines that are capable of producing and secreting hGH at high levels following heat induction: hGH is secreted at a 500-1200-fold higher rate by heat-treated than by untreated cells.